Genetic compatibility among domesticated and wild accessions of the tropical tuberous legume Vigna vexillata (L.) A. Rich.

Abstract

Phenotypic similarities and differences between a cultivated variety of the tuberous legume Vigna vexillata from Bali, Indonesia, the putative domesticated variety macrosperma and wild types from Africa, Australia and Indonesia, were reported previously. The present study was undertaken to establish the genetic compatibility of these three accession classes. Seventeen accessions, comprising eight cultivated Bali accessions, one var. macrosperma accession and eight wild accessions from Africa and Austronesia, were grown in large pots in shade house facilities in Townsville, Australia. Not all hybrid combinations were attempted because for some accession combinations, suitable matching flowers were not available at the same time. The main aim was to attempt enough crosses between accessions from the respective classes to establish whether the classes were genetically compatible. Hybridisation was conducted by hand pollination in the morning, using newly-open flowers that had been emasculated before sunset on the day before. Pods and viable hybrid seed were obtained from the Bali × Bali, var. macrosperma × wild and wild African × wild Austronesian combinations. However, difficulty was encountered in obtaining viable and/or self-fertile hybrids between the Bali accessions and the other two classes. Depending on the particular combination of parental accessions, different genetic breakdown mechanisms were observed with the Bali × var. macrosperma and Bali × wild combinations. In some instances, flowers failed to set pods and/or the young pods abscised before maturity; pods set but seed were shrivelled and/or non-viable; viable seeds were set but the hybrid seedling plants were short-lived; or, in a few instances (Jimbaran Bali × wild Austronesian), vigorous hybrid plants were obtained but were self-sterile. Mitotic chromosome counts showed there was no difference in chromosome number between the Bali accessions, the Austronesian accessions and those hybrids that were viable but infertile. All exhibited 2n = 22. Pollen viability analyses using Alexander’s stain indicated that the numbers of pollen grains per flower and the percentages of pollen grain that were viable were substantially lower in the hybrids than in both the cultivated Bali and wild parental accessions. Consistent with this observation, small numbers of viable seeds were obtained when viable pollen from the respective parents was backcrossed onto the self-sterile hybrids. The results suggested that the cultivated Bali accessions do not belong to the same primary gene pool as the other cultivated and wild V. vexillata accessions and that it would be difficult to use the Bali accessions and var. macrosperma concurrently to breed seed crop varieties. A taxonomic review of V. vexillata is also warranted.

QTL Analysis of Domestication Syndrome in Zombi Pea (Vigna vexillata), an Underutilized Legume Crop

“…However, in our present study, we successfully obtained an F 2 population from a partially fertile F 1 hybrid of a cross between the cultivated zombi pea from Bali using the former as female parent and wild zombi pea, this suggested that the Bali cultivated zombi pea constitutes a primary gene pool with the wild zombi pea. The difference results in our study and that in Damayanti et al [8] is possibly due to environmental factors. Damayanti et al [8] noted that even self-pollination of the cultivated zombi pea from Bali results in low pod setting.…”

“…A previous study on reproductive compatibility among cultivated zombi pea from Bali (tuber type zombi pea),cultivated zombi pea from Africa (seed type zombi pea), and wild zombi pea from Africa and Australia revealed no productive incompatibility between the African cultivated zombi pea (seed type zombi pea) and the wild form from both Africa and Australia, but revealed various pre- and post-zygotic compatibilities between the Bali cultivated zombi pea (seed type zombi pea) and the wild form from Africa and Australia [8]. However, in our present study, we successfully obtained an F 2 population from a partially fertile F 1 hybrid of a cross between the cultivated zombi pea from Bali using the former as female parent and wild zombi pea, this suggested that the Bali cultivated zombi pea constitutes a primary gene pool with the wild zombi pea.…”

“…It has erect growth habit and large seed size, and is insensitive to day length and no seed dormancy with some degree of pod dehiscence. The variety macrosperma is highly cross-compatible with wild V. vexillata [8]. The tuber type zombi pea has not yet been classified as a variety of V. vexillata .…”

“…The tuber type is grown principally for fresh edible tuber roots which contain as high as 15% of proteins [5,6]. This cultivated type has been reported to be cross-incompatible with wild V. vexillata and the variety macrosperma [8]. The phenotypic difference between the two cultivated types of V. vexillata is a result of divergent selection during the evolution of the crop.…”

Genetic diversity and population structure of pencil yam (Vigna lanceolata) (Phaseoleae, Fabaceae), a wild herbaceous legume endemic to Australia, revealed by microsatellite markers

“…Nonetheless, the two genetic clusters detected in the current study suggest that V. lanceolata is a complex species comprising two closely related taxa or a single species with two different genepools/ population structures; the two taxa/genepools/populations may be related largely to the northern pubescent and var. lanceolata Damayanti et al 2010). The genetic structures reported in these Vigna species were associated with their geographical differences.…”