Genome Wide Comparison of Rice and Non-Rice Magnaporthe Isolates from Southern India

Rice, wheat and millets are the most important staple cereals in India. Blast disease caused by Magnaporthe species is a major factor affecting productivity of these important food crops. Rice blast disease caused by Magnaporthe oryzae is a well-known model system to study plant-fungal interactions. The Magnaporthe species complex comprises of many phylogenetic species that cause diseases on over 50 grass species. In this study, we aimed genome-wide comparative study of Magnaporthe isolates, which infects rice and non-rice host species from Southern India. Whole genome sequences for four rice and six non-rice isolates (finger millets and grasses) were generated using Illumina sequencing technology. This comparative study displayed high genetic variation between rice and non-rice isolates. Repeat elements such as Pot2, Maggy and Mg-SINE were found to be significantly enriched in rice isolates in comparison to finger millet and grass isolates. Clustering of orthologous genes, revealed expansions of gene families such as beta-glucosidase, alpha-mannosidase, chitin synthase and ABC transporter CDR4, which play an important role in fungal virulence and growth. Additionally, the orthologous clustering gave a deeper insight into host specific genome content. Most of the isolate specific genes were found to be novel uncharacterized proteins. This is the first whole genome study of tropical rice and non-rice Magnaporthe isolates and will widen the understanding of fungal virulence spectrum.