Rates of progress towards flowering and podding in bambara groundnut (Vigna subterranea) as a function of temperature and photoperiod

Abstract

The influence of temperature and photoperiod on phenological development of three bambara groundnut (Vigna subterranea) selections from Botswana; Zimbabwe and Mall was investigated in a semi-controlled environment experiment with factorial combinations of three constant temperatures (20.9, 23.4 and 26.2 c) and four constant photoperiods (10.0, 12.5, 13.5 and 16.0 h d-a). In all three selections, the onset of flowering was influenced by temperature but not by photoperiod, while the onset of pod-growth ('podding') of all three selections was influenced by both factors. The influence of temperature and photoperiod was quantified by means of photothermal models, linking development rates to temperature and photoperiod with linear equations. The rate of progress from sowing to flowering of the three selections could be described very well (r2 > 95 %) as a function of temperature; the rate of progress from flowering to podding was described reasonably well as a function of both temperature and photoperiod by a combination of one to three response planes (r2 for the different selections ranging from 63 to 90%). Model testing with independent data sets showed good agreement between observed and predicted times to flowering and podding.