Gamma irradiation coupled with in vitro technology was used to develop BBTV resistance in banana cv ‘Lakatan.’ Ten (10) resistant lines were selected after several generations of evaluation and selection. The selected lines (M1V3–M1V4) showed low disease incidence in the field under high disease pressure and, likewise, low disease incidence with aphid inoculation of the virus. Further disease evaluation (M1V4–M1V5) on these lines consistently showed low BBTV disease incidence (11.62–28.57%) 30 mo from planting (MAP). The genetic variability in morpho-agronomic traits derived from SHAN cluster analysis grouped the selected lines into four major clusters for qualitative traits at 0.636 coefficient of similarity and three clusters for quantitative traits at 0.11 Euclidian distance coefficient. Selections based on agronomic traits showed significantly earlier flowering in three mutant lines and shorter stature in two mutant lines. Short strand repeat (SSR) analysis using 11 primers detected a high level of polymorphism in mutant lines. Mutant lines were differentiated from the ‘Lakatan’ control by the absence of one or few alleles in mutant lines with four primers and/or addition of one or few alleles in mutant lines with two primers. SSR analysis revealed genetic differences among mutant lines and between mutant lines and ‘Lakatan' control. The results of the study further affirmed stable BBTV resistance in advanced generation evaluation (M1V4M1V5). Five out of ten resistant lines were selected for further evaluation in multi-location field trials as a requirement for registration and release of new BBTV resistant mutant variety of ‘Lakatan.’

The National Plant Genetic Resources Laboratory maintains the largest in vitro germplasm collection of Dioscorea in the Philippines and has remained steadfast in its aim to safeguard accessions with potential use. Due to costly and time-consuming operations, most gene banks operate with the guidance of diversity assessments to measure the genetic integrity of one’s collection and design appropriate protocols for conservation. Diversity assessment under in vitro conditions remains unexplored even with the advantages of increased security and functionality in limited spaces. This study aimed to assess the genetic diversity of the in vitro conservation response of yam germplasm collection of the country. Four Dioscorea species totaling 217 accessions were subjected to in vitro culture conditions. Parameters such as % surviving cultures, % shoot regeneration, and degree of tissue browning were analyzed using the Shannon-Weaver diversity index and cluster analysis. Assessment of initial culture establishment and regeneration responses revealed a high degree of variability. D. alata had the highest response in % surviving cultures and % shoot regeneration. Diversity analysis using the Shannon-Weaver index revealed high diversity among the species and differences in diversity within species. This high level of diversity can be attributed to the distribution of responses observed in the accessions of each species. This high genetic diversity observed in the in vitro cultured Dioscorea indicates the necessity for the development of several in vitro culture protocols to obtain optimum responses for regeneration, conservation, and other in vitro applications.