RELATIONSHIP BETWEEN CARBON-ISOTOPE DISCRIMINATION AND GRAIN-YIELD INSPRING BARLEY UNDER DROUGHT CONDITIONS

The correlation between water use efficiency (WUE) and carbon isotope discrimination of C3 photosynthesis has been reported by various autho rs. On the basis of these data, we were expecting that the WUE affects grain yield during drought conditions. To test our hypothesis, we hav e collected samples of 110 spring barley varieties and breeding lines in stage 'Feekes 16' during the year 1989. This year was characterized by extremely low precipitation. The ratio of carbon isotopes C-12 and C-13 determined as deltaC-13-values and the grain yield was measured. The correlation coefficient obtained for these two parameters was sma ll (r = 0.226) but significant. Methodically perhaps the determination of deltaC-13 values could be helpful in breeding for an improved wate r use efficiency.