Yield Loss Assessment in Cowpea Genotypes due to Stem and Root Rot Caused by Macrophomina phaseolina

Cowpea crop suffer from various stresses, both biological and environmental, that reduce their quality and yield, leading to significant economic losses. Stem and root rot caused by Macrophomina phaseolina is a major root disease responsible for yield losses of 50-55 per cent.

A study was conducted by the Department of Plant Pathology, University of Agricultural Sciences (UAS), Dharwad, Karnataka, India, during the rabi season of 2022-23 to assess the impact of Macrophomina phaseolina infection on cowpea yield in split plot design. Ten released cowpea genotypes (C 152, DC 15, DC 16, DCS 47-1, KBC 11, KBC 9, KM 5, PKB 6, PKB 4, IT 38956-1) were grown in plots that were both inoculated and uninoculated with M. phaseolina.

The disease caused an estimated grain yield loss of 19.64-43.74 per cent in all the genotypes. The moderately resistant genotype KBC 9 had the lowest grain yield loss (19.64%), while the farmer preferred genotype C 152 was susceptible to the root rot disease and had high yield loss of up to 43.74 per cent. among the genotypes, KBC 9 showed the highest reduction in stem and root rot incidence (78.22%), followed by IT 38956-1 (77.68%) while C 152 had the lowest root rot reduction (70.34%) when compared to pathogen inoculated plots. The principal component analysis (PCA) of different yield parameters of cowpea genotypes shows that, first four components (PC-1 to PC-4) with Eigen values of 4.16, 1.47, 1.29 and 1.14, collectively explained 89.82 per cent of the total variance. PC-1 (46.32% variability) was primarily influenced by the number of pods per plant, root length, root nodules per plant and plant height. Seed yield was significantly (p≤0.05) and strongly correlated to number of root nodules per plant (r=0.50) and root length (r=0.49).