Broadening the Gene Pool of Cashew ( Anacardium occidentale ) for Survival and Precocity

The narrow genetic base of cashew cultivars limits productivity. A germplasm exploration survey (2006–2008) was undertaken to select high-yielding cashew trees (candidate trees) on farmer’s fields across three contrasting agro-ecological zones over a longitude of 6° S and 10° N and a latitude of 4° W and 2° E. High-yielding trees (candidate plus trees) from different zones were grafted and evaluated (2009–2015) with four best clones recommended for farmers for survival, vigor, nut yield and nut weight at Bole (marginal environment) and Wenchi (near-optimal environment) using RCBD with four replications. Shannon–Weiner diversity index ( H ′) for nut yield among candidate trees was higher ( p < 0.001) in the semi-deciduous zone (3.0) than Forest transition (2.6) and Guinea savannah (2.5) zones. There were significant clone × location interaction effects for all traits. Survival ranged from 26.1 to 90%, while nut yields varied from 160.8 to 825 kg/ha/year. The genotypic and phenotypic coefficient of variation for various traits ranged from 12.6–59.01 to 6.23–18% while heritability ( h 2 bs) and genetic gains varied from 0.21–0.48 to 5.0–39%, respectively. The genotypic correlation coefficients between traits at Bole and Wenchi varied from 0.33–0.98 to 0.07–0.77 respectively. Based on survival and precocity traits at Bole, the top five best-performing clones were BAMBOI7, BAME7, IDDM29, KT4, and KT5 collected from farmer’s fields. The identified clones constitute a suitable genetic resource pool for breeding resilient cashew varieties to increase production.