Genetic analysis of plant water status and osmotic adjustment in recombinant inbred lines of sunflower under two water treatments
Résumé
The goals of the present research were to develop an integrated and high density genetic-linkage map using simple sequence repeat (SSR) and amplified fragment length polymorphism (AFLP) markers on a population of 123 F9 recombinant inbred lines (RILs) and to identify QTLs involved in the genetic control of water status traits and osmotic adjustment under well-watered and water-stressed conditions. A map with 304 AFLP and 191 SSR markers with a mean density of one marker per 3.7 cM was constructed. Our physiological experiment consisted of a split-plot design with three blocks. The main plot consisted of water treatments (well-watered and water-stressed) and subplot contained 78 RILs and parental lines. Water deficit was induced in 45-day-old plants at stage near flower bud formation for a period of 12 days. After 12 days of differential watering, water status traits (leaf water potential, relative water content, turgor potential, osmotic potential and osmotic potential at full turgor) as well as osmotic adjustment (OA) were evaluated. The effects of water treatment, RIL and ‘RIL × water treatment’ were significant. QTL analysis showed that several putative genomic regions are involved in the total variation of water status traits under two water treatments. Among 24 QTLs detected under well-watered conditions, 5 (about 21%) were also detected in the water-stressed treatment. The percentage of phenotypic variance explained by the QTLs ranged from 6% to 29%. Among the eight QTLs detected for OA, four of them (50%) were co-located with the QTLs for turgor potential (Ψt) on linkage group 4 (OA.4.1), with the QTL for osmotic potential at full turgor (ΨsFT) in well-watered RILs on linkage group 12 (OA.12.2), and with QTLs of several traits on linkage group 5 (OA.5.1 and OA.5.2). The four other QTLs for OA (50%) were very specific. The major QTL for OA on linkage group 5 accounted for 29% of the phenotypic variation, which is overlapped also with the QTLs for several water status traits. However, the QTLs were identified in greenhouse conditions and the usefulness of these QTLs for marker-assisted selection should therefore be evaluated under field conditions, and validated in other genetic backgrounds.