Selection of barley lines for drought tolerance in low-rainfall areas

An experiment was conducted at five locations in Jordan (Khanasri, annual r ainfall 150 mm; Ramtha, 225 mm; Muwaqar, 150 mm; Rabba, 350 mm; Ghweer, 250 mm) during the 1996/1997 growing season, to evaluate the yield performance and some agronomic traits of 84 barley breeding lines and three long-term checks (Zanbaka, Arta and Klaxon) for drought tolerance. An a-lattice desig n with two replications and six incomplete blocks for each replication was used. Genotype 6 (WI2291/Tadmor) was found to be superior in grain yield, e specially compared to the best check (Arta) at the two wettest locations (R abba and Ghweer). Genotype 21 (Mo.B1337/WI2291/5//Emir/Sb//CM/67/3/F8-HB-85 4-23/121//148-221/4/CI08887/CI05761) out-yielded the best check (Arta) at t he driest location (Khanasri), while genotype 61 (Salmas/Arabia Aswad) prod uced a higher grain yield than the best check (Zanbaka) at Ramtha. The corr elations amongst grain yield, biological yield, straw yield, plant height a nd harvest index were always significant and positive regardless of the loc ation. The correlations amongst days to heading, days to maturity and grain yield were significant at the two driest locations only. This suggests tha t different phonologies an required to maximize grain yield in wet and dry environments. Also, the relationship between grain yield and the length of grain-filling period was positive in the wettest location (Rabba), negative in the driest (Khanasri) and not significant at the two intermediate locat ions. These results emphasize the importance of selection in the target env ironment and the need to develop early-maturing genotypes as a way of withs tanding drought and high temperatures during the grain-filling period. A hi gh and negative correlation coefficient was found between the drought susce ptibility index and grain yield at the driest site, whereas at the wettest site the correlation coefficient was lower and in some cases positive, indi cating the existence of traits that are desirable under drought and undesir able under favourable conditions.