Survey and assessment of severity of early blight (Alternaria solani) disease of tomato in Jodhpur district of Rajasthan

摘要

The Portuguese introduced the tomato (Solarium lycopersicum L) to India in the 1700s (Kale and Kale, 1994). Tomato is also known as “Poor Man’s Orange” in India because it is a nutrient-dense super food and an excellent source of antioxidants, which help to reduce the risk of heart disease and cancer. That’s why there is a lot of demand for tomatoes throughout the year. Being the world’s fourth most cultivated crop with a production of 130 million tones and area of to 5.2 million hectares, tomato is an inevitable vegetable crop world over and of course, for India. India is a second largest producer of tomato after China having an area of 778 thousand hectares with a production of 19397 metric tons and share 11% of world production (Anonymous, 2020). In Rajasthan state, tomato is grown over an area of 18.12 thousand hectares and with an annual production of 88.73 MT during 2017-18 (Anonymous, 2019). Early blight disease of tomato is one of the most wide spread and exterminatory disease occurring worldwide in major tomato growing area (Akhtar et al., 2019). It is caused by several species of Alternaria including Alternaria solani and A. alternata (Adhikari et al., 2017). In India, Alternaria solani from tomato was first reported by Butler in 1905 in Faizabad district of Uttar Pradesh. Worldwide, early blight disease caused most prevalent and destructive foliar disease of tomato resulting up to 78% yield and production loss (Datar and Mayee 1981; Bessadat et al. 2014). It directly undermines the plant and reduces the quantity and quality of the economic yield. This disease, in severe condition can lead to complete defoliation and it cause epidemic in regions with heavy rainfall, high humidity and fairly high temperatures 24-29°C (Peralta et al. 2005). The symptom of early blight of tomato appears on aerial part of the plant such as leaves, stem and fruits. On leaves spots are round brown and can grow up to half inch in diameter. Larger spots have concentric rings appear after sporulation which forms typical "target board" symptoms or bull eye shaped spots, as a result of sporulation pattern. This disease has been noticed in tomato growing area of Jodhpur region of Rajasthan and speculated as major reason behind low productivity. Assessing disease severity is the first step in designing management strategies against any disease. Since there is no report regarding severity and causal agent of early blight disease of tomato in this region, present study aimed to enumerate the disease severityand to find out the pathogens associated with the disease in Jodhpur region.