Evaluation of Water Use Efficiency in Mungbean using the Inverted-Bottle Pot System

Mungbean (Vigna radiata (L.) Wilczek) is a short-duration legume crop that is valuable for crop rotation. However, its yield potential is often limited by the water availability. Improving water use efficiency (WUE) in mungbean could increase mungbean production in water-limiting areas. Identifying genetic variability in mungbean for WUE is the first step to improving WUE and requires a fast and reliable screening method. This study evaluated twelve mungbean genotypes for WUE using Hunter’s inverted water bottle pot system (IBP) on two potting media (a potting mix of composting pine bark [UQ23] and Gatton vertosol soil). Morphology, agronomy, and physiology traits were measured and recorded, including six WUE traits. These WUE traits comprised a combination of two types of WUE (above-ground dry matter [WUEbio] and seed weight [WUEyield]) and three water consumption (total, before flowering, and after flowering [post]). Despite the difference in magnitude where plants in UQ23 used more water than in soil, the pattern of weekly water consumption was similar between these two potting media. The difference in water consumption among genotypes was observed after 46 DAS, and the peak water consumption occurred around flowering time (around 60 DAS). The variability due to the genotype-by-media interaction was very small (<10%) for most traits. The total and after-flowering WUE had large genotypic variance (>50%), similar heritability (0.6 for WUEbio and 0.8 for WUEyield), and strongly correlated ( The ranking of genotypes based on total WUE and after-flowering WUE was reasonably similar across the two potting media. However, the ranking based on WUEyield could differ from the ones based on WUEbio. Top genotypes in WUEyield (e.g., Berken) were only ranked in the middle in WUEbio, while top genotypes in WUEbio (e.g., King) were ranked lower in WUEyield. These results indicated that the size of the plants does not always correspond to seed weight. Therefore, WUEyield would be a better target trait than WUEbio to improve yield in mungbean. This study demonstrated the use of the IBP system to detect genotypic variability in WUE among mungbean genotypes under non-limiting water conditions for screening after-flowering WUE in mungbean.