Molecular Diversity and Mating Type Distribution of the Rice Blast Pathogen Magnaporthe oryzae in North-East and Eastern India

Rice blast, caused by Magnaporthe oryzae, is the most devastating disease of rice and severely affects crop stability and sustainability worldwide. In this study, a total of 63 single spore isolates, collected during 2010-2013 from different cultivars in the different rice growing regions of North-East and Eastern India were used for molecular diversity and mating type analysis. DNA fingerprinting was used to study the diversity among the collections of 63 isolates by using POT2-TIR rep-PCR and MGR586-TIR. Different lineages were detected for 63 M. oryzae isolates by Pot2-TIR and eight for MGR586-TIR fingerprints at 75 % similarity. Among the lineages detected by Pot2-TIR, lineage A and I represented the maximum number of isolates whereas other lineages represent fewer numbers of isolates. Generally all the lineages contained isolates of mixed geographical origin. Isolates from Jharkhand were distributed in all the seven lineages. The MGR586-TIR DNA fingerprinting detected eight lineages, out of which three (Lineages F, G, H) were site specific but were represented only by single isolate. Lineage C contained isolates of Jharkhand only. The lineage A was the largest represented 46 isolates from all the states except Madhya Pradesh. Optimization of the sampling may result in considerable improvement in the results as clustering of isolates from Jharkhand in a few lineages and detection of different lineages with limited isolates from other states could be ascribed to improper sampling. MGR586-TIR fingerprints appeared to differentiate the isolates more strongly compared to POT2-TIR as is obvious from the distance among isolates of the same lineage (Lineage A) arbitrarily grouped together at 75 % similarity. All the 63 isolates were also investigated for MAT1-1 and MAT1-2 mating-type distribution by PCR based molecular markers. Of the 63 M. oryzae isolates collected, 16 (25 %) of the isolates were the mating type MAT1-1 while 35 (56 %) were mating type MAT1-2. The MAT1-2 isolates predominated in Jharkhand and Assam while MAT1-1 is more predominant in the isolates of Odisha. Both MAT1-1 and MAT1-2 were equally distributed in the isolates of Meghalaya and Tripura. Only single isolate from Jharkhand was positive for both the mating type. The results indicated that sexual recombination might be the one reason for lineage diversity in M. oryzae in fields of large rice-growing regions in North-East and Eastern states of India.