Plant Diseases of Areca Nut

Abstract

Areca nut has source of complex carbohydrates and natural fiber for humans. Almost all parts of this plant can be utilized. This plant is a commodity with high economic value in Indonesia. Moreover, the daily consumption of areca nut is passed down from generation to generation, a tradition is known as ‘chew Pinang’. The seeds of this plant are always present in the completeness of several traditional events in Indonesia. The development of this plant encountered challenges such as decreased productivity levels due to infection with pathogenic microorganisms. Pathogens that attack areca nut commodities can be in the form of bacteria and fungi. Leaf midrib rot is caused by the mycelia of the pathogenic fungus Athelia rolfsii, in addition to infection with Penicillium sp. during plant growth also results in losses. Phytophthora arecae, Micoplasm-like Organism (MLO), Ganoderma lucidu, Colletotrichum gloeosporioides, Curvularia sp., Pestalotia palmarum Cooke., Cephaleuros sp., Ganoderma lucidum, Fusarium sp., Rhizoctonia sp., Xanthomonas campestris, Ceralostomelia paradox.

1. Introduction

Areca nut belongs to the category of straight trunked trees with a height of up to 30 meters and a diameter ranging from 25 to 40 meters. The average life span is up to 60 years and some species can reach 100 years. This plant is estimated to be native to Sulawesi (Celebes) Indonesia, Malaysia, and New Guinea [1]. It’s distribution covers the tropics in Asia, the Pacific, and parts of East Africa. Areca nut is known by the names beter palm nut, catechu, areca nut, and many other names. This plant can adapt to disturbed land, swamp forest edges, and creeks.

Almost all parts of this plant are economically viable for humans. Plant morphology Areca nut has pinnate leaves with a length of 1-1.5 meters. The base of the midrib leaf is gray and has a crown shape. Branched flower stalks reach a length of 1 meter and grow from under the crown stalk. The fruit has red or orange seeds with a length of 5-6 cm and a width of 4-5 cm. The shape of the fruit varies from round to slightly flat. Taxonomically, Pinang is included in the Spermatophyta division, Monocotyledone class, Order Arecales, Family Arecaceae, and Genus Areca [2].

Areca nut is known as a plant with benefits in every organ it has. These benefits include areas in human life and their role in the ecosystem. The presence of several bacterial phyla (Proteobacteria and Actinobacteria) in this plant’s rhizosphere is known to synergize to help maintain the balance of nutrient cycles in the soil around the roots, thereby maintaining overall betel nut health and increasing plant productivity. This is related to the production of growth hormone, the enzyme 1-Aminocyclopropane-1-Carboxylate (ACC) deaminase which triggers growth and activity against plant pathogens. On the other hand, the use of this plant tree as a yard and garden plant [3]. The stems of this traditional community in Indonesia are used as an important ingredient in the areca climbing competition on Indonesia’s independence day by every region in this country. The tradition of the fishing community throws betel leaves into the sea to invite fish to come. In the field of textile dye development, areca nut contributes as a natural dye for Sasirangan batik in South Kalimantan, Indonesia [4]. Areca nut is also reused as ornamental lighting commodities which have a selling value [5]. Young betel nut juice is commonly consumed by the public. Processed smoked betel nut becomes a light snack and is usually used as souvenirs typical of districts in Aceh, Indonesia. In addition, the cosmetic industry has also used betel nut powder as an additional ingredient in the production of transparent soap [6]. Its role in the ecosystem includes a part of agroforestry as an improvement in economic, ecological, and social systems [7]. This cultivation system makes it possible to grow seasonal crops together with crops that can be used in the livestock sector [8]. In addition, areca nut is used for erosion control (dune stabilization) and soil improvement [9].

Based on the description above, the productivity of this plant is very important to be maintained. Disease disturbance in plants is a problem that should be found a solution. Some of the symptoms of areca nut disease and matters that are closely related to the factors that cause the severity of the disease are discussed in this chapter.

2. Factor causing plant disease

Plant health can be a factor that supports plant productivity. A simple definition of a plant health disorder can mean an imbalance in the proportion of normal growth and development caused by biotic and abiotic agents. Abiotic factors such as temperature, humidity, gas atmosphere, and light intensity that provide access to the presence of plant pathogens, decrease productivity or cause plant death directly. Several factors above interact with each other in achieving a state of balance in achieving plant health. Abiotic agents that cause disease in this case are environmental stress conditions and their handling and cultivation. While the biotic agents in question are plant pathogenic infections, including bacteria, fungi, and viruses.

2.1 Abiotic factors

Season (rainy and hot in Indonesia), summer lasts a chance to make the roots dry out, morphologically the roots will shrivel and die. This condition is caused by not allowing the roots to function in absorbing water from the soil.

Low humidity increases evaporation in plants so that moisture stress can occur. When the water supply to the leaves is inadequate, the concentration of the hormone abscisic acid increases rapidly, causing the leaf stomata to close. This process is known to protect plants from excessive water loss. Low humidity in outdoor situations is not usually a problem. This condition is often temporary and rarely results in reports of serious damage. However, if this condition is combined with other factors and occurs at the same time then symptoms of plant disease can appear. These symptoms are temporary to permanent wilting of plants, burnt leaves, and shriveled/wrinkled fruit due to excessive loss of water content. High humidity allows evaporation to occur in plants, inhibiting nutrients from being absorbed by plants. Impaired absorption of nutrients can have an impact on cell formation disorders. For example, plants with young fruit skins are prone to cracking during periods of prolonged high humidity. This provides an opportunity for further pathogens to infect exposed fruit parts without skin dressing.

The temperature fluctuates, while plant physiological activities such as photosynthesis, respiration, membrane permeability, absorption of water and nutrients, transpiration, enzyme activity, and protein denaturation can be directly affected by temperature. The response of plants to the minimum, optimum and maximum temperatures can be different for each plant. Likewise in plants in different places in the same physiological process. In general, plants that grow at the upper and lower limits of the optimum range tend not to grow as well as plants that grow at the optimum temperature range. Sexual organs such as fruit and flowers will grow smaller than plants that grow at optimum temperatures.

The lowest temperatures can cause damage to plant tissue, the level of damage will be exacerbated by stable low temperatures for a long time. Low temperatures can damage the young meristem webs, damaging the tips of young roots. The leaves of the plant will appear yellow and fall. Plant cells can be damaged because low temperatures disrupt the stability of the cell membrane to damage the entire contents of the cell. From low temperatures to freezing points, ice can also damage cell membranes and other vital materials in plant cells. High temperatures can cause damage in the form of coagulation and denaturation of plant proteins, disruption of cell membranes, and secretion of toxins into cells, resulting in cell death. This is through a slowed-down protein synthesis process, the production of ‘heat shock proteins to defend the plant from damage. The severity depends on how high the temperature is and the length of exposure.

Wind speed factors affect the spread of plant diseases caused by fungi. This is related to the carrier and spread of conidium and the ability to stick to the plant surface. Light intensity affects several things such as exudation, sporulation, and the dispersion and growth of fungal conidium in the soil. Basically, with adequate light intensity, plant diseases can spread quickly, especially plant diseases caused by fungi. This is supported by related research explaining that conidium Cercospora in tobacco can spread and cause picking disease [10]. It also includes environmental imbalances such as air pollution (ozone, hydrogen fluoride, sulfur dioxide, ethylene, and peroxyacetyl nitrate).

2.2 Biotic factors

Pathogenic infections such as bacteria, fungi, and viral pathogens can cause the severity of symptoms that appear and play an important role in the spread of areca nut disease. An explanation of these biotic factors will be discussed in the next section.

2.2.1 Plant disease symptoms

We often observe sick plants in the field. To facilitate sample collection activities, field observation methods are needed. The methods used in field observations on symptoms of plant disease include:

1. Absolute method, observation of plant disease symptoms was carried out thoroughly by the population in the field. The resulting data will represent population estimates in numbers and individuals per unit of the land surface.

2. Relative method, in this condition, the observer will determine a sample of the existing population by considering the sample taken represents the actual conditions in the population. Observing plant disease symptoms in this way will be more difficult to represent the condition of land surface unit conversion.

3. Population index method, observers only measure the indicated part of the attack, it can be a symptom of an attack, and the results obtained are the extent of the attack.

If in the field they have found a method to observe plant disease symptoms, of course, the next step is researchers must be skilled in determining plant disease assessment techniques, here are some things that need to be considered:

1. severity,

2. describe and compare the symptoms and severity of the disease,

3. scoring of symptoms,

4. calculate the attack rate or disease index.

The description below will describe some of the diseases in Pinang caused by.

microorganisms in the tropics and subtropics:

2.2.1.1 Symptoms of fruit rot in areca nut

This disease is caused by the fungus Phytophthora arecae. This incident began with symptoms of rot and the fall of young fruit from the base of the tree. Symptoms begin with the discharge of dark green/yellowish liquid on the fruit near the petals. The damage spreads to cover the entire surface of the fruit, causing rot. The surface of the fruit is covered with a white mycelium sheath followed by the condition of the fruit stalk rotting and/or dry and not infrequently also covered with white mycelium (Figure 1).

Figure 1.

Fruit rot on the areca nut [11].

2.2.1.2 Symptoms of yellow leaf in areca nut

This disease was discovered as an investment of a Micoplasm-like Organism (MLO) attack. Symptoms are marked by yellowing of the leaf tips and as many as 2-3 strands of branching. Signs of necrosis in the form of brown parallel lines on the leaves, then yellowing extends along the leaf blade and the tips of the leaves dry up. At an advanced stage, the leaves turn yellow and fall off the stem. Symptoms can also be observed at the tips of the roots which gradually turn black. This infection in mature leaves causes the functional leaf cross-sectional area for photosynthesis to decrease (Figure 2).

Figure 2.

Symptoms of yellow leaf disease [11].

2.2.1.3 Symptoms of foot rot in areca nut

This disease is caused by infection with the fungus Ganoderma lucidum. The leaves turn yellow and eventually fall. The stem becomes brittle due to strong winds, and the color of the base of the stem shows a change to brown and secretes a dark liquid. Mushroom hood-shaped fruit grows at the base of the stem, changes in color at the roots and the condition of the roots is drier than before. When the infected stem is cut longitudinally, a brown discoloration can be seen along one meter of the height of the stem from the ground (Figure 3).

Figure 3.

(a) the hood of Ganoderma lucidum grows at the base of the stem, (b) disease symptoms on the canopy tree [12].

2.2.1.4 Symptom of bud rot in areca nut

This disease is caused by the fungus Phytophthora arecae. Early symptoms that can be observed are leaf changes from green to yellow to brown. The leaves and shoots that appear rot and one by one the leaves fall from the stem (Figure 4).

Figure 4.

(A-B) symptoms of leaf color change to yellow then brown, (C) colony morphology Phytoptora arecae on agar media, (D) conidia of P. arecae [11].

2.2.1.5 Symptoms disease of inflorescence die back in areca nut

This disease is caused by a fungal infection Colletotrichum gloeosporioides. Symptoms appear as brownish spots and spread from the tip to the bottom of the inflorescence and cause wilting of the male flowers. Conidia appear as concentric circles in areas of discoloration (Figure 5).

Figure 5.

(a) Brown spots that appear as a symptom disease, (b) wilting as a disease investment [13].

2.2.1.6 Symptoms disease of band in areca nut

Symptoms can be observed in the shape of the leaves that are shortened and resemble the shape of a broom, it is not uncommon to find some signs of discoloration to pale wilting and/or yellowish or dark green spots appear. In addition, changes in the shape of the tree crown such as the shape of a rose, shorten the distance between the trunk segments.

2.2.1.7 Symptoms of yellow spot disease in areca nut

These symptoms appear due to the attack of the fungus Curvularia sp. Several symptoms can be observed on the leaves including yellowish spots on the leaf blade, yellow and green spots, the size of the leaves becomes shorter and shaped like a broom, and sometimes the color of the leaves becomes pale, yellow, and drooping. Leaf tips become brown or yellow (Figure 6).

Figure 6.

(A-B) symptoms of leaf spot disease, (C) colony morphology of Curvularia sp., (D) Conidia Curvularia sp. [11].

2.2.1.8 Symptoms disease of leaf blight in areca nut

This disease is caused by the fungus Pestalotia palmarum Cooke. The symptoms of this disease show yellowish spots on the leaf blade, the color of the leaves becomes pale, the tips of the leaves become pale and wilted, and the leaves are shortened and shaped like a broom (Figure 7).

Figure 7.

Symptoms of leaf blight on areca nut: (A) symptoms of brown spot on leaves, (B) colony morphology of Pestalotia palmarum Cooke., (C) conidia of P. palmarum [11].

2.2.1.9 Symptoms disease of red rust in areca nut

Areca red rust disease is caused by infection with the fungus Cephaleuros sp. This disease is characterized by symptoms of yellowish spots, the crown of the leaves withers suddenly, the leaf stalk changes its color to yellowish and the leaf midrib leaves only stick (Figure 8).

Figure 8.

Symptoms of red rust disease on areca nut: (A-B) symptoms of rust spots red on leaves, (C) sign of hyphae growth on leaves, (D) microscopic morphology of Cephaleuros sp. [11].

2.2.1.10 Symptoms disease of root rot in areca nut

This disease is caused by several pathogenic microbes. Some of them are Ganoderma lucidum mushrooms. In addition, fungi Fusarium sp., and Rhizoctonia sp. It also plays an important role in the severity of disease symptoms. Symptoms of this disease show yellowish-brown discoloration and root rot while the plant stem tissue secretes a dark brown liquid. The leaves shorten and resemble a broom (Figure 9).

Figure 9.

Symptoms of root rot disease on areca nut; (A) infection of the base of the stem, (B) systemic symptoms on the tree, (C) fruiting bodies of Ganoderma lucidum, and (D) spores of G. lucidum [11].

2.2.1.11 Symptoms of shoot wilt in areca nut

The crown leaves wilt suddenly, the color of the leaves becomes dull, the tips of the leaves turn brown, and the leaf midrib hangs and finally falls.

2.2.1.12 Symptoms disease of bacterial leaf stripe in areca nut

The fungus Xanthomonas campestris Areca is known to be present in areca nut infections. Symptoms of the disease arise in the form of yellowish or dark green spots on the leaf blade, the underside of the leaf surface is covered by bacterial colonies, and yellowish leaf twigs, in the end, the leaf arrangement grows irregularly and is grayish white. The crown of the tree resembles a rose.

2.2.1.13 Symptoms disease of stem bleeding in areca nut

Symptoms of this disease can be observed in stems that change color to dark red, stem tissue secretes dark brown fluid, yellowish spots on leaf blades, roots turn yellowish brown and rot is not uncommon. Another symptom of the fruit shows a change in color to dark green. This disease is known to be caused by the fungus Thielaviopsis paradoxa. Von Hohn (Ceralostomelia paradox).

2.2.1.14 Symptoms disease of nut splitting in areca nut

Symptoms of the disease that can be observed from this condition include yellowish spots on the leaf blade, yellowish fruit color in the half-ripe fruit phase, and the apical end of the fruit showing signs of falling fruit.

2.2.1.15 Symptoms disease of Antracnose in areca nut

Symptoms that can be observed from this disease are brown circular spots with yellow circles surrounding the spots. The leaf veins turn yellow from the tip to the base of the leaf (Figure 10).

Figure 10.

Antracnose; (A-B) symptoms of brown spots on leaves with a yellow halo around them, (C) morphology of the fungus Colletotrichum gloeosporioides, (D) conidia of fungi C. gloeosporioides [11].

2.2.1.16 Symptoms disease of leaf sheath rot

Symptoms that can be observed in midrib rot disease are yellowish white and brown sclerotia on the leaves and covered with white mycelia on the surface. There are first reports of the attack of this disease by the fungus Athelia rolfsii in India [14].

3. Pathogen infection cycle and chain

The disease cycle is inseparable from a pathogenesis [15]. An infection cycle can occur over and over again during a plant’s growth period. If this condition continues repeatedly, it is referred to as a chain of infection, so that the pathogen spreads to fill the planting area. The sequence of disease occurrence and disease distribution includes the stages of spore germination, penetration, colonization, infection, sporulation, and disease dispersion. Biochemical processes begin to take place as long as the spores germinate. If the spores are active, if they get the right conditions (host plants and a supportive physical and chemical environment), infection will likely occur. Spores are referred to as dispersion units. Spores germinate morphologically visible germination tube, swelling of the germination tube is known as appressorium, and hyphae to attach when penetration occurs in the host plant tissue. This development becomes the unit of infection. Units of infection can cause disease symptoms [16]. In the areca nut itself, disease symptoms can occur in the vegetative organs and generative organs. Symptoms of the disease can be recognized locally or systemically. If the symptoms occur locally, they only occur in one organ, for example in the leaves. However, if the symptoms are systemic, some organs change, for example, stem bleeding is found in the cross-section of blackish brown fluid, yellowish spots on the leaves, and root rot due to a manifestation of systemic infection.

The chain of infection can be divided into homogeneous chains if the dispersion unit consists of only one type. For example, the dispersion unit is only conidia. However, in the case of an infection chain consisting of several dispersion units such as ascospores and conidiospores, it is said to be a heterogeneous infection chain. Very often this heterogeneous chain of infection occurs in different seasons in perennial plants [16].

4. Plant defense response

The defense response of plant cells against pathogenic microbial infections are divided into two mechanisms, including mechanisms related to 1) the structure of the plant body itself including the presence of a waxy layer on the surface of plant organs. On the other hand, hard and thick epidermal cells narrow the chance of pathogen penetration. In addition, plant defenses against pathogens are also found in the various structures of stomata and guard cells as natural access that plants have to pathogens. For many plant varieties with narrow entrance variations and tall and wide guard cells reduce the chances of pathogens penetrating; 2) production of antimicrobial secondary metabolites. This is a limiting factor for the continued penetration of pathogenic microbes [16].

When pathogens attack plant cells, plant enzymes catalyze oxidative reactions to produce reactive oxygen species that can damage pathogenic microbial cells. This reactive oxygen also serves to strengthen cell walls as well as signal intermediaries to neighboring cells that foreign cell attacks are taking place. In addition, plant cells respond by synthesizing and storing some callose (polysaccharide polymer) which is located between the cell wall and the plant cell membrane. Callose blocks the penetration of pathogenic cells at the site of infection [16].

5. Genetic variations of areca plants in Indonesia and resistance to pathogens

Diseases of areca nut attack the vegetative and generative organs. Vegetative organs that are the target of disease-causing pathogens include roots, stems, and leaves. Meanwhile, generative organs such as seeds, fruits, and flowers cannot be separated from the attack of pathogenic infections (Table 1).

No.	Accesion	Island Origin in Indonesia	References
1	Sumut-1, Sumbar-1, Sumbar-2,; Sumut-2, Bengkulu-1, Sumbar-3,; Bengkulu-2, Galang Suka (GSK), Tarean (TRN), Betara-1, Betara-2, Muara Sabak Timur-1, Muara Sabak Timur-2, Muara Sabak Timur-3, Wangi, lokal	Sumatra	[17, 18]
2	Molinow-1 (MLW-I), Molinow-2 (MLW-II), Mongkonai (MGK), Duhia Da’a, Tingkohubu I, Tingkohubu II, Huntu I, Huntu II, Huntu III, Bulawan	Sulawesi	[19]
3	Oyehe (OYH), Kali Harapan (KHN), Nifasi (NFS)	Papua	[20]
4	Saluang	Kalimantan	[21]

Table 1.

Areca nut varieties in Indonesia.

New varieties are obtained from studying genetic diversity. One way to determine the diversity of a betel nut species is based on differences in morphological characteristics (either qualitatively or quantitatively) which are directly related to fruit production. Genetic diversity can be obtained by crossing, introduction, mutation, and selection of genetic sources. Selection based on morphological characters is a method that is often done. The selection was made on the morphological characteristics of the areca nut that were directly related to fruit production, namely the number of bunches, the number of fruit marks, and the number of spikelets [22]. Some of the morphological characteristics of areca nut that are often observed in genetic diversity research include stem height, stem circumference, number of leaf marks, number of leaves, number of bunches, number of fruit per bunches, whole fruit weight, fruit polar length, fruit equatorial length, fruit kernel weight, kernel polar length and kernel equatorial length [23]. One of the Pinang varieties in Indonesia which is classified as a superior variety is Pinang Betara. This variety received a recommendation from the government in the Decree of the Minister of Agriculture No. 199/Kpts/SR.120/1/2013. The characteristics of Pinang Betara include 1) dry kernel production/tree/year 5.70 kg, stem height reaches 10 meters, has 131.35 fruit/bunch, whole fruit weight is 47.06 grams, dry seed weight is 8.68 grams, high 9.79% tannin, has a dry kernel potential of 7.81 tons/hectare (Figure 11) [24].

Figure 11.

Several varieties of areca nut in Indonesia, from Sumatra Island: (A) Pinang Wangi, (B) Pinang lokal [23], (C) Pinang Betara [22], from Sulawesi island: (D) Pinang Duhia Da’a-Gorontalo, Tingkohubu, Huntu I, Huntu II, Huntu III [19].

The incidence of root rot can be caused by plant genetic factors so that the resistance response of each plant variety can be different [25]. Different genetic factors between plant varieties are derived from different inherited genes. Each variety has a different resistance to S. rolfsii fungus attack. The resistance properties found in each of these varieties are coded for resistance genes to fight pathogens. In other words, the resistance control genes possessed by each variety are different [26]. The Character of resistance to Fusarium sp. wilt disease. Judged by several things: 1) disease period value (day after inoculation), 2) disease incidence (%) and 3) endurance category (units/day). According to this study, a longer incubation period correlates with lower disease incidence and slower infection rates [27].

6. Conclusion

Diseases in plants can be caused by an imbalance of environmental conditions, pathogens with high pathogenicity, and susceptible hosts. These three factors trigger disease severity in plants. This paper describes sixteen diseases in areca nut caused by the presence of pathogens, infection cycle and chain, plant defense response, as well as genetic variation affects plant resistance to pathogens.

Acknowledgments

The author would like to thank the head of the biology department, the Dean of the Faculty of Science and Technology, and The Rector of Universitas Islam Negeri Ar-Raniry Banda Aceh, Indonesia who has allowed the author to contribute to this chapter of the book.

Conflict of interest

The authors declare no conflict of interest.