Résumé
Promising agronomic crop traits could be more accessible to breeding if we understood their underlying plant processes and knew their genetics determinacy. Here, we attempt to progress understanding of the functional linkages between traits using PCA and quantitative trait loci (QTL) co-localization approach. A recombinant inbred lines (RIL; 181 progenies) population derived from a cross between senescent (N13) and stay-green(E36-1) parental lines was selected. This population was previously shown to segregate for stay-green expression and Striga resistance in the field. Here it was phenotyped for: (i) grain size variability under optimal field conditions; (ii) traits related to early-vigor (canopy size and growth rate) in a high-throughput phenotyping platform. Most traits had high heritability (>60%). Linkage map was constructed (271 molecular markers) and QTL analysis (Cartographer 2.5) performed using composite interval mapping function. Two major QTLs influencing canopy size were found on SBI04 and SBI05. The SBI05 QTL harboring canopy size co-localized with the grain size QTL and with the genetic region of stg-4 (stay green) QTL (responsible for leaf size distribution). This links the vigor traits to the variability in grain size and leaf development (i.e. stay-green mechanism) the latter possibly explaining the variability in grain size. Since grain size partially regulates grain nutrients profile, such linkage calls for further exploration in breeding. The SBI-04 QTL for canopy size co-localized with QTLs for Striga resistance, strengthening the hypothesis that plant vigor enhances Striga resistance. Vigor appears to explain several traits and could be rapidly screened at the LeasyScan facility.