Chromosome studies in Cashew (Anacardium occidentale L.)

Despite the increased cultivation of cashew as a commodity crop in sub-Sahara Africa, Asia and South America there are few chromosome studies on it. The present study investigates number, structure and behavior of chromosome in cashew populations growing in Nigeria. Cytological examination of these populations revealed a diploid and haploid chromosomes of 2n = 42 and n = 21 respectively. The karyotypes were mostly symmetric, composed mainly of metacentric pairs and several submetacentrics. Similarity in the morphology, number and behavior of the chromosomes in the accessions from different populations or origin attests to the degree of genetic closeness of the selections. This probably indicates high potential for use as parents in the breeding and improvement of cashew with very limited cross-incompatibility barriers (free gene exchange). Polymorphism in chromosome number was not recorded among these cashew selections.