SELECTION CRITERIA FOR COMBINING HIGH GRAIN-YIELD AND HIGH GRAIN PROTEIN-CONCENTRATION IN BREAD WHEAT

This study was designed to identify selection criteria for the simulta neous improvement of grain yield and grain protein concentration in sp ring wheat (Triticum aestivum L.). Eight cultivars were selected. Six expressed contrasting levels of grain protein concentration and grain yield. Two, the cultivars 'UM632' and 'UM684', expressed high levels o f both traits concurrently. Plants in replicated plots were sampled fr om anthesis to maturity over 2 yr and data were collected on traits re lated to nitrogen N and dry matter accumulation and remobilization. Gr ain protein concentration was not correlated with grain yield but was correlated with post-anthesis N uptake (r = 0.66*), total plant N at maturity (r = 0.49*), and N harvest index (r = 0.87**), and was inver sely correlated with vegetative N at maturity (r = -0.49*). Grain yie ld was correlated with both post-anthesis N (r = 0.50*) and dry matte r uptake (r = 0.58*), with total N (r = 0.78**) and dry matter (r = 0 .77*) at maturity, and with harvest index (r = 0.83**), Grain protein yield was highly correlated with post-anthesis N accumulation (r = 0. 90*), total N at maturity (r = 0.98**) and the sum of N harvest index and harvest index (r = 0.93*). UM632 and UM684 coupled high post-ant hesis N uptake and total N at maturity with high remobilization effici ency and N harvest index, while maintaining harvest index. We conclude d that grain protein concentration and grain yield could be improved s imultaneously if selection was practiced for threshold levels of grain yield or protein concentration followed by selection for grain protei n yield in populations constructed from crosses combining high total N at maturity, N harvest index and harvest index.