Agronomic studies on Vigna spp. in south-eastern Queensland. I. Phenological response of cultivars to sowing date

Abstract

Phenological development of 16 cultivars from four Vigna species (V. radiata, green gram; V. mungo, black gram; V. angularis, adzuki bean; V. umbellata, rice bean) was studied over a range of 17 weekly sowing dates at Lawes in south-eastern Queensland. Cultivar and sowing date effects on phenology were large. In all cultivars, the rate of development during pre-flowering was associated negatively with mean day length and positively with mean maximum and/or mean minimum temperature. Cultivars differed in sensitivity to both photoperiod and temperature. Genetic lateness of flowering among cultivars was associated positively with increasing sensitivity to day length and negatively with the latitude of cultivar source. In the grams, early-flowering cultivars showed response to maximum temperatures, while the later-flowering lines responded to minimum temperatures. Rate of development in all four species during the reproductive phase was largely independent of cultivar and sowing date, per se, but rather appeared to depend on the day length and temperature regimes prevailing subsequent to the onset of flowering. The reproductive period in all species was shortest for those cultivar x sowing date combinations which commenced flowering in early autumn. Where flowering occurred in midsummer, i.e. for early sowings and for early cultivars, the reproductive period was extended as a consequence of prolonged flowering in response to the longer prevailing day lengths. As the date of flowering was delayed into mid or late autumn, the reproductive phase was extended owing to slower pod maturation rates in response to cooler prevailing temperatures. The implications of these responses on adaptation and agronomic utilization of these species are discussed.