CULTIVAR DIFFERENCES IN LEAF PHOTOSYNTHESIS AND GRAIN-YIELD OF WHEAT UNDER SOIL-WATER DEFICIT CONDITIONS

Cultivar differences in leaf photosynthesis (LPS) and grain yield of w heat [Triticum aestivum L.] were examined under irrigated and non-irri gated conditions in Cerrados, a semi arid region in Brazil. Twelve Bra zilian, five Mexican and two Japanese cultivars were used in this proj ect. The plants were grown under low planting density to elucidate the relationship between LPS and the potential yield of an individual pla nt. Brazilian cultivars ranked high in LPS, followed by Mexican and Ja panese cultivars under non-irrigated conditions, although there were p ractically no differences in LPS among these three groups of cultivars in irrigated conditions. The LPS showed a significant positive correl ation with grain yield (r = 0.63*) and dry matter yield (r=0.73**) pe r plant in non-irrigated conditions. However, LPS showed neither corre lation with grain yield nor dry matter yield per plant in irrigated co nditions. The present results suggests that PLS could be a breeding cr iteria to increase the yield per plant under soil water deficit condit ions.