Phenotypic screening and molecular marker-based identification of resistant apple genotypes to Eriosoma lanigerum in Kashmir, India

Phenotypic screening of nine apple genotypes (Shireen, Chamura, American Apirouge, Red Delicious, Vance Delicious, Royal Delicious, Lal Ambri, Akbar and Top Red) revealed significant variation in susceptibility to woolly apple aphid ( Eriosoma lanigerum ) infestation during April–October 2025. Infestation peaked in mid-summer, with Vance Delicious and Akbar showing extreme susceptibility, while American Apirouge consistently maintained low colony counts. Cumulative infestation scores ranged from 595 in Vance Delicious to 315 colonies of WAA in American Apirouge. The findings highlight substantial genotypic differences in resistance. American Apirouge emerges as a promising genotype for resistant to woolly apple aphid among the nine genotypes. Molecular marker analysis of nine apple cultivars revealed key genetic determinants of resistance to woolly apple aphid ( Eriosoma lanigerum ). Conserved markers NZsc_GS327, NZsc_O05, NZms_EB145764, NZms_EB106753, NZsc_E01 and NZsc_A01 were consistently detected across most genotypes, underscoring their strong association with resistance. A distinct finding was the presence of NZsc_C20, linked to the Er1 gene, exclusively in ‘American Apirouge’, suggesting a unique resistance pathway. In contrast, NZsn_O05 was absent in all cultivars, confirming its lack of relevance in resistance determination. The combined genotypic and phenotypic evaluation demonstrated a strong correlation between marker presence and field resistance, with ‘American Apirouge’ showing the lowest infestation, while ‘Vance Delicious’ and ‘Akbar’ recorded higher susceptibility despite carrying most markers. These results highlight the importance of both conserved and cultivar‑specific alleles in shaping resistance and provide valuable insights for aimed at durable woolly aphids’ control.