Induced Mutation: A New Paradigm in Pulse Weed Control Strategies

Abstract

Pulses hold a remarkable significance by providing affordable source of dietary protein and other vital nutrients. However, various biotic (weeds, pathogens, and insect infestation) and abiotic (temperature, nutrient stress, waterlogging, drought, salinity, and heavy metals) constraints induce substantial harm by decreasing its production. Weeds pose a significant global challenge as these not only compete with crop for vital resources such as sunlight, space, nutrients, and water but also attract other pests and pathogens that can harm the pulse crops. The weed–crop intervention varies significantly based on the crop type, topography, and soil characteristics. The implementation of chemical weed control strategies not only revolutionized the global agriculture but also widely acknowledged as an essential tool in accelerating crop productivity. Pre-emergent herbicides are easy to get in the market; however, the lack of post-emergence herbicides for certain pulses is of primary concern. The use of alternative weed control chemicals not just eradicates weeds but the risk of damaging the pulse crop may persist. The development of herbicide-resistant crop using modern techniques is the current objective of plant researchers. For this aim, induce mutation stands out the most cost-effective and reliable option, which can be accomplished using both physical and chemical mutagens.

1. Introduction

The societal impact of agriculture is evident for upholding livelihood. Therefore, the role of agricultural sector in ensuring global food security is progressively expanding overtime [1]. Various emerging states are so anxious regarding their food security. The risk of decreased global food system is expected to intensify in the forthcoming decades due to the increasing population and the adverse impacts of climate change [2]. Meeting the growing demand for global food consumption in 2050 may require a robust increase in agricultural production, estimated to be around 60–70% by some sources such as Foley et al. and Tilman et al. Alternatively, other studies suggest that food production might need to double by 2050 to adequately address the escalating needs [3].

Pulses are the edible seeds of plants associated with Fabaceae (a.k.a. Leguminosae or Legume Family), constituting one of the most extensive categories of flowering plants with high nutritional values. In the last decade, pulses have emerged as a sustainable choice to meet the rising demand for food. This upswing is perceived as a strategic approach to address the global agricultural challenges [4]. Based on chronological and archeological proof, it is indicated that the domestication and origin of pulses occurred in the America Presently, these are extensively enjoyed worldwide either as dietary staple or incorporated into various cuisine. Areas like Mexico, South and Central America, and various African countries have adopted the pulses as fundamental dietary components, with per capita consumption reaching up to 40 kg per year in certain regions [5]. Pulses emerge as an excellent protein source. Additionally, they supply dietary fiber, starch, minerals, and vitamins (Figure 1). Introducing pulses into your daily diet brings forth numerous health benefits, including the control of various metabolic conditions such as diabetes mellitus, coronary heart disease, and colon cancer [6]. While there is a diversity of pulses based on their varied shapes and sizes, although over 80 species contribute to the human diet and the FAO database encompasses only 11 of them [7] out of which chickpeas (Cicer arietinum), peas (Pisum sativum), lentils (Lens culinaris), mung beans (Vigna radiata), dry broad beans (Vicia faba), moth beans (Vigna aconitifolia), lupins (Lupinus perennis), and mash bean (Vigna mungo) are widely accessible in the market [8].

Figure 1.

Detailed overview on different pulse varieties along with their scientific name, common name, and nutritional profile.

1.1 Trends in global pulse cultivation

According to the current situation of global pulse production, Asia, Europe, and America collectively contribute to more than 80% of the world’s output, with Asia alone contributing over 45% to the total. Additionally, Australia and African nations also contribute to the global production of pulses. Notably, higher production levels are observed in India, China, and Myanmar among Asian countries. India is leading as the primary producer of pulses. As of 2021, the worldwide pulse production reached a cumulative 88.97 million metric tons (Statista 2023) (https://www.statista.com/) from which peas, chickpeas, and dry beans collectively make up about 65% of the overall production of major pulses globally (Figure 2). Researchers have reported specific percentage shares for different varieties: dry beans (32%), peas (19%), chickpeas (14%), cowpea (7%), broad beans (7%), lentils (6%), and other varieties (15%) [9].

Figure 2.

Statistical overview showing worldwide pulse production from past 12 years (Statista 2023).

Weeds are the undesirable flora, detrimental for the optimum growth of plants [10]. Similar to crops, weeds require sunlight and water for photosynthesis, space in the soil for root proliferation, and essential nutrients derived from the soil to facilitate their growth. Consequently, weeds emerge as significant competitors with crops for vital resources [11]. Weed infestation poses a significant challenge in both developed and developing countries. Agricultural losses in developed countries typically fall within the range of 5–10%, whereas in developing or emerging countries, these losses increase to 20–30% [12]. Weeds often serve as alternate hosts for various diseases and insect pests (Figure 3) [13]. Hence, proficient weed control holds the potential to mitigate the risks of diseases and insect pest infestations in crops.

Figure 3.

Pest-induced losses in pulses.

Different pulse crops exhibit varied weed floras, including sedges, broadleaves, and narrow leaves. The type and intensity of weed infestation in field contribute to decline in pulse yield. Herbicides represent a chemical approach to weed control. However, the effectiveness of herbicides depends on dosage, timing, growth stage, and the specific crop being grown. Various commercially available herbicides not only eliminate weeds but also affect desired plants. Presently, researchers are concentrating on developing herbicide tolerance in pulse crops. The objectives for composing this book chapter are as follows:

• To highlight the diverse weed flora and its toxicity in different pulse crops.

• To present chemical method for weed management (its types, groups, merit, and demerits).

• The chapter also depicts the role of induced mutation to enhance the resilience of pulse crops against herbicidal treatments encompassing both physical and chemical mutagens.

• It also explores opportunities for integrating induced mutation techniques with other breeding strategies, such as genome editing, to improve the effectiveness of developing herbicide resistance traits in pulse crops.

• Finally, additional modern approaches in weed control strategies for pulses are discussed, which should be considered alongside induced mutation methods in near future.

2. Methodology

2.1 Search criteria and internet search engines

A detailed search was conducted using Google Scholar and Google Web Browser, employing keywords such as “pulses,” “impact of weeds on pulse crops,” “herbicide-resistant crops,” “herbicide mode of action,” “methods for developing herbicide-resistant crops,” “seed mutagenesis,” “herbicide resistance mechanisms,” “non-chemical weed control practices,” and “induced mutations for herbicide resistance in pulses.” Relevant and up-to-date literature was then carefully scrutinized based on the data relevant to this study. Papers that were outdated or lacked clearly defined results were excluded. A total of 66 peer-reviewed research articles were selected based on their content.

3. Discussion

3.1 Weed interference in pulse crop

Pulses face restricted productivity primarily from various biotic and abiotic factors, with weeds appear as a significant contributor by adversely impacting pulse crop yields. Upon analysis, it becomes evident that the losses in yield attributed to weeds are 34–37% compared to other pests or pathogens. The diversity and abundance of weed species in pulse crops are influenced by soil characteristics, farming practices, and climatic conditions [14]. Different pulses have specific critical periods when they are vulnerable to weed interference (Tables 1 and 2) [15].

Scientific name	Common name	Family	Emergence time	Weed type	Lifecycle
Polypogon monspeliensis*	Rabbit Foot Grass, Green Foxtail, Lomarr Ghas, Beard Grass	Poaceae	Late–Mid October to March	Slender Leaf	Annual
Avena fetua*	Wild Oat, Jangli Jai, Javdri
Sorghum halepense*	Jhonson Grass, Baaro
Echinochloa colona*	Jungle Rice, Swanki Ghas, Jharua, Barnyard Grass
Dactyloctenium aegyptium*	Egyptian Grass, Madhana Ghas
Phalaris minor*	Canary Grass, Bird’s Seed Grass, Dumbi Sitti, Bunch Grass, Sittee Booti
Paspalum dilatatum*	Watre Grass, Naro Ghas
Lolium perenne*	Rye Grass, Rye Ghas
Cynodon dactylon*	Cynodon Dactylon, Khabal Ghas
Digitaria sanguinalis*	Large Crab Grass, Moti Khabal
Avena ludoviciana*	Wild Oats, Jaundhar
Lolium temulentum*	Poison Rye Grass, Ivary, Poson darnel
Poa annua”	Guein, Buein, Sweet Grass, Annual Blue Grass, Annual meadow
Asphodelus tenuifolius*	Wild Onion, Piazi, Bhokat, Jangli Piyaz	Asphodelaceae	November–December	Slender Leaf	Annual
Cyperus rotundus*	Nut Grass, Dela Ghas, Nut Sedge	Cyperaceae	November	Slender Leaf	Annual
Allium canadense*	Wild Onion, Pyaazi	Amaryllidaceae	November–December	Slender Leaf	Annual

Table 1.

Monocot weed flora in pulse field.

This table showcases the monocot weed flora in pulse fields, providing information on their scientific/common names, growing season, weed type, and family. (*) represents the weeds of rabi pulses such as chickpea, lentil, pea, and faba beans while (“) represents the weeds of kharif pulses like black gram, mung bean, cowpea, moth pea, pigeon pea, and kidney beans.

Scientific name	Common name	Family	Emergence time	Weed type	Lifecycle
Euphorbia peplus*	Petty Spurge, Lal Dodhak, Cancer Weed, Radium Weed, Milk Weed	Euphorbiaceae	Mid October–Mid-March	Broad Leaf	Annual
Euphorbia helioscopia*	Mad Woman’s Milk, Sun Spurge, Chatri Dodhak, Dhudi
Euphorbia hirta*	Asthma Plant, Hairy Spurge, Ara Tanah
Euphorbia simplex”	Kuargandal, Leafy Spurge
Chrozophora tinctoria”	Dyer’s Corton, Giradol, Turn Sole
Fumaria indica*	Fumitory, Shihatara, Pitpapra, Fumewort	Papaveraceae	Late December	Broad Leaf	Annual
Fumaria officinalis*	Fumitory, Earth Smoke, Shahtara
Digera muricata*	False Amaranth, Tandala	Amaranthaceae	Mid October- Late December	Broad Leaf	Annual
Chenopodium album*	Common Goosefoot, Baatho, Bathwa, Lambs Quarters
Amaranthus viridis*	Slender Amaranth, Green Amaranth, Jangli Cholai, Pig Weed
Chenopodium murale*	Fat Hen, Karond, Nettle Leaf
Gomphrena globose*	Globe Amaranth
Chenopodium quinoa*	Wild Quinoa
Silybum marianum”	Milk Thistle, Kandyali Dodhak	Asteraceae	October to March	Broad Leaf	Mostly Annual some are Biennial and few are Perennial
Cirsium arvense”	Canada / Creeping Thistle, Field Thistle Leh, Kandyari
Cichorium intybus”	Blue Daisy, Kasni
Carthamus oxycantha”	Wild Safflower, Phooli, Kandiari
Parthenium hysterophorus*	Santa Maria Feverfew, Famine Weed, Gajar Ghas, Dhanura
Sonchus asper*	Spin Sowthistle, Kandiali Dodhak
Sonchus arvensis*	Mil Weed, Perennial Sow Thistle, Gut weed
Gnaphalium purpureum”	Purple Cudweed, Spoon leaf purple everlasting
Synedrella nodiflora”	Cinderella Weed, Nodeweed
Solanum nigrum”	Black Night Shade, Mako/Peelak	Solanaceae	March	Broad Leaf	Annual–Biennial
Corchorus tridens*	Wild Jute, Horn-Fruited Jute, Jangli Patsun	Malvaceae	December	Broad Leaf	Annual/Perennial
Malva parviflora*	Dwarf Mallow, Cheese Weed, Mallow, Sonchal		October
Melilotus indica”	Yellow Sweet Clover, Zard Seenji	Fabaceae	November–February	Broad Leaf	Annual
Lathyrus aphaca”	Crow Pea, Dokanni, Yellow Pea, Yellow Vetchling
Lathyrus sativus*	Grass Pea, Chraal, Kaseeri, White Pea, White Vetch
Medicago polymorphav”	Bur Clover, Maina, Burr medic
Melilotus alba”	White Sweet Clover, Sufaid Senji, Bukhara clover, honey clover
Vicia hirsute”	Rewari, Hairy Vetch, Tiny Vetch
Medicago denticulate*	Maina, Toothed Bur Clover
Trigonella polycerata”	Maini, Wild Fenugreek
Vicia sativa”	Common Vetch, (Broad Leaf), Rewari, Choti Phali
Lathyrus aphaca”	Crow Pea, Jangli Mattar
Coronopus didymus*	Swine Cress, Jangli Halon, Bitter Cress	Brassicaceae	November–January	Broad Leaf	Annual–Biennial
Sinapis arvensis*	Wild Mustard, Jangli Sarsoon, Charlock Mustard, Field Mustard
Lepidium sativum*	Garden Cress, Halon, Cresss
Sisymbrio irio	London Rocket, Khoob Kalan
Ranunculus sceleratus”	Cursed Butterup, celery leaf buttercup	Ranunculaceae	Late January–March	Broad Leaf	Annual
Argemone mexicana”	Satyanasi, Jangli Post, Mexican Poppy, Cardosanto
Stelleria media*	Common Chickweed, Poolan Booti	Caryophyllaceae	Late December–February	Broad Leaf	Annual
Saponaria vaccaria”	Soapwort, Bara Takla, Cow Cockle, Cow basil
Spergula arvensis”	Corn Spurry, Kalri Booti, Jangli Dhania
Silene conoidea”	Chotta Takla, Forked Catchfly
Arenaria serpyllifolia”	Thyme Leaf Sandwort
Antirrhinum orontinum”	Wild Dog Flower Lesser snapdragon, Weasel’s snout	Plantaginaceae	January–February	Broad Leaf	Annual
Veronica agrestis”	Green Field Speedwell
Anagallis arvensis”	Blue Pimpernel, Billi Booti	Primulaceae	January	Broad Leaf	Annual
Convolvulus arvensis*	Field Bindweed, Lehli, Hirankhuri	Convolvulaceae	Late December	Broad Leaf	Perennial
Rumex dentatus”	Broad Leaf Dock, Jangli Palak, Toothed Dock	Polygonaceae	January	Broad Leaf	Annual
Polygonum plebeium*	Prostrate Knotweed, Danak, Hazardani, Machechi, Common knotweed		Early November
Rumex spinosus*	Kandiali Palak, Spiny Dock, Sorrel, Lesser jack		Late December
Heliotropium europaeum”	Heliotrope, Ont Chara	Boraginaceae	January–March	Broad Leaf	Annual
Lithospermum arvense”	Stone Weed, Field gromwell, Bastard alkanet
Tribulus terrestris”	Puncture Vine, Bhakra, Gokharu	Zygophyllaceae	Mid-Late February	Broad Leaf	Annual
Daucus carota”	Wild Carrot, Bishop’s Lace, Queen Anne’s Lace, Jangli Gajjar	Apiaceae	January	Broad Leaf	Biennial
Trianthema portulacastrum*	Desert Horse Purslane, Att Satt	Aizoaceae	Early October	Broad Leaf	Annual
Cleome viscosa*	Yellow Spider Flower, Tick Weed, Hulhul	Cleomaceae	Late October	Broad Leaf	Annual
Galium aparine*	Bed Straw, Couch Weed, Catch Weed, Goosegrass, Warribooti, Cleavers	Rubiaceae	October	Broad Leaf	Annual
Cannabis sativa”	Bhang, Indian Hemp	Cannabaceae	Late December–February	Broad Leaf	Annual
Oenothera laciniata”	Cutleaf Evening Primrose	Onagraceae	February	Broad Leaf	Annual

Table 2.

Dicot weed flora in pulse field.

This table showcases the dicot weed flora in pulse fields, providing information on their scientific/common names, growing season, weed type, and family. (*) represents the weeds of rabi pulses such as chickpea, lentil, pea, and faba beans while (“) represents the weeds of kharif pulses like black gram, mung bean, cowpea, moth pea, pigeon pea, and kidney beans.

3.1.1 Chickpea (Cicer arietinum L.)

Chickpea (Cicer arietinum L.) ranks as the world’s third most vital pulse crop enriched in protein and other vital nutrients. It faces persistent challenges in achieving optimal yield. Among various contributing factors, weed competition plays a pivotal role, causing significant yield losses ranging from 40 to 80%, depending on the severity of weed vegetation and the duration of the infestation. Due to its short stature and slow initial growth, chickpeas face intense competition from weeds, resulting in significant reductions in growth and yield [16]. The grain yield encounters a 17.1% decrease within the initial 30 days of sowing in chickpea as a result of weed competition, which increases to around 50% if weeds persist throughout the entire crop season. The initial 60-day period emerges as a critical phase marked by intense weed–crop competition in chickpea cultivation [17].

3.1.2 Mung bean (Vigna radiata L.)

Mung bean (Vigna radiata L.) is renowned for its exceptional nutritional value, digestibility, and non-flatulent attributes compared to other pulses [18]. The cultivation of mung beans faces significant challenges that can adversely affect production, with weed presence standing out as a major concern. The failure to manage weeds led to a substantial, 31% reduction in mung bean yield. The initial phase of land preparation plays a pivotal role in facilitating optimal plant growth. Weed control strategies involve a variety of approaches, including chemical measures such as the application of oxyflourfen pre-emergent herbicide at an early stage and manual weeding practices at specific growth stages. Oxyflourfen, employed as a pre-emergent herbicide, is utilized post-tillage and before seed planting to impede the growth or germination of weed seeds on the soil surface [19].

3.1.3 Lentil (Lens culinaris Medik)

Lentil (Lens culinaris Medik.), categorized as a minor grain legume, is increasingly gaining attention due to its significance as a vital dietary source of both macro and micronutrients, including essential amino acids. Beyond its nutritional richness, consumers value lentils for their appealing taste and ease of preparation. Although lentil production and consumption have been on the rise across Europe in recent decades, a considerable portion of the demand is fulfilled by imports from countries outside the European Union (EU) [20].

The robust interference of weeds in the initial stages of the lentil crop growth significantly hampers the plant’s growth and development, resulting in reduced yield and overall quality. Depending on environmental conditions, weed diversity, and density, the associated losses can vary within the range of 20–80%. Conventional practices, including strategic sowing methods and timing, utilization of cover crops, implementation of crop rotations, and careful varietal selection, are routinely employed to impede weed growth and biomass, consequently enhancing lentil yields. Currently, herbicide treatments also demonstrate notably high effectiveness compared to other methods [21].

3.1.4 Mash bean (Vigna mungo L.)

Mash bean (Vigna mungo L.) stands out among leguminous crops, owing to its high protein and vitamin content, nutritional superiority, and rapid cooking time. Several factors contribute to the low yield of black gram, with weeds being identified as the most significant among them. The crop faces challenges in competing with weeds, particularly in its early stages of growth. Black gram is typically cultivated in rainfed conditions during the kharif season, where weeds emerge as a primary factor affecting crop productivity negatively. Weed competition during critical periods can lead to substantial yield reductions, ranging from 80 to 90%, depending on the type and intensity of weed infestation. Uncontrolled weed growth has been documented to result in a considerable reduction (46–53%) in black gram seed yield. Traditional methods like hand weeding are effective, and they are also expensive, labor-intensive, and time-consuming. As a response, weed control in black gram involves the application of mechanical, chemical, and biological methods, either individually or in combination with one another [22].

3.1.5 Faba beans (Vicia faba L.)

Faba bean (Vicia faba L.) holds significant importance as a primary food legume crop, serving as a valuable source of dietary protein. This legume is highly sensitive to shading especially during the pod emergence stage [23]. Faba beans face a considerable challenge from weeds, leading to yield losses ranging from 15 to 50% and contributing to annual global economic losses surpassing US$100 billion. The competition with weeds poses a significant obstacle to faba bean production, especially during critical developmental stages, resulting in substantial reductions in yield. The application of herbicides is widely recognized as the most effective strategy to address and reduce weed infestations [24].

3.1.6 Pigeon pea (Cajanus cajan L.)

Pigeon pea (Cajanus cajan L.) holds considerable significance within the realm of pulse crops. Globally, pigeon pea ranks fifth among grain legume crops [25]. Weeds are a major biotic factor that severely hampers pigeon pea yield, potentially leading to seed yield losses of up to 80 percent. The crop’s slow initial growth has been associated with significant weed infestations, leading to suboptimal crop development and yield. Consequently, effective weed management becomes a crucial factor in elevating the productivity of pigeon pea [26].

3.1.7 Cowpea (Vigna unguiculate L.)

Cowpea (Vigna unguiculate L.) stands as the foremost leguminous crop cultivated as pulse. Due to its slow initial growth, effective weed control becomes imperative during the early stages of crop development. The critical phase of competition between crop and weeds in cowpea occurs between 20 and 30 days after sowing (DAS). Prolonged competition throughout the season leads to significant yield reductions ranging from 40 to 90% in cowpea, depending upon various factors such as weed intensity, weed species, season, location, and prevailing climatic conditions. Different cultural methods, including mulching, manual weeding, and stale seedbed, can be employed for weed control in cowpea. However, the chemical method of weed control emerges as the most economical and viable option for managing weeds in cowpea [27].

3.1.8 Kidney beans (Phaseolus vulgaris L.)

The kidney bean or common bean (Phaseolus vulgaris L.) named for its resemblance to a human kidney holds immense nutritional value and is a vital pulse crop cultivated throughout the year. Numerous field experiments have shown substantial yield losses in common bean, ranging from 60 to 80%, when weed control is delayed after the emergence of the crop [28]. To tackle weed invasions, manual weeding is commonly employed. However, due to a shortage of labor during crucial periods and the increased wages of laborers, farmers seek more convenient and cost-effective alternatives. An integrated weed management approach, which combines low-dose herbicide application with manual weeding, is preferable. This not only ensures effective weed control but is also environmentally favorable [29].

3.1.9 Garden pea (Pisum sativum L.)

Peas (Pisum sativum L.) belong to the legume family, holding significance in both human and animal nutrition. Garden peas have been a dietary staple for millennia, offering a rich source of protein based on their utilization and consumption patterns [30]. Weed management becomes crucial seeing that field peas exhibit weaker competition with weeds compared to certain other species. The impact of weeds can result in yield losses ranging from 40 to 70% in garden pea cultivation. In situations with weed challenges, implementing integrated practices such as increased seeding rates and selecting appropriate cultivars can enhance the competitive edge of field peas, particularly in organic production [31].

4. Herbicides-a mid-20th century breakthrough

Herbicides, also known as weed killers, anti-weed agents, or weed eliminators, are effective chemicals employed for the control of unwanted plants in agriculture, contributing to enhanced crop production. Herbicides had a deep-rooted history dating back to ancient agricultural practices, where natural products like salt and olive oil were used. The mid-20th century witnessed a significant milestone with the introduction of synthetically manufactured herbicides. Sinox (Sodium dinitrocresylate), the first major organic chemical herbicide, emerged in France in 1896. In the late 1940s, new herbicides, stemming from research during World War II, marked the beginning of the “miracle” weed killer era. Within two decades, over 100 new chemicals were synthesized, developed, and deployed. The intensification of production, characterized by increased fertilizer usage, monocultures, and the cultivation of shorter crop varieties, commenced in the 1960s, resulting in heightened agricultural yields. Nevertheless, this also created favorable conditions for weed proliferation [32]. Since 1990, the global application of herbicides to agricultural land has experienced a surge of more than 260%, currently surpassing an annual quantity of 3 million tons [33].

Herbicides exhibit diverse classifications, which owing to the chemicals they contain, application methods, site of action, and timing of application. The mode of action for herbicides is a systematic, step-by-step process associated with herbicide treatment. Each herbicide’s mode of action is linked to a specific target site, often referred to as a mechanism of action [34]. Here are some of the classification outlining various types of herbicides [35]:

1. Specificity-based Classification:

   • Selective Herbicides

   • Non-Selective Herbicides

2. Method based on Application:

   • Soil-Applied Herbicides

   • Foliar-Applied Herbicides

3. Time of Application:

   • Pre-Plant Herbicides

   • Pre-Emergence Herbicides

   • Post-Emergence Herbicides

The process of herbicide application involves several distinct stages in its mode of action. Initially, the herbicide is applied, making direct contact with the plant. After application, the herbicide is absorbed by the plant. As the herbicide permeates the plant’s body, it moves to various plant areas, creating toxicity that ultimately results in the plant’s demise. Herbicides entering plants or weeds undergo metabolic changes influenced by compound properties, plant chemical composition, and the plant’s metabolic capacity. Tolerant plants can deactivate herbicides. Herbicides are commonly classified into different groups, each with specific modes of action [36].

• Group 1, ACCase inhibitors hinder lipid formation in roots and growing points and are primarily used post-emergence against grasses.

• Group 2, ALS/AHAS inhibitors disrupt amino acid synthesis, leading to plant death, and are applied post-emergence.

• Group 3, Microtubule assembly inhibitors impede cell division in plant parts and are applied pre-germination.

• Group 4, Synthetic auxins disturb cell growth in developing stems and leaves, applied to actively growing plants.

• Group 5, Photosynthetic inhibitors at Photosystem II Site A obstruct photosynthesis, used pre/post-emergence.

• Group 7, Photosynthetic inhibitors at Photosystem II Site B also hinder photosynthesis at a different site.

• Group 9, EPSP synthesis inhibitors block amino acid synthesis via the shikimate pathway, with broad-spectrum effects.

• Group 10 contains glutamine synthesis (GS) inhibitors, acting nonspecifically on nitrogen metabolism, leading to the accumulation of ammonia and disrupting cell functions and metabolic processes.

• Group 15 consists of cell growth and division inhibitors, applied through soil or foliar methods.

• Group 22, Cell membrane disruptors or PPO inhibitors target the cell membrane, disrupting its structure, and can be applied both pre and post the plant’s growth stage.

• Groups 12, 13, and 27 collectively known as pigment synthesis inhibitors, specifically target carotenoids, earning them the name carotenoid synthesis inhibitors. These herbicides also damage chlorophyll structure, giving rise to their colloquial name, bleachers, as they eliminate the natural green color of plants and render them white.

Nonetheless, the prolonged application of herbicides with the same pattern can lead to the emergence of herbicide-resistant weed ecotypes resulting in higher dosage of herbicides application [37].

4.1 Herbicide resistance in weeds

Herbicides play a crucial role in weed control, offering a time and labor-saving solution that significantly contributes to global food production. Despite their efficiency in managing weeds, the persistent use of herbicides is heightened concern across the world by the reason of the development of herbicide resistance in numerous weed species while crops bear a high susceptibility to herbicidal impact. Phytotoxic symptoms induced by herbicides in plants are characterized by leaf and shoot abnormalities, root and shoot stunting, the formation of leaf spots, chlorosis (yellowing of leaves), and necrosis (death of leaves). Moreover, herbicides can lead to oxidative damage, growth inhibition, interference with water and nutrient uptake, and disruption of the photosynthesis process [38]. Therefore, there is a significant demand for the advancement of crops that display resistance to herbicides. Data from the International Herbicide-Resistant Weed Database reveals a substantial increase in the evolution of weed species since the first documented case of herbicide resistance for triazines in 1970 [39]. Over time, the total number of herbicide-resistant weed species has increased dramatically, with developing resistance to 21 out of 31 known herbicide action sites and 165 different herbicides. Presently, herbicide resistance has been observed in 96 crops across 72 countries, with a global total of 513 reported cases involving 267 weed species [40]. Brosnan et al. documented the development of resistance in common turfgrass weeds like annual bluegrass and goosegrass to PSII-inhibiting herbicides and dinitroaniline herbicides [41]. Ghanizadeh et al. suggested that Chenopodium album may have developed resistance due to significant selective pressure from repeated applications of triazines in consecutive maize crops. Additionally, subsequent investigations uncovered the presence of dicamba-resistant C. album in maize fields. Solanum nigrum, a problematic weed in numerous pea and sweet corn fields and Persicaria maculosa, also exhibited resistance to triazines. Stellaria media displayed resistance to acetolactate synthase (ALS)-inhibitor herbicides. More recently, a population of Lolium perenne was identified as resistant to multiple ALS-inhibitors. ACCase-inhibitor resistance was observed in populations of both Avena fatua and Lolium multiflorum [42]. Heap et al. documented that Lolium rigidum retains its status as the most problematic herbicide-resistant weed globally, with Amaranthus palmeri, Conyza canadensis, Avena fatua, Amaranthus tuberculatus, and Echinochloa crus-galli following closely behind [43].

This trend emphasizes the need for sustainable approaches to weed management in agriculture. Herbicide resistance in agriculture is closely linked to the practice of intensive monoculturing, where various crops are commercially produced. Specific active ingredients within herbicides show a heightened occurrence of resistant weed species globally, particularly associated with monoculture farming systems. For example, Atrazine, which inhibits photosynthesis at photosystem II, has shown resistance in 66 different weed species across different crops. Glyphosate, an inhibitor of EPSP synthase, is now resistant for 57 different weed species, including pulses like chickpea, lentil, peas, and beans. Additionally, inhibitors of acetolactate synthase such as Tribenuron-methyl, Imazethapyr, Imazamox, Metsulfuron-methyl, Chlorsulfuron, Iodosulfuron-methyl-sodium, Bensulfuron-methyl, Thifensulfuron-methyl, and Mesosulfuron-methyl are no longer effective for controlling 45, 44, 40, 39, 38, 38, 29, 29, and 26 different weed species in various cash crops, including cereals and pulses. Moreover, the herbicide class Fenoxaprop-P-ethyl, acting as an inhibitor of fat synthesis and acetyl coA carboxylase, faces resistance in 33 different weed species. Paraquat and Simazine, known for reducing photosynthetic activity at photosystem I and II, respectively, encounter resistance in 31 different weed species. The synthetic auxin 2–4-D, also recognized as a plant cell growth disruptor, has developed resistance in 25 weed species (Figure 4) [44].

Figure 4.

Top 10 herbicides and the corresponding number of resistant species they are linked to [15].

4.2 Impact of herbicide application on crops

As previously discussed, over time, various weeds have developed resistance to different formulations of herbicides. Consequently, while weeds have rapidly evolved to resist chemical herbicides, our crops have fallen behind, resulting in a continual decline in yields. In pulses, the prevailing method for weed control typically consists of applying pendimethalin as pre-emergent (PRE) weedicide followed by manual weeding. However, this strategy falls short in managing subsequent weed flushes occurring approximately 1 month after sowing. As a result, post-emergence (POST) herbicides become necessary, yet there is not a specific herbicide recommended, especially for controlling broad-leaved species. Consequently, farmers turn to various commercially available herbicides for post-emergence application, which not only eradicate weeds but also impact desired plants [45]. To address this challenge, researchers are focusing on developing herbicide tolerance in pulse crops. It became necessary to manipulate the genetic composition of crops, which could be achieved through either recombinant DNA technology or mutation. Recombinant DNA technology was first utilized by Cole in 1994. Nowadays, the tobacco plant serves as a model plant for studying and optimizing the performance of alien genes. However, this technique has not proven to be significantly beneficial, as it involves various socioenvironmental risks and genetically modified plants themselves may not be safe. Careful management is required, which may be unsatisfactory [46]. In such circumstances, only mutation can introduce diverse genetic variations needed to achieve our objectives.

5. Development of herbicide-resistant crop via mutagenesis

In the light of the fact that the herbicides have long been the preferred method for effectively managing weeds and increasing crop productivity; however, the challenge lies in selectively eliminating weeds while ensuring the ultimate protection of desired plants. The development of herbicide resistance has become a desirable trait, particularly in various commercial crops. Thanks to the advancement in biotechnology, genetic engineering is predominantly employed, involving the selective mutations or the insertion of foreign genes making it possible to create herbicide-tolerant crops (HTCs) that mitigate significant yield losses. Over the past few decades, numerous genes have been identified that confer herbicide tolerance in valuable crops. This tolerance can result from mutations in native genes or the introduction of foreign genes to generate transgenic plants. Currently, various research initiatives and findings actively focused on the development of herbicide-resistant crops, with induced mutation emerging as a prominently highlighted method. Mutagenesis has emerged as a well-established technique in plant breeding, serving to complement available germplasm and enhance cultivars in specific traits. It effectively boosts genetic variability for crop improvement [47]. There are primarily three types of mutagenesis employed in mutation breeding:

• Induced Mutagenesis: This involves the use of radiations such as X-rays, gamma rays, or ion beams, as well as chemical mutagen treatments to induce mutations.

• Site-Directed Mutagenesis: This method is employed to deliberately create specific mutations at targeted sites within a DNA molecule. It is predominantly conducted through PCR-based techniques, including traditional PCR and inverse PCR.

• Insertion Mutagenesis: This process involves the creation of mutations through DNA insertion. This can occur through genetic alteration and t-DNA insertion or by activating a transposable agent [48].

Mutagenic agents such as radiation and specific chemicals are utilized to induce mutations. Physical mutagens, such as gamma rays, and chemical mutagens like ethyl methanesulfonate (EMS), ethyl nitrosourea, N-nitroso-N methyl urea, and sodium azide play a crucial role in this process.

5.1 Physical agents

Ionizing physical mutagens like gamma rays, x-rays, neutrons, and high-energy ions produce reactive free radicals that interact with DNA, causing chromosome deletions, rearrangements, and base loss, altering the structure and function of proteins and thereby modifying phenotypes. Gamma rays, particularly noted for their deep penetration, are extensively utilized. Plant breeders have generated valuable mutants of both Kabuli and Desi cultivars of chickpea using gamma rays and FN irradiation, respectively (Table 3) [49].

Ionizing agent	Merit	Demerit	Citations
Gamma Rays (γ)	Higher energy and deep penetration in plant tissue	Cannot create mutation in specific location of the genome and time consuming	[50]
Ultraviolet Rays (UV)	Strong genotoxic effect	Low penetration power and time consuming	[51, 52]
Fast Neutrons (FN)	Delete multiple gene at same time	Target site in the genome is not specified	[53]

Table 3.

Various ionizing agents and their respective merits and demerits.

5.2 Chemical agents

Chemical mutagenesis represents a basic and reliable approach for generating mutations. Agents like sodium azide, 1-methyl-1-nitrosourea (MNU), and diethyl sulfate have the capacity to induce mutations, with plant breeders predominantly favoring alkylating agents for this purpose [54]. This method often leads to a high frequency of nucleotide substitutions, with the majority (70–99%) of alterations in EMS-mutated populations involving transitions from GC to AT base pairs. Additionally, combinations of sodium azide (Az) and methylnitrosourea (MNU) are utilized, capable of inducing shifts in either direction, from GC to AT or from AT to GC. The dosage of a chemical mutagen primarily hinges on factors such as concentration, treatment duration, and treatment temperature. Various modifying factors, including pre-soaking, solution pH, metallic ions, carrier agents, post-washing, post-drying, and seed storage, also play significant roles. It is important to note that all these chemical mutagens are highly carcinogenic, necessitating extreme caution during handling and disposal [55].

5.3 Origin and history of mutagenesis

The origins of mutation induction can be traced back to around 300 BC in China, where early accounts of mutant crops emerged. However, significant advancements have been made over time to increase the frequency of mutations from ancient times to the present day. During the 1950s, 1960s, 1970s, and 1980s, activities related to mutation induction reached their peak, resulting in notable achievements such as the release of various mutant varieties. Numerous countries, such as China, India, Pakistan, Bangladesh, Vietnam, Thailand, Italy, Sweden, the United States, Canada, and Japan, have extensively utilized induced mutagenesis and mutation breeding to develop superior mutant varieties across a diverse array of important agricultural crop species. These include cereals, pulses, oilseeds, vegetables, fruits, fibers, and ornamentals [47]. Imidazolinone resistance is commonly developed in plants using mutagenesis, and these tolerant varieties, particularly those resistant to imidazolinones, have become frequently reported. The first commercialized HTC emerged in 1996, and currently, over 87.5 million hectares of land worldwide are planted with herbicide-tolerant crop varieties, constituting more than 45% of the total land area dedicated to mutant crop varieties. Various HTCs have been developed and commercialized against different herbicides. Examples include soybean, wheat, sunflower, and rice developed against ALS inhibitors, branded as Clearfield by BASF. Notably, these varieties are non-transgenic and are cultivated globally [56, 57]. Registered mutants are classified into different groups based on their enhanced characteristics or traits. These categories encompass agronomic traits (49%), quality traits (20%), yield or yield-related parameters (18%), biotic challenges (9%), and abiotic stresses (4%) [58].

5.4 Seed mutagenesis

Seed mutagenesis is primarily employed in sexually propagated plants, with seeds being the most frequently used plant material for inducing mutations due to their remarkable tolerance to harsh physical conditions (abiotic/biotic). While treating seeds, the dose that inhibits approximately 50% germination (LD50), is typically employed to achieve favorable outcomes. However, both the dosage and application duration of a mutagen vary depending on the plant species and must be determined through experimental investigation [59]. The protocol spans 3 days and comprises three main steps [60]:

1. Soaking seeds in water beforehand

2. Preparing the EMS solution and conducting mutagenesis and

3. Eliminating EMS, washing the seeds with a deactivating solution and water, and then proceeding to plant them.

Efforts have been underway for an extended period to cultivate imidazolinones/sulfonylureas-resistant crops through seed mutagenesis, demonstrating success in crops such as soybean, sunflower, wheat, corn, lentil, and canola. These crops are classified as non-transgenic because their tolerance/resistance has been achieved through the application of physical and chemical mutagens. Seed mutagenesis, widely employed in the selection process, has been crucial in developing herbicide resistance or tolerance in plants. These mutagenic agents are not limited to seeds but are also applicable to pollen. Among chemical mutagens, EMS has proven to be highly effective. Additionally, gamma radiation has been employed in seed mutagenesis, irradiating two lentil cultivars at doses of 90, 100, and 110 Gray to confer plant tolerance/resistance against chlorsulfuron herbicide. For plants with limited or absent seed production, mutagenesis can be applied to tissues (Figure 5) [61].

Figure 5.

Re-sprouting of chickpea mutant resistant to roundup.

5.5 Achievements of mutation breeding

The mutant varieties have shown improvements across diverse traits, encompassing increased yield, accelerated maturity, enhanced quality, and greater resilience to both biotic and abiotic stresses. Mutation breeding, unlike conventional methods, offers a potent means to introduce variability and facilitates the selection and genetic enhancement of pulse crops with limited genetic diversity. Globally, a total of 331 pulse crop varieties have been released through mutation breeding, with India leading the count with 122 varieties (excluding legumes like soybean and groundnut). Among pulse crops in India, the highest number of mutant varieties has been released for mung bean (34), followed by black gram (18), cowpea (16), chickpea (12), pigeon pea (12), moth bean (11), Lablab (6), lentils (4), horse gram (6), peas (2), and common bean (1) [62]. Induced mutagenesis, alongside related breeding strategies, possesses the capacity to enhance both quantitative and qualitative attributes in crops within a significantly shorter timeframe compared to traditional breeding methods. The widespread adoption of mutation breeding-derived agricultural varieties worldwide underscores its potential as a versatile and efficient approach applicable to various crops [63]. Various researchers have been independently focusing on different pulse crops, aiming to induce resistance against herbicides through mutation such as.

Singh et al. conducted a study on the sensitivity of lentil (Lens culinaris L.) to post-emergence herbicides, highlighting the need for the development of herbicide-tolerant cultivars. In the absence of natural variability, they employed mutation breeding as a powerful tool to introduce variability for desired traits in lentil. Specifically, 1000 seeds of the lentil genotype (LL1203) were subjected to gamma radiation (300 Gy, ⁶⁰Co) with the aim of inducing herbicide tolerance. Seeds of persisting M1 plants were individually harvested and divided into two parts to generate the M2 population, which was then subjected to herbicide application using imazethapyr and metribuzin. Data were collected for herbicide-tolerant M2 plants, including pod characteristics and yield per plant. The findings of the study indicated that metribuzin-tolerant mutants exhibited additional desirable traits, suggesting their potential utility in lentil breeding [64].

As per Toker et al., chickpea (Cicer arietinum L.) encounters an unresolved issue of sensitivity to various herbicides, including imidazolinone (IMI). In an effort to address this challenge, they employed induced mutagenesis to select for resistance to IMI across multiple Cicer species. The seeds were irradiated with gamma rays at doses of 200, 300, and 400 Gy from a 60Co source. Several dominant mutants were identified in the M1 generation, and these were subjected to a progeny test in the M2 generation. In the field application, the recommended dose of IMI was increased tenfold, and through this process, a highly IMI-resistant mutant of C. reticulatum was isolated [65].

Rizwan et al. provided a summary indicating that the lentil crop (Lens culinaris L.) exhibits a high sensitivity to herbicides, prompting a study aimed growing of herbicide-resistant mutants through chemical-induced seed mutagenesis. Three advanced genotypes were subjected to treatment with varying concentrations of ethyl methanesulfonate (0.1 and 0.2%), hydrazine hydrate (0.02 and 0.03%), and sodium azide (0.01 and 0.02%). The newly developed M2 population was assessed for resistance against two different herbicides, Ally Max and Atlantis. Across all environments, a total of 671 resistant mutants were identified. Recognizing the significance of these herbicide-resistant mutants, it is recommended that further evaluation be conducted at higher doses under controlled environmental conditions. The study could be advanced until the release of a new commercial herbicide-tolerant lentil cultivar [66].

In 2021, Galili et al. demonstrated that imidazolinone herbicides manifest a broad spectrum of weed control, yet chickpea plants display sensitivity to acetohydroxyacid synthase (AHAS, also known as acetolactate synthase [ALS]) inhibitors. Through the utilization of the chemical mutagen ethyl methanesulfonate (EMS), a chickpea line (M2033) was generated, displaying resistance to imidazolinone herbicides [67].

Hamid et al. also made significant contributions to their study by screening and assessing the tolerance of 145 mutagenized lentil genotypes at the M5 generation to imazamox herbicide. This included the evaluation of 139 M5 lentil genotypes derived from seeds mutagenized with ethyl methane sulfonate (EMS). Among these, five genotypes demonstrated notable tolerance to the herbicide [68].

5.6 Current advancements in induced mutagenesis

Previously, traditional methods of induced mutation played a crucial role in enhancing the resistance of crops to herbicides, but they were laborious and time-consuming. With the advent of transgenic techniques over the past few decades, significant progress has been made in crop improvement, leading to a substantial increase in transgenic herbicide-resistant crops. Genome editing by the modification of target DNA sequences through various methods such as addition, substitution, or selection of nucleotides emerging as a prominent method complementing mutation breeding efforts. This is achieved through technologies including zinc-finger nucleases (ZFNs), transcriptional activator-like effector nucleases (TALENs), base editors, clustered regularly interspaced short palindromic repeats associated with the Cas9 system (CRISPR/Cas9), and Primer Editors. These tools offer robust capabilities to enhance crop resilience against diverse challenges. Among them, CRISPR/Cas9 technologies are widely recognized as the most efficient and versatile genome editing tools [69]. Researchers have engineered herbicide-tolerant wheat crops by employing zinc-finger nucleases (ZFNs) after target the TaALS gene. Likewise, herbicide-tolerant rice and potato varieties have been developed through the use of TALENs, targeting the OsALS1 and SlALS1 genes, respectively [70].

The discovery of CRISPR/Cas genetic editing tools in 2012 paved the way for significant biotechnological and genomic advancements, enabling the rapid breeding of plants with desired traits such as increased yield, nutritional value, stress tolerance, and resistance to pests and herbicides. Numerous crop varieties, such as rice, maize, soybean, Arabidopsis, tobacco, cassava, flax, potato, and rapeseed [70], have been transformed as herbicide-resistant through the utilization of the CRISPR/Cas system. Despite its simplicity, flexibility, and high specificity, challenges remain in fully realizing the potential of CRISPR/Cas-mediated genome editing for crop improvement. Although progress has been made in creating herbicide-resistant crop germplasms, success has been primarily observed in resistance to specific types of herbicides, such as ALS-inhibiting and ACCase-inhibiting herbicides, as well as glyphosate. However, challenges persist in effectively controlling weeds resistant to other types of herbicides, such as 4-hydroxyphenylpyruvate dioxygenase and protoporphyrinogen oxidase inhibitors. Furthermore, while non-selective herbicides like glyphosate and glufosinate have broad-spectrum herbicidal properties, research on enhancing crop resistance to these herbicides is limited. Efforts in herbicide-resistant crop development primarily concentrate on selective herbicides, and there is a need for research into breeding crops resistant to multiple herbicides simultaneously. Thus, the development of non-selective herbicides or multiple herbicide-resistant crops remains an important focus [71].

These techniques have not yet been applied to develop herbicide-resistant pulse crops, indicating the need for its implementation in pulse crop breeding. While certain herbicide-resistant traits have been successfully introduced using this technology, further research is needed to address remaining challenges, particularly regarding the development of crops resistant to a broader range of herbicides.

6. Systemic approaches for chemical-free weed management

The adoption of agricultural methods such as organic farming or regenerative farming, which prioritize mechanical and cultural weed control measures over herbicide use, is on the rise. Therefore, successful weed management does not solely depend on the utilization of herbicides. Several methods are available for weed control that excluding the use of herbicides [32]. These include practices such as

1. Soil solarization

2. The stale seedbed technique

3. Crop establishment methods

4. Adjusting the crop planting date

5. Modifying crop density

6. Managing fertilizers

7. Incorporating cover crops

8. Intercropping

9. Mulching

10. Crop diversification.

Soil solarization, an environmentally friendly technique, has demonstrated effectiveness against various annual weeds, including annual bluegrass, Ageratum spp., Amaranthus spp., barnyard grass, cogongrass, common purslane, Digitaria spp., Portulaca spp., redroot pigweed, Setaria spp., and others. The stale seedbed technique proves successful against weed species with seeds primarily located in the topsoil, those with low initial dormancy, and seeds dependent on light for germination. Weed species susceptible to this technique include Cyperus iria, Digitaria ciliaris, Eclipta prostrata, Leptochloa chinensis, and Ludwigia hyssopifolia. The bed planting technique resulted in a 12.5% reduction in the population of Phalaris minor compared to flat sowing. Additionally, crop geometry, such as row spacing and planting patterns, significantly influences the competition between crops and weeds. Narrow row spacing, like 15 cm, led to a 16.5% reduction in Phalaris minor biomass compared to the standard spacing of 22.5 cm. Intercropping provides numerous advantages to a farming system. In an experiment, maize + blackgram (1:1) intercropping demonstrated lower total weed density and weed dry weight compared to other intercropping systems. Combining maize + blackgram intercropping with the application of pendimethalin at 0.75 kg per hectare, applied pre-emergence 3 days after sowing (DAS) and one-hand weeding 25 DAS, resulted in higher weed control efficiency. Including pulses as an intercrop in jute cultivation effectively suppressed dicot and sedge weeds by up to 54%. Mulches serve as effective tools for weed control. Increasing the mulch rate to 5.0 or 7.5 tons per hectare resulted in a reduction in weed biomass for various species. It reduced the emergence of grass, broadleaf, and sedge species by varying percentages. For instance, Phalaris minor, Oxalis corniculata, Medicago sativa, and Setaria glauca showed reduced biomass by 26–46%, 17–55%, 22–43%, and 26–40%, respectively [72].

6.1 Recently developed practices in weed management

6.1.1 Laser technique

In addition to conventional methods, advanced technologies such as laser weeding are now being implemented. A novel approach involves treating weeds using multiple laser beams without causing harm to non-target plants. Laser treatment effectively eliminates weeds by employing a high-energy laser beam that can either cut, burn, or release sufficient energy to inhibit their growth. The success of laser weed treatment is contingent upon factors such as wavelength, laser power, exposure time, and spot size. Currently, this method is being applied to carrots, cauliflower, and broccoli with sub-millimeter precision, enabling the elimination of up to 200,000 weeds/h. Experimental trials involving lasers have been conducted on common chickweed, scentless mayweed, and oilseed rape, demonstrating varying levels of susceptibility. Notably, certain species, such as B. napus, exhibit lower sensitivity to laser treatment and necessitate higher doses for effective weed control [73]. Although promising developments have been made with carbon dioxide laser radiation, these techniques are still in the experimental phase [74].

6.1.2 Thermal application

Utilizing thermic approaches has proven effective in rapidly managing weeds through various methods such as fire, flaming, hot water, steam, and freezing. Flaming, a commonly employed technique utilizing propane gas burners or renewable alternatives like hydrogen, achieves combustion temperatures of up to 1900°C [75]. This process leads to the destruction of plant membranes, causing a loss of cell function and ultimately resulting in the death or severe weakening of the plants. Flaming is particularly effective in controlling erect and broad-leaved weeds during their early growth stages, while its efficiency is relatively lower in managing grassy and prostrate weeds [76].

6.1.3 Robotics

Revolutionary agricultural robots are making their way into the market, with 22% specifically tailored for weed control. In the autonomous weeding domain, these robotic systems employ diverse methods for plant destruction, including cultivation, crushing, spot-spraying, electric shocks, lasers, and high-intensity light [77]. These systems incorporate computer vision techniques to identify and eliminate weeds in agricultural fields. Controlled effortlessly through a mobile app, this user-friendly robot is detailed by the authors, exploring its hardware and software components, encompassing cameras, motors, and microcontrollers. Field tests assessing the robot’s performance yielded results indicating a success rate of over 90% in detecting and removing weeds but farmers not widely embrace this technique [78]. Presently, this approach is being implemented on carrots and sugar beets, resulting in a weed control rate of 93.86% [73].

6.1.4 Unmanned aerials vehicles (UAVs)

UAVs represents an efficient and environmentally friendly approach to site-specific weed management. This technology allows for precise and continuous monitoring and mapping of weed infestations, achieved through the integration of UAVs with GPS technologies and advanced cameras and sensors capable of identifying specific weeds. Renowned for its excellent control capabilities in the presence of obstacles, this technique boasts advantages such as no soil compaction and minimal labor requirements [79].

6.1.5 Hyperspectral imaging sensors (HIS)

Hyperspectral imaging sensors have proven successful in detecting and distinguishing weeds, showcasing their effectiveness in agricultural applications. Hyperspectral imaging is commonly used for classifying agricultural systems and vegetation, being the most powerful and, currently, the sole method capable of robust and automated discrimination of individual plant species in the field [80]. In a study by Zhang et al., a hyperspectral imaging system was developed and coupled with a micro-spray heated oil application system for weed control in early-growth tomatoes. The authors reported that this approach accurately identified tomatoes, black nightshade, and pigweed at rates of 95, 94, and 99%, respectively. Importantly, this method remains robust even in the presence of visual occlusion of the leaf margin [81].

7. Conclusion

Weed infestation stands out a significant biotic factor contributing to a decline in global pulses production. Traditionally, herbicides have been used to mitigate or eliminate the impact of this interference. Selection pressure from herbicides has led to the emergence of herbicide-resistant weeds. Owing to this, herbicide exhibits dual effect as it not only eliminate weeds but also harm pulse crops. Therefore, the primary objective of plant breeding programs is to develop herbicide-resistant pulse crops with superior qualities. Induced mutation emerges as a highly efficient tool, widely utilized for quality improvement. Using physical or chemical mutagens, pulse crops can acquire resistance to herbicides. Consequently, this technique has found successful application in cereals, oilseeds, pulses, vegetables, and other crops. Seed mutagenesis is deemed an easy and cost-effective approach, and it requires substantial effort and time to produce desired crops. EMS, a chemical mutagen, is proving to be the most efficient choice for seed mutagenesis. Moreover, mutation breeding accompanied with modern technologies that help to identify the mutated alleles, leading to the development of successful mutants. This, in turn, helps to understand the gene function and enhance crop traits. New breeding technologies (NBTs) like genome editing enable targeted mutations in crop genomes, potentially increasing the transformation of herbicide tolerant crops. However, these methods have not yet been implemented in pulses. Therefore, researchers should consider integrating modern techniques alongside mutation breeding to develop herbicide-resistant pulse crops. In addition to induced mutation, researchers are also exploring alternative, precise, and chemical-free options such as thermal application, laser techniques, robotics, UVAs, and HIS for weed control in pulses.