High-throughput phenotyping for the genetic dissection of drought tolerance related traits in Zea mays and Triticum durum Desf.

In this dissertation we expose the results of two research conducted using high-throughput phenotyping techniques with the aim of discovery the genetic bases underling drought adaptive traits in maize and durum wheat. In the first study, we used a maize Introgression Library (IL) derived from the cross between Gaspé Flint (an early flowering Canadian landrace) and B73 (an elite genetics reference line) which was previously shown to segregate for phenology and seminal root architecture (SRA). The IL was phenotypically evaluated in the high-throughput platform PhenoArch (INRA, Montpellier), for large-scale automated imagery and evapotranspiration measurements of potted plants in controlled environment, under well-watered and water-deficit conditions. Biomass accumulation for each plant was estimated by software and model-assisted imaging analysis. Several QTLs were detected (Dunnet test p-value < 0.05) for biomass accumulation and water-use efficiency (WUE) on chr. 1, 2, 3, 4, 7, 8, and 9). In the second study we report the characterization of 183 elite durum wheat (Triticum turgidum ssp. durum Desf.) for root system architecture (RSA) and shoot developmental traits. Plants were grown in the high-throughput phenotyping platform GROWSCREEN-Rhizo, a rhizo-box-based system. Seminal, nodal and lateral root length was measured twice per week. Measurements of leaf area, leaf number and tiller number were performed twice per week and SPAD measurements were collected twice during the experiment. A genome-wide association study (GWAS) identified many QTLs for RSA and/or shoot growth traits (P < 0.0001). GWAS confirmed a highly significant effect on adult plant root system width due to two major QTLs on chromosomes 6AL and 7AC. Notably, shoot/root ratio revealed a strong, contrasting selection pattern between the cultivars released by the rainfed and irrigated breeding programs conducted at ICARDA and CIMMYT, respectively, suggesting an indirect but major role of RSA features in durum wheat breeding and environmental adaptation.