Grain filling parameters of two- and six-rowed barley genotypes in terminal drought conditions

After the kernel number per spike has been formed during the vegetative stage, grain weight depends on the rate and duration of grain filling. Drought and high temperatures during the grain filling stage frequently occurs in the majority of barley growing regions worldwide. To investigate impact of terminal drought stress on grain filling parameters and grain yield, 15 two- and 10 six-rowed barley genotypes were tested in two-year field trials, set in two locations with two treatments. One treatment was control (C), while in the other treatment (D) terminal drought was simulated by mechanical removal of all leaf blades 7 days after heading of each genotype. In average, defoliation caused reduction of yield (33%), grain filling rate (12%) and 1000-kernel weight (11%). In both treatments, grain yield and the absolute grain filling rate were higher in two-rowed barley genotypes than in six-rowed ones. In both treatments, the correlation was stronger between yield and grain filling duration than between yield and the grain filling rate. The correlation between average yield and grain filling duration was stronger in the D than in the C treatment. According to the results obtained for terminal drought conditions, breeders should create early maturing genotypes of two-rowed type, with a longer grain filling duration and the gradual accumulation of dry matter.