Chickpea (Cicer arientinum L.) is an important annual legume crop of the family Fabaceae. Different abiotic and biotic agents affect adversely chickpea productivity around the world. Wilt disease is a major constraint to chickpea production due to the occurrence of wilt of chickpea causal organism of wilt Fusarium oxysporum f. sp. ciceri (Padwick) synd. and Hans. It produces microconidia, macroconidia, and chlamydospores. Among all surveyed districts, disease incidence ranged from 9.17 to 23.40 per cent with an overall mean of 17.05 per cent in Rajasthan. The highest mean disease incidence was observed in Ajmer district (23.40%) followed by Pali (21.10%), Jaipur (20.16%), Bhilwara (17.86%), Tonk (17.73%), Sikar (15.81%), Bikaner (11.19%), and lowest was in Churu district (9.17%).  Not a single location of surveyed districts was completely free from the disease incidence.

Fusarium oxysporum f. sp. ciceri, Chickpea wilt, Percent disease incidence.

Chickpea (Cicer arientinum L.) is an important annual legume crop of the family Fabaceae. It is one of the primitive crops of the world that originated in South-eastern Turkey about 8000-9000 years ago from its wild ancestor C. reticulatus (Dhawale and Dhale 2021). Different abiotic and biotic agents affect adversely chickpea productivity around the world. Chickpea is very sensitive to biotic stresses from a variety of organisms such as fungi, bacteria, viruses, mycoplasma, and nematodes. Worldwide around 172 infectious pathogens have been recorded which are harmful to Chickpea (Navas-Cortes et al., 1998).

Wilt disease is a major constraint to chickpea production due to the occurrence of wilt of chickpea causal organism of wilt Fusarium oxysporum f. sp. ciceri (Padwick) synd. and Hans. It produces microconidia, macroconidia, and chlamydospores. The wiltof chickpea is a root-occupying, soil-borne organism. No unequivocal information is accessible regarding trim misfortunes. In long periods of extreme pestilence, crop misfortunes have shot up as high as 60-70%. At the seedling and blossoming stage, loss of yield was 59% and 41% individually (Dhawale and Dhale 2021). Seeds gathered from wilt-infected plants indicate low weightage, more bluntness, and wrinkles than from normal plants. The yield misfortunes fluctuate somewhere in the range of 10% and 100% depending upon the agro-climatic conditions.

A. Survey and incidence of disease

A survey in major chickpea growing districts viz., Bikaner, Ajmer, Tonk, Jaipur, Churu, Sikar, Pali, and Bhilwara was undertaken during the last week of December to the first week of January. The survey was conducted during the Rabi season of 2020-21. Two tehsils under each district will be surveyed. In each tehsil, two villages will be selected and under each village three farmer’s fields will be assessed. The selection of two villages from each tehsil was made randomly. To assess the disease incidence, five chickpea fields were selected in each village in each tehsil of each district, and the average incidence of the disease in each village was calculated. In each field, five spots of one square meter area were marked diagonally randomly to cover the entire field. Diseased and healthy plants were counted in each spot and the percent disease incidence was calculated as per the formula given below

B. Collection of diseased samples

Wilt-affected plants of chickpeas were collected from surveyed areas of Rajasthan viz., Bikaner, Ajmer, Tonk, Jaipur, Churu, Sikar, Pali, and Bhilwara. The samples of diseased plants were used for isolation of the causal fungus. Isolation was done from the diseased roots of chickpea samples, collected during a survey from the fields showing a higher percent of disease incidence.

A. Survey and occurrence of disease

A roving survey was conducted during the Rabi season of 2021-22 in major chickpea-growing districts of Rajasthan covering eight districts viz., Sikar, Pali, Ajmer, Tonk, Jaipur, Bikaner, Churu, and Bhilwara comprising five agro-climatic zones in the state.  During the survey, a total of 96 fields in 32 villages of sixteen tehsils of eight districts were covered and in each village three fields were chosen. To assess the disease incidence, three chickpea fields were selected in each village and the average incidence in each village was calculated. The survey revealed that the wilt caused by the Fusarium oxysporum f. sp. ciceriis an important pathological problem in chickpea-growing districts. Wilt incidence was observed in all the surveyed fields of eight districts. During the survey, farmers who were concerned about disease prevalence and severity had a little discussion. According to the survey's findings presented in Plate-2.It is apparent from data (Table 1-2 and Fig. 1) that every surveyed field revealed the presence of Fusarium wilt and it ranged from 9.15 to 23.40 per cent with an overall mean of 17.05 per cent. The highest mean disease incidence was observed in Ajmer district (23.40%) followed by Pali (21.10%), Jaipur (20.16%), Bhilwara (17.86%), Tonk (17.73%), Sikar (15.81%), Bikaner (11.19%), and lowest was in Churu district (9.17%). Kishangarh tehsil in Ajmer district had the highest mean disease incidence of 23.75 per cent, followed by Ajmer tehsil with 23.06 per cent. Rajgarh tehsil in Churu district had the lowest mean disease incidence, with 9.15 per cent, followed by Taranagar tehsil with 9.20 per cent. Disease incidence was found maximum in local varieties compared to improved varieties of chickpea. 

Table 1: Percent disease incidence of wilt of chickpea induced by Fusarium oxysporum f. sp. ciceri in different districts of Rajasthan in Rabi 2021-22.

PDI = Per cent disease incidence

Fig. 1. Percent disease incidence of wilt of chickpea induced by Fusarium oxysporum f. sp. ciceri in different districts of Rajasthan in Rabi 2021-22.

Table 2: Per cent disease incidence of wilt of chickpea induced by Fusarium oxysporum f. sp. ciceri in different districts of Rajasthan in Rabi 2021-22.

*Representative isolate of each village surveyed district was established from the field showing highest PDI

Wilt-affected plants appeared in all the surveyed fields. Samples were collected along with information such as cultivars, soil type, number of irrigations, and disease appearance. Among all surveyed districts, disease incidence ranged from 9.17 to 23.40 per cent with an overall mean of 17.05 per cent in Rajasthan. The highest mean disease incidence was observed in Ajmer district (23.40%) followed by Pali (21.10%), Jaipur (20.16%), Bhilwara (17.86%), Tonk (17.73%), Sikar (15.81%), Bikaner (11.19%), and lowest was in Churu district (9.17%).  Not a single location of surveyed districts was completely free from the disease incidence. As per verbal discussions held with the farmers during the survey, it can be summarized that the disease incidence was higher in fields where mono-cropping with local cultivars followed year after year in sandy loam to sandy soils. As compared to improved varieties, local varieties were found more susceptible to Fusarium oxysporum f. sp. ciceri. 

Similar results were also reported by Chand and Khirbat (2009) that the pathogen is highly variable in its cultural characteristics and pathogenicity. Yield losses vary between 10 to 100% depending on varietal susceptibility and agroclimatic conditions. 

Sunkad et al. (2019) chickpea is affected by both biotic and abiotic stresses which lead to a decline in production. Wilt disease caused by the fungus i.e., Fusarium oxysporum f. sp. ciceri (Padwick) is a destructive disease recording major productivity loss in all chickpea growing areas worldwide. Early wilting (77–94%) and late wilting (24–65%) are two stages of disease incidence.

A survey was conducted in the 2014-2015 Rabi season to obtain information on the distribution and incidence of chickpea wilt in respect of soil type and irrigation condition. Local cultivars were predominant inmost farmer's fields. Wilt disease was found at all the sites and incidence ranged from 1.69 to 18.67%irrespective of cultivar type and location. The result indicated that wilt is recently highly distributed in all visited chickpea-growing areas of the central part of India. The wilt incidence was higher in rainfed conditions (11.37%) as compared to irrigated conditions (7.56%). Based on the survey, deep black soil was found most suitable for wilt development.

Similarly, results were found by Nathawat et al. (2020) wilt disease of chickpea was found to be prevalent in all districts of Rajasthan surveyed. The disease varied from mild to severe in Sikar, it was maximum of 31.90 per cent followed by Hanumangarh, Sriganganagar, and Jaipur in 2015-16. The least wilt disease incidence was observed 19.75 percent in the Tonk district.

The survey revealed that disease incidence was significantly higher in fields having a higher number of irrigations as compared to the fields receiving less irrigation. It was also noted that wilt incidence was higher where the crop was cultivated in the lighter textured soil of Rajasthan. The highest incidence was found in sandy loam soil in the surveyed areas of Rajasthan, the variation in disease incidence might be due to the use of varieties of soil types and applied of variable disease management practices.

Kewal Chand, S.K. Goyal, R.P. Ghasolia, Shalish Godika and Ranjana Meena  (2024). Roving Survey of Chickpea Wilt Incited by Fusarium oxysporum f. sp. ciceri in Rajasthan, India. Biological Forum – An International Journal, 16(7): 68-71.