Reproductive biology of Plukenetia corniculata Sm. (Euphorbiaceae), a traditional wild vegetable in Southeast Asia

Plukenetia corniculata Sm. is a traditional wild vegetable in Southeast Asia. However, its wild resources are becoming rare due to habitat destruction. To conserve and utilize P. corniculata resources, the knowledge of its reproductive biology is essential. In this study, the flowering and fruiting phenology, floral characteristics, breeding system, and seed characteristics of P. corniculata were systematically investigated. The results revealed that P. corniculata only needed approximately 5 months from sowing to fruit ripening. On average, the anthesis of a single pistillate flower, a staminate flower, and an inflorescence lasted approximately 10.50 days, 9.44 h, and 26.57 days, respectively. The stigma receptivity reached its peak on the sixth day after stigma dehiscence, while the pollen viability reached a maximum (73.58%) at the fourth hour after the staminate flower blooming. The estimated values of pollen-ovule ratio and outcrossing index, as well as the results of the artificial pollination experiments, suggested the breeding system of P. corniculata was classified as facultative xenogamy with self-compatibility. Additionally, the high kernel percentage (70.67%) and kernel oil ratio (58.65%) in P. corniculata seeds indicated its potential value for breeding. This study not only provides novel information on reproductive characteristics and optimal timing for artificial pollination of P. corniculata but also serves as a valuable reference for research on the reproductive biology of other Plukenetia species.