Genetic variability and trait association studies in cashew (Anacardium occidentale L.)

Abstract

High seedling mortality during the establishment phase together with low nut yield limit cashew productivity in Ghana. The survival and nut yield of 20 cashew germplasm clones were evaluated at two locations, Wenchi in the Forest Transition and Bole in the Guinea Savannah agro - ecological zones in Ghana. A randomized complete-block design with four replications was used to evaluate the clones for the following traits: seedling survival, vigour (estimated as trunk cross-sectional area, TCSA), height, nut yield, nut size and yield outturn. There were significant (p < 0.05) clone × environment interaction effects for nut yield. The best three highest yielding clones in Bole were SG 266, BE 575 and BE 203 whereas in Wenchi SG 224, SG 266 and SG 014 were the highest yielding clones. Genotypic co-efficient of variation (GCV) of nut yield (24.5%), TCSA (15.9%) and height (14.9%) were higher than those of other traits (3.0–4.5%). Height, TCSA, nut yield and outturn were found to be under moderate genetic control for the two locations combined whereas survival and nut size were under low genetic control. Broad sense heritability ranged from 0.56 ± 0.04 - 0.11 ± 0.01 for height and nut size respectively. Genetic correlation estimates suggest that selection for TCSA and height might lead to a large increment in seedling survival and early nut yield. Multivariate clustering identified clones with complementary traits. Our results, suggest that there is considerable genetic variability that could be exploited to develop superior cashew hybrids.