Post-flowering photoperiodic and temperature effects on phonological development and yield in field-grown bambara groundnut (Vigna subterranea) landraces in a sub-tropical environment.

Abstract

The post-flowering phonological development of two local bambara groundnut (K/gna subterranea) landraces was studied at Luyengo, Swaziland using six sowing dates between mid-October 1999 and late January, 2000. The objective was to examine the influence of variation in post-flowering photoperiod and temperature on the phonological development and pod yield of the crop. While the rate of progress from sowing to podding was influenced by both temperature and photoperiod, the rate of progress from flowering to podding (1/ (p-f), with (p-f) being the number of days from 50% flowering to 50% podding) was influenced only by photoperiod between flowering and podding (r = 0.86, p < 0.01). Pod yield was strongly and positively related to the duration of the pod­ filling period (r2 = 0.96, p < 0.01), while the duration of the pod-filling period was strongly related to thermal time accumulated during the reproductive period. Photopcriod during the reproductive period influenced pod yield indirectly, through its influence on the onset of podding. The study confirms the photosensitivity of the onset of podding in bambara groundnut, and it was concluded that in bambara groundnut, unlike in other leguminous crops, the duration of the reproductive or pod-filling period, and therefore yield, are largely influenced by environmental factors prevailing at and subsequent to the onset of flowering.