Mining genetic resources for stable resistance to Alternaria blight disease of linseed ( Linum usitatissimum L.)

Multi-environment screening of 2579 linseed accessions from the National Genebank of India was undertaken to identify novel donors imparting resistance to Alternaria lini causing blight disease of linseed. Alternaria blight incidence showed a differential genotypic response in the degree of disease severity across different location-year environments. The comparative analysis of disease incidence across two locations revealed that the mean leaf blight was higher at Raipur ( 81%) compared to Kanpur (43.83%), while mean bud blight was comparatively higher (up to 14.86%) at Kanpur than Raipur ( 4%). Leaf and bud blight scores across multiple environments revealed only 3.41% of the tested germplasm (4 resistant and 84 moderately resistant accessions) showed resistance to A. lini infection. Based on pooled disease incidence scores, a small and representative 'Reference Set for Alternaria blight resistance' (RSAB) comprising 256 genotypes was assembled and validated for confirmation of resistance. Overall, one genotype, a selection from IC0591124 was identified as resistant and 14 genotypes (selections from germplasm accessions having National IDs - IC0526066, EC0718850, IC0526032, IC0498580, IC0499140, IC0523800, EC0718852, IC0305053, IC0597268, IC0420772, EC0041481, IC0526017, IC0498549 and IC0597274) were found moderately resistant against all the three isolates of A. lini (Rpr, Knpr and Dli) in up to seven environments including artificial epiphytotic conditions in an environment-controlled glass house. A critical examination of the different quality evaluation criteria revealed that the assembled RSAB effectively captured the representativeness of the whole collection for disease resistance. The RSAB germplasm and novel broad-range resistant genotypes identified in the present study offer valuable insights for breeding programs aiming to develop blight resistant linseed varieties for sustainable disease management. In addition, these genetic resources will be crucial in identifying genes/genomic regions underlying blight resistance through genome-wide association studies and mapping resistance-linked QTLs.