Wilt diseases of tomato (Lycopersicum esculentum) and chilli (Capsium annum) and their management strategies: Emphasis on the strategies employed in Sri Lanka: A review

Wilt is one of the major diseases causing economic losses in many crops. It is caused by infections of many bacterial (Ralstonia solanacearum), fungal (Fusarium spp., Vertcillium spp., Rhizoctonia spp., Sclerotium spp.), oomycete (Pythium spp., Phytophthora spp.) and viral (Tomato spotted wilt virus) pathogens. This review provides an overview on the control strategies used in other countries for the wilt disease in highly susceptible vegetable/fruit crops; tomato and chilli and make comparisons with Sri Lanka. Many studies have been performed on the prevalence, severity, pathogenicity and the control of these infections in both crops worldwide. Wilt in tomato is caused mainly by Ralstonia solanacearum and Fusarium oxysporum and in chilli mainly by Fusarium oxysporum. Tomato bacterial wilt is successfully managed through usage of resistant cultivars, grafting, biological control agents, inducing host systemic resistance and integrated management. Tomato and chilli wilt caused by Fusarium sp. have been successfully controlled mainly through the application of chemicals and biological approaches such as systemic defense induction and the use of microbial antagonists. In Sri Lanka, tomato wilt is reported as being the result of bacterial, fungal and viral infections which have been mainly controlled by the usage of resistant cultivars, physical measures and cultural practices. Chilli wilt in Sri Lanka has not been thoroughly studied yet. But application of fungicides has been an effective strategy for fungal wilts. Wilt threat of tomato and chilli in Sri Lanka has to be further studied for the proper management of these infections and for freeing tomato and chilli cultivations from the wilt disease.


Significance of tomato and chilli
Tomato, used as a vegetable and chilli as a spice, owe a prominent place in a balanced diet. Tomato is a highly demanded, nutritive vegetable mainly in vegetarian diets throughout the world. It is also a good source of vitamins C and A and minerals such as Fe and Cu (Siemers, 1971). Tomato has a high demand as a fresh and as a processed product both in local and foreign markets.
Chilli plays a significant socio economic role worldwide due to its nutritional value, medicinal properties, industrial and ornamental properties. Chilli is in high demand as a good source of vitamins (A, B1, B2, B3, C and E), carotenoids and capsaicinoids. Tomato and chilli are two vital vegetable crops among Sri Lankan farmers due to its high economic returns and export potential.

Constraints for tomato and chilli production
Commercial tomato and chilli production is hampered worldwide due to many biotic and abiotic stresses. Tomato is primarily vulnerable to economic losses due to postharvest damage caused by its highly perishable nature, inefficient postharvest handling procedures and consequences of preharvest diseases. Tomato is infected by various phytopathogens. Almost all the parts of the tomato plant are susceptible to many pathogenic infections at various growth stages. Anthracnose, blossom end rot, sunscald, early and late blight, septoria leaf spot, fusarium wilt, bacterial wilt, verticillium wilt, damping off, southern blight, powdery mildew, gray leaf spot, tomato spotted wilt virus, tobacco mosaic virus are the most common tomato fruit crop diseases around the world. Among these, tomato wilt is the most destructive disease causing much damage to tomato cultivations.

Constraints
to commercial chilli production include both pre-harvest and postharvest damage caused by phytopathogens. Pre-harvest infections include wilt diseases, damping off, other fungal, bacterial and viral infections while the main postharvest damage of chilli is anthracnose caused by a fungal infection in addition to mechanical damage. Common pathogenic infections on chilli include anthracnose, bacterial leaf spot, bacterial soft rot, bacterial wilt, fusarium wilt, cercospora leaf spot, damping off, powdery mildew, verticillium wilt and various viral infections (Pea enation mosaic virus (PeMV), Tobacco etch virus (TEV), Tobacco mosaic virus (TMV)). Among them, wilt, damping off and anthracnose are the major diseases largely affecting commercial chilli production in Sri Lanka.

Wilt disease
Wilt is a plant disease that results from the infection of roots and vascular system of plants by several phytopathogenic fungi, bacteria, virus and nematodes. Infection of roots and vascular vessels hinder water transportation resulting in wilting of the stems and leaves. It was recorded that wilt is one of the major diseases causing the highest preharvest losses.
Bacterial wilt disease is mainly caused by several bacterial species belonging to the genera Pseudomonas, Corynebacterium, Erwinia and Xanthomonas. Wilt disease is also caused by fungal pathogens such as Fusarium, Pythium, Phytophthora, Rhizoctonia, Sclerotium and the species Verticillium dahlia. The infected crops suffer from stunting, wilting, withering, chlorosis, necrosis and defoliation of plant parts which finally results in the death of the plant. Wilt infections cause huge economic loses in many solanaceous crops such as tomato (Solanum lycopersicon), potato (Solanum tuberosum), chilli (Capsicum annuum), tobacco (Nicotiana sp.), brinjol (Solanum melongena), cucumber (Cucumis sativus) and in banana (Musa sp.) in tropical, subtropical and temperate regions (Hartman & Elphinstone, 1994).

Wilt infections in tomato
Tomato wilt is caused by several different phytopathogens. Wilt caused by Ralstonia solanacearum, Fusarium spp., Verticillium spp., Sclerotium spp. and Rhizoctonia spp. has been reported in tomato. Among them, bacterial wilt caused by Ralstonia solanacearum is identified as the greatest threat to tomato cultivations in Sri Lanka (Bandara, 1983;Ilankoon, 2001;Gunathilake et al., 2004).

Bacterial wilt in tomato
Bacterial wilt is known to occur mainly in the wet tropics, sub tropics and some warm temperate regions of the world such as China, Fiji, India, Indonesia, Papua New Guinea, Phillipines, Sri Lanka and Thailand (Persely, 1986). This can bring about the total destruction in tomato during rainy seasons. In Asia it is a serious infection in the lowland humid tropics and in the cooler tropical highlands, but not in the semi-arid tropics.
It is caused by the soil borne pathogen, Ralstonia solanacearum E.F.Smith, previously known as Pseudomonas solanacearum, a widespread pathogen of solanaceous hosts. The disease affects more than 200 plant species in over 35 -50 families throughout the world including a wide range of crop plants, ornamentals and weeds (Kelman, 1953;Hayward, 1995). The major economic hosts include potato, tomato, eggplant, pepper, ginger, peanut, banana etc.
The primary source of this causal agent is the soil. The infection occurs through wounds in the root system caused by mechanical damages or root knot nematodes and pores via emerging lateral roots. Once the pathogen enters the host, it invades the xylem of the plant and disrupts water translocation resulting rapid wilting and death. Disease symptoms are said to appear four days after the infection (Ilankoon et al., 2001).
Diseased plants release large number of bacteria to the soil resulting infection of neighboring plants. R. solanacearum is known to spread within and between countries by soil, water and through latently infected planting materials. The spread of this causal agent is facilitated by cultural practices such as furrow irrigation, transplanting, pruning, hydroponics etc. In addition, high soil moisture and optimum temperature for the pathogen also favour disease development and dispersal (Kranz et al., 1997).
Initial symptoms of bacterial wilt are visible on tomato foliage. The youngest leaves at the end of the branches wilt during the hottest part of the day. Gradually the entire plant may wilt and desiccate although dried leaves remain green, leading to general wilting and yellowing of foliage and eventually plant death. Another common symptom associated with this in the field is stunting of the plant. In addition, collapse of the stem may also be observed (Champoiseau & Momol, 2009) (Figure 1).

Tomato bacterial wilt disease in Sri Lanka
Even though bacterial wilt is one of the major obstacles in tomato production in Sri Lanka, there are only limited records on disease incidence, prevalence and remedies in Sri Lanka (Bandara, 1983;Bandara, 1984;Velupillai, 1986;Ilankoon et al., 2001;Gunathilake et al., 2004;Senarathna et al., 2012). These reports are on diversity, pathogenicity and biotype distribution of R. solanacearum and report grafting and varietal resistance as remedies for the disease. Park & Fernando, (1938) first reported the threat of bacterial wilt in tomato in the wet zone. A high incidence of bacterial wilt has been reported in Nuwara Eliya in 1986 in Sri Lanka (Vellupillai, 1986). The incidence of this disease is mainly reported from the mid and low country wet and intermediate zones in Sri Lanka as revealed by Kelaniyangoda, (1995). According to Abeygunawardana & Siriwardana (1961), bacterial wilt was a limiting factor for the extension of potato in elevations below 1540 m. It should be the same in case of tomato. Solanaceous crops such as chilli, eggplant, tomato and potato in Sri Lanka are susceptible to the bacterial wilt disease caused by R. solanacearum (Velupillai, 1986).
More detailed studies have been carried out on the bacterial wilt disease on potato in Sri Lanka (Velupillai, 1986), but not on tomato. In 1969, Senevirathne classified the bacterial wilt pathogen in Sri Lanka into three biovars using Hayward's (1964) biochemical classification. Gunawardana et al., (1980) (Gunawardana et al., 1980). Gunathilake et al., (2004), sixteen of the selected R. solanacearum isolates were highly virulent while four were moderately virulent on the susceptible tomato variety Marglobe. According to that report, the pathogen shows a high genetic diversity in the Kandy, Matale and Monaragala districts. It was further reported that the isolate collected from Hanguranketha (Maoya) can be used for screening of existing tomato germplasm in Sri Lanka for bacterial wilt resistance since it has recorded the highest relative pathogenicity score value. Bandara, (1983) studied the biotype distribution of the vascular wilt pathogen R. solanacearum in Sri Lanka. He detected the biotype 2 and 3 of R. solanacearum in Sri Lanka. Prior to that Senevirathne, (1969) had also reported the occurrence of the biotypes 2, 3 and 4 in the hill country of Sri Lanka. According to Bandara (1983), the biotype 3, isolated from samples collected from all over the island was pathogenic to all solanaceous crops. He further stated that the wet and dry climatic zones haven't apparently had any effect on the distribution of the biotypes of R. solanacearum. In addition, Bandara, (1983) reported that many samples of P. solanacearum collected from the hill country dry zone were found to carry Pseudomonas marginalis which had a synergistic effect on the wilt disease occurrence. P. marginalis showed similar biochemical reactions as the biotype 4 of P. solanacearum. This is a crucial finding in regard of wilt infections in Sri Lanka.

Management of tomato bacterial wilt
It was reported that the economic loss of tomato due to bacterial wilt is greater than any other crop (Hayward, 1995). Therefore, control of this disease is an essential prerequisite for a high profit targeted tomato cultivation. The causal agent of bacterial wilt, R. solanacearum, is a complex, heterogeneous species. Disease control has become difficult due to its wide host range, wide spread and vast genetic diversity of the pathogen (Hayward, 1991). Various control strategies including the induction of host resistance (Dalal et al., 1999;Hase et al., 2008), development of transgenic resistant varieties (Jia et al., 1999), adhering to appropriate cropping systems (Dalal et al., 1999), soil amendments (Vincent & Mew, 1998) and the practice of integrated control (Katayama & Kimura, 1987) and biological control (Guo et al., 2003) have been adopted in many cases (Table 1). Table 1 indicates control strategies employed for the management of bacterial wilt of tomato. Among them breeding for disease resistance has been a promising approach (Persely, 1986). Wang et al., (1998), evaluated thirty five tomato lines to form an international set of resistance sources to bacterial wilt infection.
Bacterial wilt resistant commercial varieties, breeding lines and wild tomato accessions were used in this study. Danesh et al., (1994), evaluated oligogenic resistance to tomato wilt through a cross between a resistant and a susceptible parent. The selection of bacterial wilt resistant tomato has also been attempted by Toyoda et al., (1989)  According to Oda, (1995), Lee, (1994) and Ilankoon, (2001), grafting of tomato varieties to disease resistant stocks has been successfully used as an effective control measure. The team specifically studied grafting as a successful remedy for the bacterial wilt disease. As revealed in a survey done in Japan in 1995, 45-66% of tomato cultivated in protected agricultural systems was grafted tomato plants (Oda, 1995). Ilankoon, (2001), reports that of the two locally recommended wilt resistant varieties, KWR is a better root stock than T 245 for obtaining wilt resistant seedlings of the Daniella hybrid, while both rootstocks can be used for the SS 100 hybrid in Sri Lanka.
Integrated tomato wilt management has been also attempted as a control measure for the wilt disease. Once Anith et al., Biological control of the bacterial wilt pathogen, R. solanacearum has also been attempted by many scientists. Vesiculararbuscular mycorrhizae (Halos & Zorilla, 1979), avirulent mutants of R. solanacearum (Dong et al., 1999), genetically engineered antagonistic bacteria (Kang et al., 1995) and some naturally occurring antagonistic rhizobacteria such as Bacillus spp. (Silveira, 1995), Pseudomonas spp. (Guo et al., 2001) and Streptomyces spp. (Albyad et al., 1996), plant growth promoting rhizobacteria (PGPR) (Guo et al., 2004)  In addition to these, the usage of soil less, single solid media has also been practiced as a remedy for this soil borne bacterial infection. Although much work has not been done on this strategy, it seems a strategy that could be applied widely. As reported previously, of these different control measures, biological control of R. solanacearum and usage of wilt resistant tomato cultivars have been the most promising.
Wilt caused by the fungus Fusarium oxysporum is also a common infection in tomato in many parts of the world in addition to the wilt infection caused by Verticillium albo-atrum.

Fusarium wilt in tomato
Fusarium wilt is another highly destructive disease found in commercial tomato cultivations grown under either green house or field conditions in many warm regions of the world. It is caused by a soil borne pathogen, Fusarium oxysporum f.sp. lycopersici. This infection is reported to cause 10-50% yield loss in tomato (Larkin & Fravel, 1998;Borerro et al., 2004).
The plants infected with Fusarium oxysporum suddenly show signs of wilting. Lower leaves turn yellow and start to die. Finally the whole plant wilts and dies within few days. The soil borne pathogen colonizes the vascular system of the plant, destroys the xylem vessels which transport water and nutrients and thereby causing the plant to wilt. These symptoms are somewhat similar to bacterial wilt symptoms.

Management of tomato Fusarium wilt
The proper management of the causal agent of fusarium wilt, the soil borne Fusarium oxysporum has not been successful as the fungus lives particularly in or near the dynamic environment of the rhizosphere and can frequently survive long periods in soil with the help of resistant structures. It has been recorded that the commonly applied control measures against this pathogen infection are pre plant fumigation and fungicide application (Larkin & Fravel, 1998). In addition, biological control (Srivastava et al., 2010;Haruna et al., 2012) and induction of host resistance (De Cal et al., 1997;Fuchs et al., 1997;Samia & Khalal, 2007) have also been tested and successfully used in controlling Fusarium wilt (Table 2).
Several different methods have been attempted to manage the Fusarium wilt disease. Induction of host resistance and biological control has been prominent among other approaches. The defense mechanisms of a tomato plant have been activated through the induction of the expression of β-fructosidase (Benhamou et al., 1991) by a combination of chitosan and endophytic bacterial strain (Benhamou et al., 1998), the application of Pseudomonas fluorescens and a nonpathogenic F. oxysporum (Duijff et al., 1998) and by applying three types of composts against the causal agent F. oxysporum (Fattah & Al-Amri, 2012 Nejad and Johnson, (2000) studied the suppression of the tomato wilt disease by endophytic bacteria isolated from roots and stems. Srivastava et al., (2010) also studied the biological control potential of fluorescent Pseudomonas, Trichoderma harzianum and Glomus intraradices an arbuscular myccorhizal fungus alone and as combinations. A fusaric acid resistant mutant of Pseudomonas solanacearum also has been successful in controlling the Fusarium wilt causal agent (Toyoda et al., 1988). Szczech, (1999), studied the potential of vermicompost in suppressing F. oxysporum.

Verticillium wilt in tomato
Tomato wilt is also caused by infection of soil borne pathogenic fungus Verticillium albo-atrum. This pathogenic fungus attacks the roots, travels up along the xylem vessels and blocks them. This hinders the normal flow of water and nutrients to the leaves. Older leaves become yellow or brown and stems tend to discolour. Eventually the plant dies. This infection is much favoured under cold weather and difficult to manage due to the ability of this fungus to persist in soil for a longer period. Crop rotation, well maintained field conditions and usage of resistant varieties have been successfully applied as control measures of this infection.
In addition, southern blight and walnut wilt diseases too cause wilting symptoms in tomato. But these infections are not prominent in causing economic losses in tomato. Therefore paying attention on minimizing these minor infections also would lead to healthy tomato cultivation and thereby gain a higher profit.

Tomato wilt diseases recorded in Sri Lanka
In Sri Lanka, tomato wilt is primarily caused by the bacterium R. solanacearum. Other types of wilt infections such as Verticillium wilt or southern blight infection of tomato are not reported from Sri Lanka. Detection of the incidence and possibility in infection of these two wilt threats is also worthwhile to ensure wilt free tomato cultivations. Although biological control and usage of resistant cultivars have been the most effective and widely studied control measures worldwide, biological control of bacterial wilt has not been applied in managing the bacterial wilt threat in Sri Lanka though some attempts have been made. However, the evaluation of resistant cultivars has been conducted to a satisfactory level. Induction of tomato host resistance is also a successful strategy studied by many scientists in managing tomato wilt. Unfortunately the use of this strategy has not been investigated in Sri Lanka. Identification of the biological approaches (biological control and host defense induction) in managing this significant infection would be also worthwhile with regard to sustainable agriculture.

Wilt infections in Chilli
Wilt is reported to be the most frequently encountered disease problem in chilli (Skaggs et al., 2000;Siddiqui & Akhtar, 2007). Wilting of chilli could be due to infections brought by bacteria, fungi, virus or nematodes. Fusarium wilt, bacterial wilt, phytopthora root rot, pythium root rot, verticillium wilt and rhizoctonia root rot are several different types of wilt diseases detected in chilli (Sanogo, 2003). Young chilli plants at a vegetative stage are more susceptible to wilting and infected plants show withering off of leaves, a dark streak developing upward from the collar region and ultimately plants die due to death of the xylem tissues ( Figure 2). In Southern New Mexico, 43% of the chili producers have reported wilt as the most frequently encountered disease problem in chilli (Skaggs et al., 2000). The annual income loss due to these wilt infections is reported to be between 20 -25% in Sri Lanka (Kelaniyangoda, 2011).

Fusarium wilt in chilli
It was reported that Fusarium oxysporum is the main causal organism for wilt in chilli. Wilt disease caused due to this fungal infection is common in chilli worldwide compared to the other wilt infections.
The pathogen infects young roots, grows, develops and spreads in root and stem vascular vessels inhibiting water and nutrient transportation (Miller et al., 1986). Therefore, the leaves of chilli plants first tend to wither and thereafter lead to the death of the whole plant. The characteristic symptoms of the disease are brown vascular discoloration followed by upward and inward rolling of the upper leaves and subsequently wilting of the plant (MacHardy & Beckman, 1981;Rivelli, 1989). The chilli yield loss due to this Fusarium wilt disease reportedly varies between 10 -80% worldwide (Loganathan et al., 2013). Several species of soil borne Fusarium are responsible for the wilt disease of chilli. F. oxysporum, F. solani, F. moniliforme and F. pallidoroseum have been reported as wilt causing agents of chilli. F. oxysporum and F. solani are the most prevalent species of Fusarium found associated with wilt of chilli in India (Naik, 2006).

Management of chilli Fusarium wilt
Several biological control approaches (usage of antagonistic microorganisms, botanicals, dairy components, essential oils, resistance inducers) and integrated management is one of the main strategies that has been adopted to manage the fusarium wilt in chilli (Table 3). Different antagonistic microorganisms such as chitinolytic bacteria (Suryanto et al., 2010), Trichoderma harzianum, T. viridae, T. aureiviride, Bacillus subtilis and Pseudomonas fluorescens (Ragab et al., 2012), T. koningii and T. aureoviridae (Sahi & Khalid, 2007) have been successfully applied in controlling the Fusarium spp. infection in chilli. Singh et al., (2017) evaluated twelve botanicals for their inhibitory activity against F. oxysporum inciting wilt disease in chilli while Shafique et al., (2015) and Suprapta & Khalimi, (2012) evaluated the antifungal effect of methanolic leaf extracts of Eucalyptus citriodora and 14 selected tropical plants in Bali island. Essential oils (Cinnamon, clove, thyme, lemon grass, lemon, mint, pepper mint, mustard) in suppressing fungal growth and chemical plant resistance inducers such as sodium benzoate, potassium bicarbonate, potassium sorbate and chitosan in induction of resistance against the wilt causal agent F. oxysporum were tested by Ragab et al., (2012). The possibility in usage of cow and buffalo dairy components in managing F. oxysporum infection has also been attempted by Maharaja et al., (2017).

Bacterial wilt in chilli
Bacterial wilt in chilli is also caused by the same pathogenic bacterium Ralstonia solanacearum as in the tomato bacterial wilt (Hayward, 1994). Due to this infection, chilli leaves wither off as the initial symptom and subsequently, the entire plant wilts with no yellowing of leaves while brown colour lesions appear in the root area. According to a study done in Brazil, bacterial wilt infection of Capsicum was due to Ralstonia solanacearum (biovar III). Field observations have further indicated that biovar III isolates have been apparently more virulent and aggressive for Capsicum species by inciting severe wilt and vascular discolouration while biovar I induces less severe symptoms and dwarfism and partial wilting even under disease favourable conditions (Takatsu & Lopes, 1997;Coelho Neto et al., 2003).
Several control strategies have been tried out in managing the bacterial wilt infection in Capsicum annuum worldwide ( Table 4).
Cultivation of resistant chilli varieties is one of the promising approaches in effective control of this highly variable bacterial infection in solanaceous crops (Peter et al., 1993;Hartman & Elphinstone, 1994;Wang et al., 2000). Wang & Berke (1997)   ,  and . Lopes and Boiteux (2004), studied and evaluated the reaction of Capsicum accessions (23 previously selected as bacterial wilt resistant and two susceptible controls) to R. solanacearum biovar I or III isolates.
The main control measures taken against the Fusarium wilt infection of chilli worldwide are biological green approaches such as the application of biological control agents: antagonistic microorganisms, botanicals, induction of host systemic resistance etc. However, only one study was carried out on chilli wilt in Sri Lanka (Kelaniyangoda, 2011). As reported, the chilli wilt detected in Sri Lanka is caused as a result of a series of fungal infections and not due to a bacterial infection. Chemical treatments have been tested and were successful in reducing chilli wilt in Sri Lanka caused by Fusarium sp. (Kelaniyangoda et al., 2011). It had been mentioned that a controlled irrigation supplement was also important in the management of the disease. In comparison to efforts elsewhere in using biological control measures for the management of the disease, no such strategies have been studied in Sri Lanka.

Other wilt infections in chilli
Wilt in chilli could also result from infections of Phytophthora spp., Pythium spp., Rhizoctonia solani and Verticillium dahlia. Phytophthora root rot is caused by the fungus-like organism Phytophthora capsici. Infection of the root and lower portions of the stem leads to plant wilting. Gradually wilting is displayed over the entire field. Phytophthora capsici produces zoospores, which enable the spread of the pathogen from plant to plant. Management of P. capsici involves reducing soil water saturation, using resistant cultivars if available, reducing populations of the pathogen through crop rotation, soil solarization, application of organic amendments, restricting pathogen dispersal through mulching and the judicious use of fungicides such as metalaxyl or mefenoxam (Ristaino & Johnston, 1999).
Verticillium wilt of chilli is caused by Verticillium dahliae and V. albo-atrum. Visual symptoms of the disease include stunting, defoliation, and wilting, with discoloration of the vascular system. In the field, the disease first appears in a single plant or a small group of wilting plants scattered throughout the field, depending on the distribution of the pathogen in the soil. The disease gradually spreads and may cover the entire field. Infected plants may exhibit physiological changes such as the reduction in photosynthesis, increased plant transpiration, and respiration.
Although a tremendous effort has been made to identify resistance to Verticillium wilt, it has still not been successful, as currently there are no commercially acceptable cultivars that are genetically resistant to this disease. Application of chloropicrin and metamsodium fumigants and the use of organic amendments, may decrease Verticillium wilt through reduction of pathogen populations in the soil (Lazarovits et al., 2000).
According to Kelaniyangoda et al., (2011), species of Fusarium, Pythium and Phytophthora are responsible for the chilli wilt disease in Sri Lanka. As they further report chilli plants initially get infected by oomycetes such as Pythium and Phytophthora and subsequently become susceptible to infections of Fusarium sp. This primary infection of Pythium and Phytophthora spp. does not result in any visible symptoms.
However, the secondary infection of Fusarium spp. is visible and results in wilting of the chilli plants. Studies on this infection in Sri Lanka are lacking but is much needed to make the cultivation of chillies more profitable.
This review clearly emphasizes the validity to carry out more detailed studies on tomato and chilli wilt infections in Sri Lanka and to formulate more effective control strategies to meet the increasing demand for these crops.

Conclusion
Wilt diseases of tomato and chilli are common, economically important infection in both crops worldwide. It was reported that tomato wilt is caused mainly by bacterial (R. solanacearum) and fungal (Fusarium spp.) infections while