Selecting key traits to indicrectly assess common bean growth under water stress

Abstract

Recognize water stress constraints on common bean growth may help to select tolerant genotypes, manage irrigation based on plant necessity and predict losses. This manuscript aims to select key traits that discriminate magnitudes of water stress on common bean and indicates plant growth constrains. To do so, an experiment was set in a greenhouse with two factors: crop evapotranspiration replenishment and cultivars. First factor was comprised of 25, 50, 75, 100, 125 and 150% of crop evapotranspiration replenishment starting at flowering (32 days after germination). The second factor was composed of the cultivars BRS Estilo and IPR Campos Gerais. A randomized block scheme with five replications was used, totalizing 60 experimental units. On the 55^th day after germination, we analysed morphological (steam diameter, leaf area, and number of trifoliolates) and physiological (net assimilation of CO₂, stomatal conductance, leaf transpiration, and total content of chlorophyll) traits. A multivariate analysis of variance indicated a single effect of crop evapotranspiration replenishment. Thus, a canonical discriminant analysis was applied and the discrimination was confirmed by the Scott-Knott hierarchical clustering. We harvested the plants to correlate the selected traits with the aerial dry weight to determine its ability to assess plant growth indirectly. The traits related to leaf gas exchanges were the strongest discriminators of levels of water stress and showed a moderated correlation with common bean growth. For instance, by assessing the net assimilation of CO₂ throughout the most stressful periods of the day, such a response variable turned out to be the most promising trait to be used in order to singly integrate both objectives under scrutiny.