Variation between short-duration mungbean cultivars (Vigna radiata (L.) Wilczek) in response to temperature and photoperiod

In this study, 14 cultivars of mungbean of reputed early maturity and high yield were examined in glasshouses for their responses to photoperiod and temperature. Photoperiods used were 12, 13, 14, 15 or 16h while the temperature regimes had 24h means of 18°, 21°, 24°, 27°, 30° and 33°; the day/night temperature differential in each case was 5°C. All cultivars flowered earlier with shorter days but Berken, T44 and T1 were close to day-neutral having a range of one week in flowering time across the photoperiods used. When the mean temperature was 24°C and the day length was 12 to 13h all cultivars flowered within 45 days from planting. However, there were indications of interactions between temperature and photopsriod; under a 16h photo-period all cultivars flowered when the mean temperature was 18° or 21 °C, but some cultivars were progressively delayed with further increase in temperature and failed to flower at the highest temperatures.

Of those cultivars which flowered under all conditions, seed yields per plant were generally greatest when mean temperature was around 24°C although a number of cultivars had their greatest yields at 21°C while two, namely S8 and S9, had a broad yield plateau from 18° to 27°C. Attention is drawn to the relative stability of the yield components, weight per seed and seeds per pod, and the use of this stability in breeding programmes is considered.