Variability Study on Nut Size and Number Trade-Off Identify a Threshold Level for Optimum Yield in Cashew (Anacardium occidentale L.)

Abstract

Eleven yield-related plant traits in 33 accessions selected from 3 Nigerian breeding populations were studied to understand the influence of nut size-number trade-off in cashew tree yield. Three-years of data were statistically analyzed for genetic variability estimates and showed that the accessions were significantly different for all the yield-related traits with highest variability in production of hermaphrodite flowers. The pattern of variation was population-specific with sparsely fruiting Brazilian accessions characterized by large nuts and kernels, while the Indian accessions were prolific but with small–medium nuts. Flowering, fruit-set, and fruit-development differed significantly between years suggesting a strong influence of environment on cashew tree production. Consistent relationships were found between nut number and total nut yield at both inter- and intra-population levels, underscoring the importance of the number to nut yield in cashew. However, regression between nut number and nut size confirmed the existence of the size-number trade-off phenomenon in cashew, but the degree varied between populations. Cashew trees with jumbo nuts (>15 kg) were significantly affected by the trade-off, as they exhibited poor flowering and fruit set, in addition to prolonged fruit development. This category of nut size should be discouraged for commercial planting. These preliminary results showed that cashew cultivars with nut sizes between 9.0 and 12.0 g are better, as such trees produced enough nuts per tree to support profitable investments in cashew farming.