Heritability and genetic variation of plant biomass, transpiration, and water use efficiency for an apple core-collection

To study the heritability and genetic variation of plant biomass, transpiration and water use efficiency (WUE) in apple (Malus × domestica Borkh.), 193 genotypes from an INRA apple core-collection were evaluated in 2014. Four 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 to maintain constant soil water content (SWC) and avoid any water stress during 46 days. Plant 3D pictures were automatically taken every two days. Analysis of pictures and pot weights differences allowed the estimation of whole-plant biomass and transpiration during the experiment. WUE was calculated as the ratio of accumulated biomass to transpiration. For each trait, we tested nine mixed models to account for the genetic effect and spatial variability inside PhenoArch. The Best Linear Unbiased Predictors (BLUPs) of genetic values were estimated after model selection. For each trait, broad-sense heritability (H²) was calculated from variance estimates. Plant biomass, transpiration and WUE had H² values of 0.76, 0.54, and 0.73, respectively. The H² value of WUE is high enough to consider that this trait is under genetic control in apple. The genetic variation of WUE indicated that apple genetic resources such as the INRA core-collection could be extremely useful to improve apple plant material for the use of water.