Characterization and correlation of pathogenicity of Botryodiplodia theobromae isolates, the causal agent of black root rot of mulberry (Morus spp.)

The study reports the characterization of 10 isolates of mulberry black root rot causing fungus, Botryodiplodia theobromae obtained from the infected gardens of Karnataka, Andhra Pradesh and Tamil Nadu. The analysis based on cultural, morphological, pathogenicity and molecular markers (RAPD and SSRs) revealed significant variations among the isolates. Based on the disease reaction on susceptible V-1 variety, isolates were grouped as pathogenic (60%), moderate pathogenic (20%) and non-pathogenic (20%). Among all isolates, RAPDs revealed higher marker polymorphism however, based on Shannon’s Information Index (I) SSRs were more informative (0.781) compared to the former (0.444). Stepwise Multiple Regression Analysis (MRA) indicated a total of 5, 5 and 3 molecular markers were found to correlate with disease symptoms. Screening of germplasm using multiple strains of virulent isolates will enhance possibilities of locating diverse resistant genes. Pyramiding of these genes will aid in development of mulberry variety with durable resistance and sustainable sericulture.