Abstract
A set of thirty-six wheat cultivars were grown for two consecutive years under low and high nitrogen conditions. The interactions of cultivars with different environmental factors were shown to be highly significant for most of the studied traits, suggesting the presence of wider genetic variability which may be utilized for the genetic improvement of desired trait(s). Three cultivars, i.e., RAJ 4037, DBW 39 and GW 322, were selected based on three selection indices, i.e., tolerance index (TOL), stress susceptibility index (SSI), and yield stability index (YSI), while two cultivars, HD 2967 and MACS 6478, were selected based on all four selection indices which were common in both of the study years. According to Kendall’s concordance coefficient, the consistency of geometric mean productivity (GMP) was found to be highest (0.778), followed by YSI (0.556), SSI (0.472), and TOL (0.200). Due to the high consistency of GMP followed by YSI and SSI, the three selection indices could be utilized as a selection tool in the identification of high-yielding genotypes under low nitrogen conditions. The GMP and YSI selection indices had a positive and significant correlation with grain yield, whereas TOL and SSI exhibited a significant but negative correlation with grain yield under both high and low nitrogen conditions in both years. The common tolerant genotypes identified through different selection indices could be utilized as potential donors in active breeding programs to incorporate the low nitrogen tolerant genes to develop high-yielding wheat varieties for low nitrogen conditions. The study also helps in understanding the physiological basis of tolerance in high-yielding wheat genotypes under low nitrogen conditions.
Highlights
Wheat is an important cereal crop, accounting for about 20 percent of the calories consumed by the human population across the globe
The genotype effect is significant for all the studied traits, whereas genotype × year effect was significant for all the studied traits except GWPS, CHL, grain yield (GY) under high N and fertile shoots m−1 (FS), GWPS, canopy temperature (CT) under low N conditions
The genotype effect is significant for all the studied traits, whereas genotype × year effect was significant for all the studied traits except GWPS, CHL, and GY under high N (HN) and FS, GWPS, and CT under low N (LN) conditions
Summary
Wheat is an important cereal crop, accounting for about 20 percent of the calories consumed by the human population across the globe. Agronomy 2020, 10, 417 globally, wheat accounts for nearly one-third of crop fertilizer use. The development of wheat genotypes with high nitrogen use-efficiency would be of economic benefit to farmers, and help to reduce environmental pollution associated with the excessive use of nitrogen fertilizers [4,5]. To increase the grain yield of wheat crop, the aboveground biomass should be increased without compromising the harvest index. This implies an additional requirement of nitrogen (N) to support the increased photosynthesis and biomass production [7,8]
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