High-throughput phenotyping of an apple core collection: identification of genotypes with high water use efficiency

To detect genotypes with high water use efficiency (WUE) in apple (Malus x domestica), 193 genotypes from an INRA core collection were evaluated in 2014. Eight grafted replicates per genotype grown as one-year-old scions were studied in a high-throughput phenotyping platform (PhenoArch). Individual pot weight was recorded twice a day and irrigation was scheduled for 46 days according to two irrigation treatments: well-watered (WW), maintaining soil water content (SWC) at 1.4 g g(-1); and water stress (WS), reducing SWC until 0.7 g g(-1) and maintaining this value for ten days. For each genotype, half of the replicates were WW while the other half were grown under WS. Plant 3D images were automatically acquired every two days. Analysis of images and pot weight differences allowed the estimation of the accumulated whole-plant biomass (A_Bio) and transpiration (Plant_T) during the experiment. WUE was calculated as the ratio A_Bio/Plant_T. A_Bio and WUE had a higher genetic variation than Plant_T under WW and WS conditions. The genetic variation in WUE is a promising result, indicating that available genetic resources such as the INRA core collection could be useful to improve apple plant material for the use of water. WS reduced A_Bio and Plant_T but the reduction was less evident in WUE. Some genotypes had similar WUE values under WW and WS conditions. We identified of a group of 38 genotypes with high WUE under WW and WS. The existence of genotypes with high WUE whatever the water regime in apple may encourage apple breeders to consider the use of these genotypes as potential parents for improving apple plant material for the use of water.