In collaboration between VIB and the Meise Botanic Garden, we gathered information on the drought tolerance of beans, a crop representing the main component in the diet of millions of people worldwide. The partnership tested a collection of 185 accessions of Vigna and Phaseolus species for drought tolerance.  In order to perform a broad evaluation of drought tolerance, plant responses were quantified through a period of drought stress. Tolerance is most often evaluated in terms of yield or biomass under drought stress compared to a control group. A common challenge with this approach is that smaller plants generally show a smaller biomass reduction compared to their control group than large plants. One solution to this issue is to look at water use efficiency (WUE) instead of using absolute biomass or yield. WUE is the amount of biomass produced per unit of water used by the plant. Since lower growth rates are associated with a lower water consumption, WUE alleviates the bias towards smaller plants. Using parameters resulting from images taken with an RGB, multispectral and hyperspectral camera, 5 drought response indicators were derived:

• Biomass penalty
• Change in WUE under drought
• Soil moisture at leaf desiccation
• Soil moisture at chlorosis
• Root/shoot ratio