Fast-Tracking Yam Genetic Improvement Using High Ratio Propagation Technologies

Genetic improvement of yam is slow due to slow conventional hybridization, worsened by slow vegetative propagation, with one selection cycle per year. In the current informal seed system, uncertified seed yam is used in production and breeding, which may harbor contaminants, distorting research results. Protocols were developed for rapid production of quality propagules and for generating new variations. Meristems were excised from aseptic, virus-infected, in vitro shoots incubated at 37°C for 21 days and cultured on modified MS medium. Regenerated plantlets were virus-tested using multiplex PCR. Clean materials were introduced into Temporary Immersion Bioreactor. Endosperm from zygotic seeds of two genotypes were used for callus induction and plantlet regeneration in modified MS medium in a CRD. Oil immersion light microscope was used to count the chromosome of the roots formed by the regenerated plantlet, callus and their mother plants. Plants were cleaned from Yam mosaic and Yam mild mosaic viruses, 84 and 100% of the time respectively. In a 56-day cycle, 8 and 14 nodes were produced from 1 initial node for TDr 95/19158 and TDa 98/01167 respectively. One plantlet introduced to aeroponics can yield 300 rooted vine seedling in 1 year, much higher than a 1:6 ratio of the conventional minisett technique. Root from TDr95/18544 was pentaploid while the mother plant was tetraploid. The callus, plantlet and mother plant of TDr97/00917 were consistently tetraploid (4x). These ploidy variations can be exploited as new genotypes while rapid propagation technologies for quality seed yam will provide sufficient materials for multi-environment trials.