Quantifying physiological determinants of potential yield in mungbean (Vigna radiata (L.) Wilczek)

A comprehensive understanding of key drivers of grain yield is essential to identify opportunities to improve productivity in mungbean (Vigna radiata (L.) Wilczek). The objective of this study was to assess and quantify physiological factors underpinning yield of mungbean grown in non-water-limiting conditions. Two field experiments, employing three genotypes (Jade-AU, Opal-AU and Satin II) and four canopy density treatments were conducted in the summer growing season (Jan-Mar) of 2019 and 2020 at Gatton campus, The University of Queensland, Australia. Crop leaf area dynamics, radiation interception, extinction coefficient (k), radiation use efficiency (RUE), total dry matter (TDM) (above ground dry matter) and grain yield (GY) were measured. Leaf area index (LAI), influenced by the canopy density treatments, was the key driver of differences in radiation interception. The variation in intercepted radiation resulted in differences in TDM and GY across canopy density treatments. Genotypes did not differ significantly and partitioned more than 90% of TDM to pod development. The radiation extinction coefficient, k, was stable and estimated to be 0.68, while average RUE was calculated as 1.3 g MJ-1. Variations in GY were strongly associated with grain number, which was related to intercepted radiation per unit of accumulated temperature around flowering. Using this quantification of the physiology of crop growth and yield in mungbean to form a simple crop model, simulations suggested that median potential yields of 1.88–2.48 tonnes ha−1 were possible in NE Australian production environments, with greater yield associated with spring sowing. Understanding the physiological basis of the very low RUE in mungbean was considered a key avenue to improve potential yield. This study has provided a quantitative framework for potential yield that will enable more comprehensive modelling of crop adaptation in mungbean.