Prevalence and distribution of Alternaria leaf spot in soybean growing areas of Rajasthan

Abstract

Soybean is one of the most important oil seed crops grown in India with high amount of protein and oil content in it. To understand the prevalence and distribution pattern of Alternaria leaf spot disease a study was carried out in six major soybean growing districts of Rajasthan during kharif 2018-19. The pathogen associated with leaf spot disease was isolated and identified as Alternaria alternata. The study revealed that the disease had more occurrences in those districts where soybean is mainly grown. The maximum percent disease index 22.02-29.08% and 37.52-42.35% was found in Udaipur region followed by Chittorgarh district having PDI 21.33-25.08 and 30.57-37.72% and minimum PDI (14.70-19.39 and 23.27-28.33%) was recorded in Kota region at flowering and pod formation stage during both the years. The favourable temperatures range of 21.8-29.4 °C and relative humidity in the range of 73.3-92.4% for occurrence, development and spread of this disease. The overall PDI was observed more in the year 2019 as compared to 2018. This disease was found to cause severe losses on a wider area under soybean cultivation in Rajasthan.

Keywords

• A. alternata
• Leaf spot
• Percent disease index
• Soybean