Evaluation of genetic diversity in Magnaporthe grisea populations adapted to finger millet using simple sequence repeats (SSRs) markers

Finger millet blast caused by Magnaporthe grisea (anamorph: Pyricularia grisea) is a great threat to finger millet production worldwide. Genetic diversity and population structure of 72 M. grisea isolates collected from finger millet (56), foxtail millet (6), pearl millet (7) and rice (3) from major crop growing areas in India was studied using 24 SSR markers. None of the SSRs detected polymorphism in the M. grisea isolates from pearl millet. Seventeen SSR markers were polymorphic in the 65 non pearl millet isolates and detected 105 alleles, of which one was rare, 83 common, 9 frequent and 12 most frequent. A model-based population structure analysis of the genomic data identified two distinct populations with varying levels of ancestral admixtures among the 65 M. grisea isolates. Analysis of molecular variance (AMOVA) indicated that 52% of the total variation among the isolates used in this study was due to differences between the pathogen populations adapted to different hosts, 42% was due to differences in the isolates from the same host, and the remaining 6% due to heterozygosity within isolates. High genetic variability present in M. grisea isolates calls for the continuous monitoring of M. grisea populations anticipating blast resistance breakdown in finger millet cultivars grown in India.