Standard Operating Procedure (SOP) for Ploidy Analysis in Banana

Banana is a natural multi-ploid crop. Wild bananas are seeded diploids (2x), while banana cultivars are seedless, mostly triploid (3x) and sometimes diploid. Because of the sterility of triploid bananas, improvement entails the generation of tetraploid intermediate hybrids (4x) which are fertile. Therefore, the determination of ploidy level is important for informative use and management of banana germplasm for different breeding objectives and targets. It guides the breeder on the choice of parents to include in a breeding scheme on the basis of ploidy among other considerations. Upon hybridization, bananas produce hybrids of mixed ploidy levels such as diploids, triploids and tetraploids. So it is very important to determine their ploidy level along with their performance in field trials so that hybrids are compared within their ploidy levels. Ploidy analysis happens at all stages of banana improvement, either on the products of hybridization for pre-breeding and breeding (figure 1), or on any newly acquired germplasm from genebanks or other banana breeding programs.