Integration of BSA-Seq and RNA-Seq Identifies CND41 as a Key Candidate Gene for Early Blight Resistance in Potato

Potato early blight (EB), caused by Alternaria, is an economically devastating fungal disease affecting global potato production. Using a hybrid population derived from distantly related varieties, we combined resistance evaluation, histological analysis, Bulked Segregant Analysis sequencing, RNA sequencing and molecular dynamics simulation, which successfully identified key candidate resistance genes. Genetic mapping localized three major resistance-associated regions on chromosome 8 spanning positions 25.07–29.20 Mb, 38.05–38.80 Mb, and 39.40–40.78 Mb. Through candidate gene analysis, we identified CND41, encoding an aspartic protease, as the prime candidate. This gene exhibited significantly higher basal expression levels and stronger pathogen-induced upregulation in resistant genotypes. Molecular dynamics simulations further identified six crucial non-synonymous mutations in the TAXI-N domain that likely contribute to enhanced resistance by destabilizing the susceptibility-associated protein conformation. Transient overexpression of CND41 provided functional evidence supporting its likely involvement in early blight resistance (EBR). These findings contribute valuable genetic resources and a strong candidate gene for molecular breeding toward EBR potato varieties.