Phenotypic variability of bread wheat genotypes for nitrogen harvest index

Nitrogen harvest index (grain nitrogen content over total nitrogen content ratio) is a measure of the efficiency of nitrogen translocation from the vegetative portions of the plant to the grain. It can be recommended as a selection criterion for nitrogen use efficiency improvement. The aim of this study was to investigate nitrogen harvest index in twelve bread wheat genotypes at three nitrogen levels and to classify genotypes according to their phenotypic similarity for the examined trait. The results of factorial ANOVA showed that nitrogen harvest index was influenced mostly by the year ? genotype interaction, year of investigation and genotype; and to the lowest extent by the applied nitrogen rate. Increasing nitrogen doses did not lead to the increased nitrogen harvest index. The calculated nitrogen harvest index values were the highest for wheat growing season 2004/05, and the smallest for the season 2006/07. The highest nitrogen harvest indices were calculated for cultivars Pobeda at the N0 rate and Zlatka at the N100 rate (0.93), and the lowest for cultivar Tamaro at the N0 rate (0.63). Analyzing the constructed dendogram, cultivars Pobeda and Renan at all three levels of nitrogen supply can be singled out as the genotypes with the highest, and cultivar Tamaro as the variety with the lowest harvest index value. The results of this study may be used in developing new high-yielding bread wheat cultivars with improved nitrogen use efficiency. Growing such cultivars would provide the savings in mineral fertilizers and minimize their possible harmful effect on environment.

AMMI analysis of nitrogen harvest index in bread wheat

Nitrogen harvest index - NHI is a measure of efficiency of nitrogen translocation from vegetative organs to grain. The goal of this paper is to investigate variability and stability of nitrogen harvest index of twelve bread wheat genotypes, on three nitrogen levels. ANOVA showed that nitrogen harvest index was mostly under influence of the year x genotype interaction, year of investigation and genotype, and in the smallest amount of the nitrogen rate. Increasing doses of nitrogen did not lead to increased nitrogen harvest index. AMMI analysis showed that most genotypes differed in both the main effect and in GxE interaction. The highest stability i.e. the smallest interaction effect, was found in varieties Axis, Ilona, Sonata and Renan on N0 rate, and in varieties Malyska, Petrana, Axis and Evropa 90 on N100 rate. Cultivar Pobeda with the high average values for nitrogen harvest index, also had small interaction effect, i.e. it proved to be a stable variety.

NITROGEN AND PHOSPHORUS UPTAKE, TRANSLOCATION, AND UTILIZATION EFFICIENCY OF WHEAT IN RELATION TO ENVIRONMENT AND CULTIVAR YIELD AND PROTEIN LEVELS

A field study was carried out in four environments to determine the effects of available water and cultivar on N and P uptake, translocation, and utilization efficiency of wheat (Triticum spp.) cultivars with varying grain yield potential and protein concentration. Two common wheat (T. aestivum L.) cultivars, Neepawa and HY320, and two durum (T. turgidum L. var. durum) cultivars, DT367 and Wakooma, were studied. HY320 and DT367 had higher grain yield potentials and lower protein concentrations than Neepawa and Wakooma. Total plant N and P uptake was proportional to available water, and was strongly associated with dry matter accumulation. From 67 to 102% of plant N and 64–100% of P present at harvest had been accumulated by anthesis. Postanthesis uptake of N and P was greater under moist than under dry environments. There were few cultivar differences in uptake of N or P, and any differences observed were related to variations in plant dry matter. Nitrogen harvest index ranged from 71 to 85% and P harvest index ranged from 81 to 93%. Both indices responded to environment in the same way as grain harvest index; there were no cultivar differences for either N or P harvest index. From 59 to 79% of N and 75 to 87% of P present in vegetative tissues at anthesis was translocated to the grain; translocation did not vary among cultivars. The efficiency of utilization of N and P in production of harvest biomass and grain was directly proportional to water availability and was greater in the high yield cultivars HY320 and DT367 than in Neepawa and Wakooma. There was no evidence that selection for N uptake, translocation, or utilization efficiency would be useful in wheat breeding.Key words: Triticum aestivum L., T. turgidum L. var. durum, nitrogen harvest index, phosphorus harvest index

Inheritance of grain protein concentration, grain yield, and related traits in spring wheat (Triticum aestivum L.)

The inheritance of grain protein concentration (GPC), grain protein yield (GPY), total nitrogen at maturity (TNM), nitrogen harvest index (NHI), grain yield (GY), total dry matter (TDM), and harvest index (HI) were studied in two spring wheat crosses, 'HY521/UM684' and 'HY521/Sinton' in 1985 at Winnipeg and Portage la Prairie, Manitoba. Analysis of variance of parental performance by location indicated that the parents differed significantly for all traits measured and that genotype by location interactions accounted for less than 8% of the observed variation. Generation means analyses indicated that all traits were primarily under genetic control in both crosses with additive gene action being significant for all traits studied. Dominance gene action was detected for all traits but the degree and direction was both trait and genotype specific. Additive × additive epistasis was significant for GPY, TNM, GY, and TDM, but again, was genotype specific. Variance analyses indicated a large genetic component of the variation relative to the environmental component for all traits studied. F2 broad sense heritabilities were moderately high for GPC (0.57–0.76), GPY (0.57–0.76), TNM (0.56–0.73), NHI (0.39–0.59), GY (0.51–0.70), TDM (0.65–0.79) and HI (0.50–0.67). Narrow sense heritabilities were moderately high for GPC (0.50–0.75) and HI (0.49–0.58) but were somewhat lower for GPY (0.26–0.48), TNM (0.27–0.38), NHI (0.24–0.38), GY (0.27–0.39) and TDM (0.32–0.65). Implications of the results of this study on breeding for simultaneous improvement in GPC and GY are discussed.Key words: bread wheat, heritability, grain protein yield, total nitrogen at maturity, nitrogen harvest index, total dry matter, harvest index, breeding strategies.