Yield Loss Assessment Due to Alternaria Leaf Spot in Soybean Incited by Alternaria alternata

Abstract

Soybean (Glycine max L.) is one of the most valuable oil seed crops grown in India with high amount of protein and oil content in it. Alternaria leaf spot of soybean is one of the major destructive disease of soybean in recent times and many districts of Rajasthan showing decline in yield. Hence, the present investigation was undertaken to study the yield losses assessment in soybean caused by Alternaria leaf spot. The soybean cultivar RKS-24 was sown in 24 plots with each plot measuring 3.0 X 3.6m. One set of plots was kept inoculated protected from disease by regular application of recommended fungicides and the other set inoculated unprotected served as a control. Maximum per cent disease index (63.5 and 65.8%), grain yield (992.59 and 948.14 kg ha-1) and recovery of A. Alternate from infected seeds (71.0 and 73.0%) was recorded in inoculated unprotected control plots over inoculated protected plots during both the years, respectively. On the basis of difference obtained in net yield between inoculated protected and inculcated unprotected plots, the mean quantitative yield loss was estimated as 45.2% during both years, respectively. These observations suggest that the Alternaria leaf spot has good potential of damaging the crop, and may become a limiting factor in realization of good yields and causing complete failure of the crop.