Cashew nut (Anacardium occidentale l.) breeding strategies

Abstract

Cashew nut (Anacardium occidentale L.) is a tropical, cross-pollinating tree native to South America. Vietnam ranks first in global production of cashew nuts with shells. World average productivity stands at 8136 hg/ha, but in most cashew-growing countries production is below the world average. Low yield is because of lack of soil profile correction, irrigation and pest control and prevalence of orchards of trees grown from seed selections and grafted genotypes. The tree bears male (staminate and bisexual), hermaphrodite and pistillate flowers on the same panicle. Only, 4–6% of flowers are pollinated and reach maturity to bear fruit, the rest are shed away at various stages of development. Generally, the gene pool expands through hybridization with different adaptive values, as long as the hybrids are able to produce segregating progeny in subsequent generations. Evidence of hybrid vigor with an increase of up to 153% in nut yield has been noted as compared to plants derived from out-crossed pollination. Uniform planting materials is a very important input for crop productivity. Cashew improvement programs include development of new commercial varieties having dwarf/semi-dwarf canopy, large nut size with higher shelling percentage, higher kernel grade and tolerance to biotic and abiotic stresses. A hybridization method has been standardized for breeding cashew varieties. Technologies like molecular markers, mutation breeding, molecular breeding, in vitro approach and transgenic breeding and other techniques are expediting the process of analyzing and assessing traits. With the advancements in genetics and molecular biology, genetic engineering has become the primary issue in molecular breeding. The present chapter highlights the propagation methods, improvement through conventional breeding, molecular genetic diversity, molecular breeding and conservation strategies.