Multi-trait selection index for high clonal cashew (Anacardium occidentally. L.) yield performance

The breeding of cashew varieties is expensive and time-consuming and the identification of a selection criterion that could rely on juvenile traits to effectively select for superior clones in later years of production could constitute a viable strategy to sustain production. We evaluated 20 cashew clones of varied origins over a 9 - year period under sub-optimal and near-optimal environment for growth and yield traits respectively. The trial was laid out in a randomized complete block design with four replications. There were significant clone × environment interaction effects for most traits. Under sub-optimal environment, high genotypic correlations were found between overall yield and survival, height, canopy volume, nut weight and the first 2-years, 3-years, 4-years, 5-years and 6-years of production whereas under near-optimal environment height, canopy volume, first 2-years, 3-years, 4-years, 5-years and 6 years of production years were high. Heritability ranged from 0.10–0.51, 0.11–0.52 and 0.20–0.74 for vegetative traits, nut quality traits and yield across years of production respectively. Under sub-optimal environment, selection for survival, height with rapidly expanding canopies and yield during the first 2 years of production were effective whereas under near-optimal environment selection for height with rapidly expanding canopies, shelling and yield during the first 2 years of production were effective. Our study suggest that the set of traits optimal for selection of high yield performers could vary with ecology and the identified criterion has a large potential to identify the most productive clones early in the cashew breeding program.