Genetic Variation for Nitrogen Assimilation and Translocation in Wheat. I. Dry Matter and Nitrogen Accumulation¹

Abstract

This study was conducted to provide basic information on the accumulation of dry matter and N in spring wheat ( Triticum aestivum L.) and to develop data necessary for an understanding of the physiological and genetic relationships between N movement and grain yield and protein concentration. ‘Anza’ and ‘Cajeme 71’ and 96 random F 4 and F 5 lines derived from the hybrid of these two cultivars were studied in field experiments at high and low N fertility regimes. Anza, the high yielding, low grain protein parent, continued to accumulate vegetative dry matter after anthesis, suggesting utilization of postanthesis photosynthates in grain filling. Anza also assimilated more N during the reproductive stage than Cajeme 71, the lower yielding, high protein parent.A considerable loss of vegetative dry matter between anthesis and maturity was observed in Cajeme 71 suggesting a greater reliance on photosynthates formed prior to anthesis for grain filling in this cultivar than in Anza. Significant but low negative correlations between yield and grain protein concentration for 96 F 5 lines indicated that simultaneous increases in grain yield and protein concentration could be achieved by selection. Grain yield was positively and grain protein concentration was negatively correlated with time of maturity. However, lines combining both high grain yield and high grain protein concentration (e.g., 8.4 Mg ha ‐1 , 14.8% protein) were identified over the range of maturity of the majority of lines. Genotypic variation among the F 5 lines was significant for all measured traits except one. In that exception total N yield at anthesis in the low N experiment did not show significant genotypic variation in the F 5 lines. The genotype ✕ environment interaction variance components were, on the whole, of much less importance than the genotypic components in this small sample of environments.