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Prevalence of Collar Rot of Tomato Caused by Sclerotium rolfsii (Sacc.) under the Red and Lateritic Zone of West Bengal, India

Tomato (Solanum lycopersicon L.) a member of the family Solanaceae, is the most popular and high-value vegetable crop in the world because of its taste, color and high nutritive value and also for its diversified use. It is the world's largest vegetable crop after potato and sweet potato. Due to its extensive cultivation in non-traditional areas, several biotic and abiotic factors have emerged as a major constraint in its successful cultivation. Among the biotic factors, diseases i.e., collar rot (Sclerotium rolfsii), damping off (Pythium spp.), early blight (Alternaria solani), fruit rot (Phytophthora nicotianae), bacterial wilt (Ralstonia solanacearum), Bacterial fruit canker: (Clavibacter michiganense subsp. Michiganense), Rhizoctonia root rot (Rhizoctonia solani), Tomato spotted wiltTomato Spotted Wilt Virus (TSWV), Tomato Mosaic (Tomato mosaic virus), Root knot nematode (Meloidogyne sp), little leaf (phytoplasmal) are the major diseases of Tomato (Meah, 2003). But recently, the collar rot caused by Sclerotium rolfsii is becoming International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 6 Number 11 (2017) pp. 3231-3236 Journal homepage: http://www.ijcmas.com


Introduction
Tomato (Solanum lycopersicon L.) a member of the family Solanaceae, is the most popular and high-value vegetable crop in the world because of its taste, color and high nutritive value and also for its diversified use. It is the world's largest vegetable crop after potato and sweet potato. Due to its extensive cultivation in non-traditional areas, several biotic and abiotic factors have emerged as a major constraint in its successful cultivation. Among the biotic factors, diseases i.e., collar rot (Sclerotium rolfsii), damping off (Pythium  (Meah, 2003). But recently, the collar rot caused by Sclerotium rolfsii is becoming Tomato (Solanum lycopersicon L.) a member of the family Solanaceae, is the world's largest vegetable crop after potato and sweet potato. Diseases of tomato act as the chief limiting factor to its economic production. Recently, the collar rot caused by Sclerotium rolfsii is becoming sever disease of tomato in India. Crop Losses up to 30 per cent due to collar rot disease have been reported by many researchers in this crop. Hence to get a preliminary idea regarding the incidence level and pattern of prevalence of the disease in the agro-ecological condition of undulating red and lateritic zone of West Bengal, a roving survey was conducted at different locations of the aforesaid agro climatic zone during the crop growing season of 2014-15 and 2015-16. The pooled analysis of two years data revealed that disease incidence was ranged from 7.61 to 21.79 % in this zone and the Purulia district had maximum level of disease incidence ranging from 13.14 to 21.79 % followed by Bankura districts 11.90 to 16.64 %, Birbhum district 9.75 to 17.73%, Burdwan district 7.61 to 14.54 %. Paschim Medinipur district was noticed with less incidence levels ranging from 9.08 to 9.51 %. This study provided an elementary idea about the disease incidence pattern in this zone as well as paved the path for seeking resistance sources under local conditions and recommendation of proper farming practices to combat the drastic effects of collar rot disease.  (Thiribhuvanamala et al., 1999).  reported collar rot caused by Sclerotium rolfsii (Corticium rolfsii) is one of the major threats in Himachal Pradesh, India, with an incidence of 10-45%. The disease is distributed in tropical and sub-tropical regions of the world where high temperatures prevail. Sclerotium rolfsii, the causal agent of collar/foot rot of many crops (Aycock, 1966) having a wider host range (Talukdar, 1974 andBhattacharrya et al., 1977) attracted the attention of plant pathologist and professional researcher throughout the world. The pathogen is known to cause diseases of cereals, pulses, oil crops, potatoes, vegetables, ornamentals, and nursery seedlings of fruits and forest trees (Bertus, 1929). The pathogen is a soil inhabitant, very aggressive nature, attacks the collar portion of plant, which ultimately leads to its death. The infection leads to the drying of lower leaves and eventually the whole plant dries giving a typical symptom of wilting. The collar rot of tomato may occur at any growth stage of the plant (Begum et al., 1985). The disease has been reported by many workers in different agro climatic zone of West Bengal. But accurate information of natural incidence level of the disease particularly in the undulating red and lateritic zone of West Bengal is scanty. Inadequate knowledge about the incidence level of the disease, their distribution pattern etc. leads the use of chemicals indiscriminately. Therefore the present study was carried to find out the occurrence and distribution pattern of collar rot disease of tomato in the agro-ecological condition of undulating red and lateritic zone of West Bengal.

Materials and Methods
To estimate the natural incidence of collar rot disease of tomato under the agro-ecological condition of undulating red and lateritic zone of West Bengal, surveys were carried out during the crop growing season of 2014-15 and 2015-16 in different district of undulating red and lateritic regions of West Bengal which include part of Birbhum, Bankura, Purulia, Burdwan and Paschim Medinipur, where tomato crops was cultivated extensively by the farmers.
In each place, field of more or less uniform size was selected at random and observation on the incidence of the diseases was recorded. Percent disease incidence was calculated by using the following formula.

Results and Discussion
To obtain information on the natural incidence of collar rot of tomato, surveys were conducted during the growing season (November' 2014-April' 2015and November' 2015-April' 2016 in different locations of undulating red and lateritic zone of West Bengal i.e. Birbhum, Burdwan, Bankura, Purulia and Paschim Medinipur districts to record the incidence of the disease. The recorded data of disease incidence have been presented in the table 1 and 2. It was evident from both the tables that the incidence of collar rot disease of tomato varied with the location and season. The incidence of the collar rot disease ranging from 7.36 % to 21.06 % was obtained during 2014-15 (Table 1)  Photo Plate.1 Categorization of districts of red and lateritic zone of West Bengal based on prevalence of collar rot of tomato caused by Sclerotium rolfsii. (+) sign refers to the degree of prevalence of disease with (+++++) for maximum and (+) for minimum prevalence and subsequent degree of prevalence accordingly as per no. of (+) sign  While comparison of the incidence level of collar rot disease in five districts, the pooled analysis (Table 3 and Fig. 1) indicated that the Purulia district had maximum level of disease incidence ranging from 13.14 to 21.79 % followed by Bankura districts 11.90 to 16.64 %, Birbhum district 9.75 to 17.73%, Burdwan district 7.61 to 14.54 %. Paschim Medinipur district was noticed with less incidence levels ranging from 9.08 to 9.51 % during seasons under surveyed (Photo plate 1). Higher incidence of collar rot of tomato in Purulia and Bankura districts in comparison to Burdwan, Birbhum and Paschim Medinipur districts was probably due to the higher range of soil and atmospheric temperature which help the pathogen Sclerotium rolfsii for faster multiplication and growth in soil and sandy clay loam soil fulfil the high oxygen demand for survival of sclerotia.  reported collar rot of tomato (Sclerotium rolfsii) is one of the major threats in Himachal Pradesh, India, with an incidence of 10-45%. Thiribhuvanamala et al., (1999) observed that 30 per cent of crop loss in tomato was due to S. rolfsii. Ingale and Mayee, (1986) reported that 25 per cent of seedling mortality in the cultivar JL-24 of Groundnut at Parbhani due to S. rolfsii. Naidu (2000) reported that S. rolfsii caused 40-50 per cent mortality in crossandra in Chittoor district of Andhra Pradesh. In Chickpea, upto 30 percent disease incidence reported in Jabalpur by Padole et al., (2009). In Saurashtra, Gujarat, 30-40% seedling rot reported on garlic (Lukose et al., 2003). Collar rot caused by S. rolfsii is the most destructive disease of tomato in Bangladesh (Talukder, 1974). The above information's are in line of the present findings.
The results obtained in this experimental study revealed that the collar rot of tomato caused by Sclerotium rolfsii was prevalent in all the districts of undulating red and lateritic agro-climatic zone of West Bengal (India). The district Purulia showed maximum prevalence of collar rot whereas minimum prevalence was recorded in Paschim Medinipur district. The higher range of soil and atmospheric temperature and continuous cultivation of susceptible cultivars over years were responsible for high prevalence of collar rot in these locations. The finding emphasize on seeking new resistance sources under local conditions and encouraging of sowing resistance cultivars by following good management practices.