Model-Assisted Estimation of the Genetic Variability in Physiological Parameters Related to XXXX Fruit Growth under Contrasted Water Conditions.

@entity71 @entity51 @entity523 @entity505 @entity393 @entity3363
UNASSIGNED: Drought stress is a major abiotic stress threatening plant and crop productivity. In case of fleshy fruits, understanding mechanisms governing water and @entity505 accumulations and identifying genes, QTLs and phenotypes, that will enable trade-offs between fruit growth and quality under @entity51 ( @entity51 ) condition is a crucial challenge for breeders and growers. In the present work, 117 recombinant inbred lines of a population of @entity523 were phenotyped under control and @entity51 conditions. Plant water status, fruit growth and composition were measured and data were used to calibrate a process-based model describing water and @entity505 fluxes in a growing fruit as a function of plant and environment. Eight genotype-dependent model parameters were estimated using a multiobjective evolutionary algorithm in order to minimize the prediction errors of fruit dry and fresh mass throughout fruit development. @entity51 increased the fruit dry matter content (up to 85%) and decreased its fresh weight (up to 60%), big fruit size genotypes being the most sensitive. The mean normalized root mean squared errors of the predictions ranged between 16-18% in the population. Variability in model genotypic parameters allowed us to explore diverse genetic strategies in response to @entity51 . An interesting group of genotypes could be discriminated in which (i) the low loss of fresh mass under @entity51 was associated with high active uptake of @entity3363 and low value of the maximum cell wall extensibility, and (ii) the high dry matter content in control treatment (C) was associated with a slow decrease of mass flow. Using 501 SNP markers genotyped across the genome, a QTL analysis of model parameters allowed to detect three main QTLs related to xylem and phloem conductivities, on chromosomes 2, 4, and 8. The model was then applied to design ideotypes with high dry matter content in C condition and low fresh @entity393 in @entity71 . The ideotypes outperformed the RILs especially for large and medium fruit-size genotypes, by combining high pedicel conductance and high active uptake of @entity3363 . Interestingly, five small fruit-size RILs were close to the selected ideotypes, and likely bear interesting traits and alleles for adaptation to @entity51 .
