Physiological characteristics of recent Canada Western Red Spring wheat cultivars: Components of grain nitrogen yield

Abstract

Genetic yield gains have been difficult to achieve within the Canada Western Red Spring (CWRS) wheat (Triticum aestivum L.) class, partially because of the requirement for high protein concentration. A previous study indicated that four newer, high-yield CWRS cultivars (registered 1994–1997) also had higher protein yields. The objective of the present study was to determine if the increase in grain nitrogen (protein) yield of the four newer wheat cultivars, relative to two older cultivars, Neepawa (registered in 1969) and Marquis (introduced in 1909), resulted from increased plant nitrogen uptake, more efficient utilization of nitrogen, or a combination of these factors. The higher nitrogen yields were primarily attributed to more efficient utilization and redistribution of the nitrogen rather than increased uptake of soil nitrogen. The nitrogen harvest index (NHI) of the new cultivars, considered as a group, was higher than the NHI of Neepawa, which in turn was higher than that of the much older cultivar Marquis. The NHI of each of the new cultivars was higher than that of Marquis. The nitrogen concentration in the non-grain tissue at maturity (NGNCM) of the new cultivars, considered as a group, was lower than that of Neepawa, which in turn was lower than the NGNCM of Marquis. At maturity, all five tissues (leaf blade, stem plus sheath, peduncle, glume, and rachis) for the new cultivars and Neepawa had lower nitrogen concentrations than for the corresponding tissues of Marquis. The nitrogen concentration of the peduncle and leaf-blade tissues of the new cultivars, as a group, were also lower at maturity than the corresponding nitrogen concentrations for Neepawa. The results suggest that low non-grain nitrogen concentration at harvest is associated with improved NHI and grain nitrogen yield in CWRS wheat. This information may improve our understanding of the higher protein yields that have been achieved within this class, and assist in the selection of future parents. Key words: Nitrogen harvest index, nitrogen uptake, nitrogen yield, protein, remobilization, Triticum aestivum