Deciphering genotype by year interaction for tea mosquito bug incidence (Helopeltis spp.) in Indian cashew (Anacardium occidentale L.) germplasm

Cashew (Anacardium occidentale L.) is a predominant tree crop cultivated in tropical and subtropical regions of the world. The crop is plagued by the regular incidence of polyphagous insect pest tea mosquito bug (TMB) (Helopeltis spp.). TMB causes 30–50% nut yield loss in regular incidences and up to 100% in epidemic situations. The incidence of TMB is prevalent in most of the cashew growing regions but research on the interaction between TMB and year has not been undertaken. To this end 15 cashew germplasms were evaluated for TMB incidence from 2016 to 2022 to study the stability of TMB incidence in cashew. TMB damage scores was analyzed following additive main effect and multiplicative interaction (AMMI) and genotype and genotype by environment (GGE) methods. Years (Y) differed significantly (P ≤ 0.01) whereas genotypes (G) (P = 0.18) and G × Y interactions were not significant (P = 0.96). The variations explained by G, Y and G × Y were 7.15%, 37.05% and 17.18% respectively. The total variability captured by the first two incremental principal component analysis (IPCA) viz., IPCA 1 (49.83%) and IPCA 2 (29.49%) was 79.32%. Accessions NRC 112, 144, 75 and 176 won in the first mega environment and NRC 120, 140, 189 won in second, third and fourth mega environments respectively. Three accessions NRC 301 (0.511), V-8 (0.567) and NRC 270 (0.734) with least TMB incidences were found stable and could serve as useful candidate genotypes in cashew breeding programme for TMB tolerance.