Expression of qualitative and quantitative traits in hybrids between domesticated and wild accessions of the tropical tuberous legume Vigna vexillata (L.) A. Rich.

Abstract

The expression of morphological, phenological and agronomic traits was recorded in parents and progeny of hybrids between domesticated and wild accessions of the tropical tuberous legume Vigna vexillata (L.) A. Rich. Generally similar patterns were observed in hybrid populations between the putative domesticate var. macrosperma and wild Australian and African accessions, and between a cultivated Bali variety and a wild Australian accession, although observations in the latter populations were severely constrained by genetic incompatibilities between the parents. Several traits of domestication, including broad leaflet size, ovate leaflet shape, non-pigmented stems, non-dehiscent pods, uniform seed testa colour and green seed testa were recessive to the wild type traits and under simple genetic control, with genetic linkages evident between several wild type traits. Most morphological and phenological traits were under quantitative genetic control with high to very high broad sense heritability and moderate to very high narrow sense heritability, indicating good prospects for advance through breeding and selection. An exception was time to flowering, where there were discontinuities in frequency distributions of F2 and backcross populations, with some apparent dominance for earliness over lateness. Another exception was the number of seeds per pod, which in the var. macrosperma × wild populations, appeared to be under qualitative di-allelic control, with homozygous plants having nearly twice the number of seeds per pod as heterozygous plants. In some populations, there was apparent hybrid vigour for vegetative growth and tuber size attributes. It was concluded that the wild African and Australian accessions could be used along with var. macrosperma for breeding improved varieties of V. vexillata for forage, cover crop and vegetable uses. However, for improved pod and seed attributes, particularly the yield, size and appearance of seeds, emphasis needs to be placed on sourcing greater genetic diversity within var. macrosperma and within the cultivated Bali variety, which, because of their genetic incompatibility, will need to be the focus of separate breeding programs.