RELATIONSHIPS BETWEEN RELATIVE WATER-CONTENT AND GROWTH-PARAMETERS UNDER WATER-STRESS IN BARLEY - A QTL STUDY

Drought strongly affects cereal yield in several regions of the world. Plant growth and plant water status in response to soil water deficit play an important role in tolerance to drought and in yield stability . In order to investigate the relationship between plant growth and wa ter relations, 187 barley (Hordeum vulgare L.) recombinant inbred line s from a cross between two Mediterranean varieties, Tadmor and Er/Apm, were studied in a growth chamber for RWC, number of leaves on the mai n tiller (NL), number of tillers (WT) and total shoot fresh and dry bi omass (TSFM and TSDM). Measurements were made at the beginning of till ering on well watered plants and at a soil moisture content of 14% of field capacity. A negative phenotypic correlation between RWC and grow th parameters was obtained in both treatments. Under water stress, a n egative genetic correlation was also found between the same characters . QTLs involved in RWC, NL and TSFM variation were positioned on a RFL P-RAPD genetic map. Different DNA regions involved in constitutive and water stress responses were detected. In the stress treatment, one re gion on chromosome 1 was involved in RWC and NL variation giving a gen etic basis to the phenotypic correlations found. Separated map positio ns were also found for RWC and NL. Epistatic interactions between seve ral QTLs and between QTLs and other markers were detected only in the water stress treatment, suggesting that some chromosomal regions might be involved in the regulation of the expression of the traits under w ater stress. This work suggested that even if some parameters are stro ngly correlated, finding QTLs for only one trait is not sufficient to detect all the candidate regions which might be involved in the contro l of the correlated traits. The results of localization and co-localiz ation of QTLs are physiologically interpreted.