New QTLs identified for plant water status, water-soluble carbohydrate and osmotic adjustment in a barley population grown in a growth-chamber under two water regimes

Quantitative trait locus (QTL) analysis was carried out with 167 recombinant inbred lines (RILs) of barley derived from a cross between Tadmor and Er/Apm to identify the genomic regions controlling traits related to plant water status and osmotic adjustment (OA). The experiment was conducted in a growth chamber using a random incomplete block design (nine blocks). Relative water content (RWC) and leaf osmotic potential (psi (pi)) were measured at 100% and 14% of the field capacity on 105 RILs in each block. In addition, the water-soluble carbohydrate concentration (WSC) was measured in the four first-blocks. The leaf osmotic potential at full turgor (psi (pi)100), the water-soluble carbohydrate concentration at full turgor (WSC100), and also OA, the accumulation of water-soluble carbohydrates (dWSC100), the contribution of a change in water content to OA (CWC) and of the net solute accumulation to OA (SA) have also been calculated. In a previous paper (Teulat et al. 1998), 12 QTLs were identified for RWC, psi (pi), psi (pi)100 and OA with adjusted means (block effects and pot-within-block effects fixed) with an incomplete genetic map. In the present paper, a more-saturated and improved map is described. A new QTL analysis as been performed with adjusted means. The new QTLs identified for previous evaluated traits, as well as the QTLs for the new traits, are presented. Eight additional regions (22 QTLs) were identified which increased to 13 the total number of chromosomal regions (32 QTLs) controlling traits related to plant water status and/or osmotic adjustment in this barley genetic background. The results emphasise the value of the experimental design employed for the evaluation of traits difficult to assess in genetic studies. The putative target regions for drought-tolerance improvement are discussed combining arguments on the consistency of QTLs and, when possible, the physiological value of QTLs (trait relevance, syntenic relationships and clustering of QTLs).