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Classical breeding has had little impact due to the moderately long juvenile period and narrow genetic base (Nadagauda et al., 2005). Cashew breeding programmes are active in Brazil, Venezuela and India. The National Cashew Research Centre of India has eight regional research centres in cashew-growing states that focus on improved productivity of trees. Cashew is known to have an aggressive tap root and feeder root system (Nadagauda et al., 2005). Uniformity of rootstocks is not a major factor that affects production. The rootstocks are selected on the basis of their adaptation to local biotic and edaphic conditions. Root borer-infected cashew tree rootstocks cause c.40% tree loss within 2 years of infestation (Maruthadurai et al., 2012). Plocaederus ferrugineus L. is the most serious pest causing stem and root damage. Rootstocks resistant to the coleopteran, P. ferrugineus, are preferred. Other pests which act as secondary infestations are Plocaederus obesus Gahan and Batocera rufomaculata.

BREEDING ACCOMPLISHMENTS. Castro et al. (2011) reported 621 accessions of cashew in Brazil, most of which belong to A. occidentale. The accessions have desired traits such as dwarf growth, early flowering, bold nut size, higher kernel grade, large apple, resistance to or tolerance of cashew stem and root borer (CSRB) caused by P. ferrugineus and P. obesus, tea mosquito (Helopeltis spp.) and powdery mildew disease caused by Oidium anacardii Noack, abiotic stress, i.e. moisture, climate change, etc. In India, germplasm diversity is limited since it is an introduced crop. Breeding programmes have resulted in 42 cashew cultivars released by the Directorate of Cashew Research centres (Saroj, 2015), of which 29 are based on selections of seedling progeny and 13 obtained through selective hybridization by controlled pollination. Twenty-one of them have kernels of export grade (W180–W240), whereas others have higher quantities of CNSL, red colour of the apple, compact canopy density, etc. Nigerian cashew germplasm is mainly composed of exotic selections (Adebola and Esan, 2002); however, the novel trait of increased testa peelability of Nigerian cashew could improve its global competitiveness (Adeigbe et al., 2015).