Postulation of putative host differentials and pathotyping of Pyricularia setariae (Nishikado) causing leaf blast on foxtail millet [Setaria italica (L.) Beauv] in India

The present investigation attempted to postulate foxtail millet genotypes as putative host differentials for studying pathogen variability. Initially, a diverse panel of 95 genotypes were evaluated against foxtail millet leaf blast under field conditions at four different hotspot locations viz., Bangalore, Mandya. Nandyal and Vizianagaram during Kharif 2021. Based on the field reaction, 22 genotypes were selected for further screening under glasshouse conditions along with ISe175 (resistant check) and SiA326 (susceptible check). Four (4) leaf blast isolates namely FoxPs-3, 5, 6 and 15 from different locations were used to identify putative host differentials based on differential reaction. A set of 12 putative host differentials viz., ISe1256, GS55, GS2261, ISe1408, GS73, ISe1299, GS101, ISe746, ISe1655 and ISe1745 along with a resistant (ISe175) and susceptible check (SiA326), showing differential host responses were proposed as candidate host differentials to assess the pathogenic variability. The pathogenic profiling of 15 isolates on the identified putative host differential set has revealed four major pathogenic groups indicating the existence of pathotypes in Pyricularia population infecting foxtail millet in India. A set of putative host differentials identified and information on pathotypes of P. setariae is highly useful in better understanding of host pathogen interaction, existence of pathotype in a crop ecosystem and also serve as tools for identification of suitable disease resistant genotypes for resistant breeding programme.