Phylogenetic relationship and identification of Pyricularia species causing blast disease in pearl millet ( Pennisetum glaucum )

In the present study, multi-locus phylogenetic analysis based on the actin, β-tubulin, and calmodulin gene sequences was used to assess the genetic diversity and evolutionary relationships among Pyricularia isolates collected from pearl millet, rice, finger millet, foxtail millet, and various weed species. The analysis also aimed to confirm the identity of Pyricularia spp. causing blast in pearl millet. Most of the isolates from pearl millet and associated weeds (Brachiaria ramosa, Imperata cylindrica, and Cenchrus spp.,) were clustered separately from those infecting rice, finger millet, and foxtail millet. A subset of eleven pearl millet isolates consistently formed a distinct lineage across all three gene trees. The sequences of Magnaporthe salvini, M. rhizophila, M. poae, M. grisea, M. oryzae, Pyricularia pennisetigena and P. penniseticola isolates for actin, and calmodulin genes from the NCBI database were also included for species identification. Based on multilocus clustering, the 11 pearl millet isolates, which clustered separately in all three gene trees, were identified as P. penniseticola, whereas the remaining 48 pearl millet isolates and 12 weed isolates were identified as P. pennisetigena. Actin, and calmodulin genes-based haplotype analysis generated phylogenetic cluster/species-specific unique haplotype fingerprints. These findings also indicate the need to investigate the role of weed hosts in epidemiology of pearl millet blast and to examine the distribution patterns of P. pennisetigena and P. penniseticola across diverse pearl millet growing ecologies.