Cytogenetic analysis of putative castor and cassava hybrids

Introgression of useful genes from related species is desirable in any breeding program. We studied the crossability, hybridity and possible introgression of useful genes in crosses made between cassava and castor. Sixteen putative hybrids were confirmed through cytology out of the putative hybrids and those that showed meiotic disruptions were identified. Most of the putative hybrids which were confirmed as hybrids by molecular techniques, had chromosome number 2n=2x=36. HY19, HY52, HY23 and HY63 had 2n+1 and 2n+2 in some cells and are therefore suspected to be aneuploids. Metaphase I chromosomes in these hybrids associated mostly as bivalents and there were more rings than rods. Pollen stainability of the putative hybrids ranged from 35.5 to 99.7%. Morphologically, most of the hybrids resembled cassava. This served as a first step in pursuing the introgression of useful genes from castor to cassava. Effort is being geared towards identifying the new genes. If the gene of an important trait such as the one responsible for the oil content of castor, for instance is eventually introgressed and harnessed, it could help to improve the oil that can be obtainable from cassava seed.