GENETIC-IMPROVEMENT EFFECTS ON PREANTHESIS PHYSIOLOGICAL ATTRIBUTES RELATED TO WHEAT GRAIN-YIELD

Changes in preanthesis physiological attributes related to genetic improvement for grain-yield were studied for six Argentinian bread-wheat (Triticum aestivum L.) cultivars released at different times between 1912 and 1980. Experiments were carried out in the field during 1986 and 1987. Biological yield at anthesis was not significantly correlated with year of release. Similarly, no evidence was found of changes in the proportion of photosynthetically active radiation (Qpa) intercepted at anthesis or the efficiency of conversion of intercepted radiation in net dry-matter production pre-anthesis. Biomass partitioning to the spike at anthesis was positively and significantly correlated with year of release of the cultivars. Both spike dry-weight at anthesis and the spike-dry-weight: above-ground-biomass ratio at anthesis were closely associated both with grains per m2 and with harvest index. These last-named characters best explained the changes in grain-yield. Thus, the changes in grain-yield and harvest index achieved by plant breeding could be due to parallel changes in spike dry-weight at anthesis and pre-anthesis biomass partitioning to the spike. © 1990.