Postharvest diseases/pathosystem of leguminous vegetable crops.
Vegetable crops have an important role in food and nutrition and maintain the health of soil. India is the second-largest producer of vegetables in the world with a 16% (191.77 MT) share of global vegetable production. Every year, diseases cause postharvest losses (40–60%) in vegetable crops due to their perishable nature under field (15–20%), packaging and storage (15–20%), and transport (30–40%). Profiling, detection, and diagnosis of postharvest vegetable pathogens (diseases) are essential for better understanding of pathogen and formulation of safe management of postharvest spoilage of vegetables. The vegetable produce is spoiled by postharvest pathogens and makes them unfit for human consumption and market due to the production of mycotoxins and other potential human health risks. Genera of fungal pathogens viz. Alternaria, Aschochyta, Colletotrichum, Didymella, Phoma, Phytophthora, Pythium, Rhizoctonia, Sclerotinia, Sclerotium, and bacterial pathogens viz. Erwinia spp., Pseudomonas spp., Ralstonia solanacearum, Xanthomonas euvesictoria were recorded as postharvest pathogens on vegetable crops. Fruit rot incidence of several post-harvest pathogens viz. Alternaria solani (30%), Phytophthora infestans (15%), Rhophitulus solani (30%), Sclerotium rolfsii (30%) fruit rot and X. euvesictoria (5%) canker on tomato; Colletotrichum dematium fruit rot (20%) on chili; Phomopsis vexans (60%) fruit rot on brinjal was recorded. Didymella black rot and Colletotrichum anthracnose were recorded on fruits of bottle gourd, pumpkin, ash gourd, and watermelon. Important leguminous vegetable crops are infected by postharvest pathogens viz. Ascochyta pisi, Colletotrichum lindemuthianum (Anthracnose), Sclerotinia sclerotiorum (white rot) and Pseudomonas syringae pv. phaseolicola (blight), Sclerotinia white rot, Alternaria blight. However, Xanthomonas black rot (10%) on cabbage and Pectinovora (Erwinia) soft rot (19%) were recorded as emerging post-harvest pathogens on cauliflower.
- vegetable diseases
- plant pathogens
- diseases management
- soil-borne diseases
India is the second-largest producer of vegetables in the world after China, and shares about 16% of global vegetable production . Processed vegetables have been exported at a compounded annual growth rate in the volume of 16% and in value of 25% [2, 3]. Vegetables have a significant role in enhancing farm income, sustainable global food as well as nutritional security. Vegetables suffer from several fungal and bacterial postharvest diseases [4, 5, 6]. Postharvest losses in vegetables are reported up to 30–40% owing to poor postharvest practices .
Fungicide is commonly applied for post-harvest disease control. Hot air, curing and hot-water brushing reduces disease incidence and increases the efficacy of antagonists. Biocontrol agents and botanicals may also reduce the amount of fungicide frequently used in postharvest disease management. Biocontrol of postharvest diseases of vegetable crops has great potential under storage conditions and biological products/biopesticides are available in the market. The biopesticides Ecogen US (Aspire™), Azotobactor (Bio-Save™), and Anchor (Yield Plus™) are involved to combine products with a low level of fungicide and salt solutions (calcium chloride or sodium bicarbonate @ 1–2%) and other food additives to improve efficacy against postharvest diseases. EcoSMART formulation based on rosemary oil, viz. EcoTrol™, Sporan™ (fungicide) and eugenol oil formulation Mataran™ (weedicides) are recognized as safe plant protectants. Therefore, the postharvest application of eco-friendly control methods may be exploited to manage the disease of vegetables.
2. Economical and health impact of postharvest diseases of vegetables
Postharvest diseases cause qualitative and quantitative losses of vegetables and make them unfit for human consumption due to potential health risks. A large number of postharvest diseases are caused by black, white, and yellow fungi-derived carcinogenic mycotoxins and mutagenic secondary metabolites . Losses due to postharvest disease may occur during the handling of produce from harvest to consumption. Primary and secondary agricultural practices are also important and costs such as harvesting, packaging, and transport must be taken into account when estimating the value of the produce lost as a result of postharvest wastage. Fresh vegetables are highly perishable, and they have relatively short shelf lives. Fresh vegetables are living, respiring tissues that start senescing immediately after harvest. They are mostly comprised of water, with most having 90–95% moisture content. Because of the perishable nature of vegetables, special skills are required for postharvest handling.
3. Challenges of postharvest losses in vegetable crops
Application of good postharvest management practices which are supported by good technologies and also improving postharvest systems will maintain the quality of vegetables and reduce quantitative losses. Losses in vegetables are the result of (i) poor knowledge about the right harvesting index; thus, a large proportion of the harvested beans are usually over-mature (ii) poor handling practices, such as the use of plastic sacks for bulk packaging and transportation which results in mechanical damage that serves as entry points for disease-causing organisms leading to rotting of the pods (iii) poor transport practices such as the use of trucks that have no cover, thus exposing the produce to direct sunlight and high temperature (iv) the absence of low-temperature storage facilities and transport systems, and (v) rough handling practices during distribution in retail markets.
4. Causes of postharvest diseases
In general, postharvest diseases and losses of vegetables are incited by fungi and bacteria. Postharvest diseases are often classified on the basis of the infection as “quiescent”or “latent”, where the pathogen infects before harvest in the field. Examples of postharvest diseases arising from quiescent infections include anthracnose of various vegetables caused by
5. Detection of postharvest pathogens
Pathogens were isolated on agar medium and identified on the basis of macroscopic and microscopic analysis of colony and conidia/spore morphology by Microscopy, Sero-diagnostics (ELISA, Dot-blot assays), and nucleic acid (PCR) based methods.
Why do we need, want, or should detect emerging postharvest pathogens (diseases) in vegetable crops?
Determine presence and quantity of the pathogen (s) for quarantine legislation.
Assess the effectiveness of Integrated Disease Management (IDM) modules.
Issuing of Sanitary and Phytosanitary (SPS) certificate vegetable produce for safe export/transboundary movement under trade.
Quantify spatial and temporal pathogen populations in a specific location.
Quantify pathogen populations in relation with regional and seasonal yield losses.
6. Postharvest fungal diseases
Common postharvest diseases resulting from wound infections initiated during and after harvest includes blue and green mold (
White mold (
|Watery soft rot or white stem rot||Disease symptom initially appears in the form of water-soaked lesions on pods and stems. Later, infected tissues become whitish and covered with white mycelia mats and black-colored sclerotia.|
|Anthracnose||Disease symptoms appear in the form of brown to black sunken spots and lesions on leaves, stems, and pods. The center of anthracnose lesions on pods is covered with numerous black dot-like acervuli.|
|Black spot symptoms on pods result in the production of round tan-colored sunken spots bearing dark margins with pycnidia on pods.|
|Charcoal rot or ashy stem blight||Disease symptoms appear in the form of dark brown to black charcoal-colored lesions covered with black dot-like fruiting bodies (resting microsclerotia and pycnidia) on pods.|
|Sclerotiorum rot||Whitish growth with mustard-like sclerotia on pods.|
|Cottony leak||White mycelial growth on pods.|
Phytophthora: late blight
Colletotrichum: fruit rot
Gummy stem blight (GSB) is caused by
|Colletotrichum fruit rot||Chili||20|
7. Postharvest bacterial diseases
Phytopathogenic bacteria cause postharvest diseases of economically important vegetables. Different species of bacteria belonging to top ten genera viz.
Biological (culture media, diagnostic hosts, bacteriophages (phage typing); biochemical (based on properties of the bacteria in culture (gram stain, bacterial cell size, flagella), metabolic fingerprinting (API/BIOLOG system), thin layer chromatography, gel electrophoresis, conductance assays, isozyme analysis); immunoassays (agglutination, gel diffusion, ELISA, dot blot assays, immunofluorescence, flow cytometry); nucleic acid (hybridization, RFLPs, PCR, ICAN, DNA arrays, multilocus sequence typing) were used for reliable and accurate detection of plant pathogens for their effective management.
The disease is caused by pathogen,
Pectobacterium: soft rot
|Summer squash||Soft rot||5–10|
8. Postharvest disease management
Postharvest losses in vegetables are found due to fungal and bacterial infection worldwide. New challenges are faced under trade liberalization and globalization, and serious efforts are needed to reduce these losses in vegetables.
8.1 Chemical control
Chemical fungicides are commonly used for the management of postharvest disease in vegetables. For postharvest pathogens which infect produce before harvest, the fungicides should be applied at field level during the crop season, and/or strategically applied as systemic fungicides. At the postharvest level, the fungicides are often applied to reduce infections already established in the surface tissues of produce or they may protect against infections occurring during storage and handling. Fungicides used during postharvest are actually fungistatic rather than fungicidal under normal usage. The fungicides are applied on the produce as dips, sprays, fumigants, treated wraps, and box liners or in waxes and coatings. Dip and spray methods are very common in postharvest treatments. The fungicides generally applied as a dip or spray method are benzimidazoles (e.g. benomyl and thiabendazole) against anthracnose, and triazoles (e.g. prochloraz and imazalil) and fumigants, such as sulfur dioxide, for the control of gray mold used for postharvest disease control [24, 25]. Dipping in hot water (at 50°C for 5–10 min, depending on the size of produce in combination with the fungicide) is also used for effective control of the disease. Sodium hypochlorite as a disinfectant is used to kill spores of pathogens present on the surface of the vegetable produce.
8.2 Biological control
International markets reject produce containing unauthorized pesticides, with pesticide residues exceeding permissible limits, and with inadequate labeling and packaging. Hence, biological control of postharvest diseases has great potential because postharvest environmental conditions like temperature and humidity can be strictly controlled to suit the needs of the biocontrol agent. Much information has been provided in relation to postharvest biocontrol and the problems faced by the development of commercial products [26, 27]. Biological control is used through microbes such as fungi, bacteria, actinomycetes, and viruses (bacteriophages) to control the postharvest disease of vegetables [1, 28, 29, 30, 31]. The degree of disease control or disease suppression achieved with these bioagents can be comparable to that achieved with chemicals. As per estimates, the market of Indian bioagents is equivalent to 2.89% of the overall pesticide market in India with the worth of rupees 690 crores. It is expected to show an annual growth rate of about 2.3% in the coming years [32, 33]. In India, so far only 18 types of bio-pesticides have been registered under the Insecticide Act of 1968. Among agriculturally important microbes,
Antagonistic yeast forms a biofilm to stick pathogen and parasitize on the hyphae of the pathogen. Bar-Shimon et al.  reported that biocontrol efficacy of yeast correlates with the production of lytic enzymes and their ability to tolerate high concentrations of salts. Further, molecular approaches were used to examine the role of glucanases in the biocontrol activity of the yeast
An effort has been made to develop two new products based on yeast antagonist
8.3 Plant essential oils
Botanical pesticides cause no adverse effects on non-target biota with biodegradability. It should be noted that most of the crops sprayed with botanical pesticides are quite safe for consumption after a short period after spraying. A large number of defensive of rich chemicals such as terpenoids, alkaloids, phenols, tannins, coumarins, flavonoids, etc. are present in plants which cause physiological effects on pathogens. These compounds have already been identified in the extracts/exudates of many plants. They have antimicrobial activities and are used for postharvest disease control.
The use of natural botanical products would be a supplement or an alternative to synthetic fungicide. Examples include 1,8-cineole, the major constituent of oils from rosemary (
Many exhaustive studies have been carried out on the utility of neem oil against various fungal pathogens. Its efficacy has been evaluated against fungal pathogens and found to be on par with the fungicide hymexazole in the control of the soil pathogens
9. Postharvest handling operations of vegetable crops
Maintenance of hygiene in all stages of postharvest handling is critical to minimize the source of primary inoculum for postharvest diseases . Produce should be harvested during the day instead of early morning. Field containers should be smoothed. Containers should be cleaned. Sterilized packing and grading equipment, particularly brushes and rollers, are used. Chlorinated water @ 100 ppm is commonly used for washing vegetables. This can be done with chlorine gas or with either liquid hypochlorite (pH 6.0–7.0). Containers should not be overfilled, which causes severe damage during stacking. Management of temperature is the most important factor to extend the shelf life of fresh vegetables after harvest. It begins with rapid removal of the field heat by using any of the following cooling methods: hydro-cooling, in-package ice, top icing, evaporative cooling, room cooling, forced air cooling, serpentine forced air cooling, vacuum cooling, and hydro-vacuum cooling. The relative humidity during storage should be maintained at about 85–95% for most fruits and 95–98% for vegetables. Transport vehicles should always be cleaned and sanitized before loading.
For postharvest disease management, various strategies such as postharvest handling systems, sanitation, and integration of botanicals/plant essential oil, microbial bioagents, and safe chemicals need to be integrated and develop integrated postharvest diseases management techniques under World Trade Organization (WTO) regime. Among them, it is expected that the knowledge of biocontrol will lead to new, innovative approaches to minimize postharvest decay of the product and it presents the best hope for the future of postharvest disease management of vegetable produce. Future research in this field will include a better understanding of the molecular basis of variability in the pathogen, pathogenesis, accurate and reliable diagnostic of the disease and to engineer novel and durable protection strategies against devastating postharvest diseases of vegetable crops.
Tripathi AN, Meena BR, Pandey KK, Singh J. Microbial bioagents in agriculture: Current status and prospects. In: Rakshit A, Singh HB, Kumar Singh A, Singh US, Fraceto L, editors. New Frontiers in Stress Management for Durable Agriculture. 1st ed. Singapore: Springer Nature; 2020. pp. 490-499. 361-368
Chikkasubbanna V. India (2). In: Rolle RS, editor. Postharvest Management of Fruit and Vegetables in the Asia-Pacific Region. Tokyo: Asian Productivity Organization; 2006. pp. 143-151
Choudhury ML. Recent development in reducing postharvest losses in the Asia-Pacific region. In: Rolle RS, editor. Postharvest Management of Fruit and Vegetables in the Asia-Pacific Region. Tokyo: Asian Productivity Organization; 2006. pp. 15-22
Tripathi AN. Detection and diagnosis of emerging postharvest pathogens (diseases) in vegetable crops. Book of Souvenir and abstracts. In: Bashyal BM, Das A, Kumar A, Kamil D, Hussain T, Geat N, Devappa V, et al, editors. International e-Conference on Postharvest Disease Management and Value Addition of Horticultural Crops. August 18-20, 2021. New Delhi, India: Division of Plant Pathology ICAR-IARI; 2021. p. 7
Tripathi AN. Emerging diseases and their management in vegetable crops. In: Webinar on Applied Microbiology and Beneficial Microbes. August 26-27, 2021. Greenville, USA: Coalesce Research Group; 2021. p. 8
Tripathi AN, Singh D, Pandey KK, Singh J. Postharvest diseases of leguminous vegetable crops and their management. In: Singh D, Sharma RR, Devappa V, Kamil D, editors. Post-Harvest Handling and Diseases of Horticulture Produce. 1st ed. London: CRC Press; 2021. pp. 387-396
Ahsan H. India (1). In: Rolle RS, editor. Post-Harvest Management of Fruit and Vegetables in the Asia-Pacific Region. Tokyo: Asian Productivity Organization; 2006. pp. 131-142
Klich MA. Aspergillus flavus: The major producer of aflatoxin. Molecular Plant Pathology. 2007; 8:713-722
Hedayati MT, Pasqualotto AC, Warn PA, Bowyer P, Denning DW. Aspergillus flavus: Human pathogen, allergen and mycotoxin producer. Microbiology. 2007; 153:1677-1692
Tripathi AN, Sharma P, Agarwal PC, Usha D, Hazarika BN, Tripathi SK, et al. Aflatoxins: Threat for agricultural trade and food safety. In: Prasad D, Ray DP, editors. Biotechnological Approaches in Crop Protection. New Delhi, India: Biotech Books; 2013. pp. 490-499
Tripathi AN, De RK, Sharma HK, Karmakar PG. Emerging threat of Sclerotinia sclerotiorum causing white/cottony stem rot of mesta in India. New Disease Reports. 2015; 32:19
Tripathi AN, Sarkar SK, Sharma HK, Karmakar PG. Stem rot of roselle: A major limitation for seed production. Jaf News. 2013; 11:14
Tripathi AN, Sarkar SK, Sharma HK, Karmakar PG. Detection and characterization of roselle stem rot pathogen, Sclerotinia sclerotiorum(Lib.) de Bary and its sensitivity towards bioagents. In: National Symposium on Plant Pathology in Genomic Era. Chhattisgarh, India: Department of Plant Pathology, Indira Gandhi Krishi Vishwavidyalay, Raipur; 2014. pp. 8-9
Bolton MD, Thomma BPHJ, Nelson BD. Sclerotinia sclerotiorum(Lib.) de Bary: Biology and molecular traits of a cosmopolitan pathogen. Molecular Plant Pathology. 2006; 7:1-16. DOI: 10.1111/j.1364-3703.2005.00316.x
Tripathi AN, Pandey KK, Meena BR, Rai AB, Singh B. An emerging threat of Phytophthora infestanscausing late blight of tomato in Uttar Pradesh, India. New Disease Reports. 2017; 35:14
Tripathi AN, Pandey KK, Rai AB, Sunil G. Late blight: An emerging disease of tomato in eastern Uttar Pradesh. Vegetable News Letter. 2016; 3(1):4-5
Drenth A, Sendall B. Practical guide to detection and identification of Phytophthora. CRC for Tropical Plant Protection Brisbane. Version 1.0. 2001. pp. 20-27
Mansfield J, Genin S, Magori S, Citovsky V, Sriariyanum M, Ronald P, et al. Top 10 plant pathogenic bacteria in molecular plant pathology. Molecular Plant Pathology. 2012; 13(6):614-629. DOI: 10.1111/J.1364-3703.2012.00804.X
Strange NR, Scott PR. Plant disease: A threat to global food security. Annual Review of Phytopathology. 2005; 43:83-116. DOI: 10.1146/annurev.phyto.43.113004.133839
Tripathi AN. Bacterial diseases of vegetable crops and their management. In: Pandey KK, Rai AB, Singh B, editors. Recent Advances in Integrated Management of Pest and Disease in Vegetable Crops. ICAR-IIVR Training Manual No. 81. 2018. pp. 70-82
Vauterin L, Rademaker J, Swings J. Synopsis on the taxonomy of the genus Xanthomonas. Phytopathology. 2000; 7:677-682
Young JM, Park DC, Shearman HM, Fargier E. A multilocus sequence analysis of the genus Xanthomonas. Systematic and Applied Microbiology. 2008; 5:366-377
Toth IK, Kenneth SB, Holevia MC, Birch PRJ. Soft rot erwiniae: From genes to genomes. Molecular Plant Pathology. 2003; 4(1):17-30
Ampatzidis Y, DeBellisL LA. Pathology: Robotic applications and management of plants and pant diseases. Sustainability. 2017; 9(6):1010. DOI: 10.3390/su906 1010
Waard D, Georgopoulos MA, Hollomon SG, Ishii DW, Leroux P. Chemical control of plant diseases: Problems and prospects. Annual Review of Phytopathology. 1993; 31:403-421
Droby S, Cohen L, Wiess B, Daus A, Wisniewski M. Microbial control of postharvest diseases of fruits and vegetables—Current status and future outlook. Acta Horticulturae. 2001; 553:371-376
Droby S, Wilson C, Wisniewski M, ElGhaouth A. Biologically based technology for the control of postharvest diseases of fruits and vegetables. In: Wilson C, Droby S, editors. Microbial Food Contamination. Boca Raton, FL: CRC Press; 2000. pp. 187-206
Chaurasia A, Meena BR, Tripathi AN, Pande KK, Rai AB, Singh B. Actinomycetes: An unexplored microorganisms for plant growth promotion and biocontrol in vegetable crops. World Journal of Microbiology and Biotechnology. 2018; 34(9):132
Loganathan M, Rai AB, Pandey KK, Nagendran K, Tripathi AN, Singh B. PGPR Bacillus subtilisfor multifaceted benefits in vegetables. Indian Horticulture. 2016; 61(1):36-37
Mohamed B, Benali S. The talc formulation of Streptomycesantagonist against Mycosphaerellafoot rot in pea ( PisumsativumL.) seedlings. Archives of Phytopathology and Plant Protection. 2010; 43:438-445
Pandey KK, Nagendran K, Tripathi AN, Manjunath M, Rai AB, Singh B. Integrated disease management in vegetable crops. Indian Horticulture. 2016; 61(1):66-68
Cheng XL, Liu CJ, Yao JW. The current status, development trend and strategy of the bio-pesticide industry in China. Hubei Agricultural Sciences. 2010; 49:2287-2290
Thakore Y. The biopesticide market for global agricultural use. Industrial Biotechnology. 2006; 2006:194-208
Bar-Shimon M, Yehuda H, Cohen L, Weiss B, Kobeshnikov A, Daus A, et al. Characterization of extracellular lytic enzymes produced by the yeast biocontrol agent Candida oleophila. Current Genetics. 2004; 45:140-148
Droby S, Cohen L, Daus A, Weiss B, Horev E, Chalutz E, et al. Commercial testing of Aspire: Abiocontrol preparation for the control of postharvest decay of citrus. Biological Control. 1998; 12:97-101
Droby S, Wisniewski M, El-Ghaouth A, Wilson C. Influence of food additives on the control of postharvest rots of apple and peach and efficacy of the yeast-based biocontrol product Aspire™. Postharvest Biology and Technology. 2003; 27:127-135
Droby S, Wisniewski M, El Ghaouth A, Wilson CL. Biological control of postharvest diseases of fruits and vegetables: Current advances and future challenges. Acta Horticulturae. 2003; 628:703-713
Tripathi AN, Gotyal BS, Sharma PK, Tripathi RK, Usha D, Biswas C, et al. Essential oils: As a green biopesticide for organic farming. In: Biswas SK, Pal S, editors. Organic Farming and Management of Biotic Stresses. New Delhi, India: Biotech Books; 2014. pp. 548-554
Toth IK, van der Wolf JM, Saddler G, Lojkowska E, Helias V, Pirhonen M, et al. Dickeya species: An emerging problem for potato production in Europe. Plant Pathology. 2011; 60:385-399