Unravelling the severity landscape of brazilian Magnaporthe oryzae Triticum on wheat cultivars with and without 2NVS translocation.

Wheat blast caused by Magnaporthe oryzae Triticum (MoT) threatens wheat production, affecting plants at various growth stages. Resistant cultivars, linked to the 2NVS chromosomal translocation, offer potential control strategies, though questions persist about their effectiveness against diverse MoT isolates. This study aimed to (a) characterise and compare the virulence of 77 MoT isolates from wheat cultivated in Brazil based on the reaction of a set of 11 wheat cultivars to the pathogen infection; (b) characterise and compare the wheat genotypes based on their response to infection by MoT isolates, and correlate the presence of the 2NVS translocation; and (c) identify effector genes and their variations among isolates through whole-genome sequencing of a subgroup of 25 representative Brazilian MoT isolates and analyse the effectors concerning the isolates' severity. A randomised design measured blast severity on detached wheat heads 7 days post-inoculation. Significant genotype-by-isolate interactions were observed, revealing that some isolates caused severe symptoms even in cultivars carrying 2NVS. Resistance conferred by 2NVS depended on the genetic background of the cultivars. Cultivar BRS 229, lacking 2NVS, exhibited great resistance, comparable to Jagger and Santa Fe. Effector gene analysis identified 47 candidate genes, seven of which showed variations correlating with isolate aggressiveness. The findings highlight the complex interaction between MoT virulence and wheat genotypes, underscoring the need to broaden resistance strategies. These results provide essential insights into managing wheat blast, emphasising the importance of integrating genetic diversity in resistance breeding programmes, and the sequencing of 25 complete MoT genomes in this study provides a critical genomic foundation for future research in this important pathogen.