Mode of inheritance of low-N tolerance adaptive traits in wheat (Triticum aestivum L.) under contrasting nitrogen environments

Abstract

Because of essential economic and ecological concerns, there is increased interest worldwide in developing wheat cultivars that are more efficient in utilizing nitrogen (N) and better suited to N limitations. The objective of the present investigation was to get information on the type of gene action controlling the inheritance of wheat low-N tolerance traits in order to start a breeding program for improving such traits. Six parents of contrasting low-N tolerance were crossed in a diallel fashion. Evaluation of 6 parents, 15 F 1 crosses and 15 F 2 crosses was done using a randomized complete block design with three replications under two levels of soil N, i.e. low-N (0 kg N/ha) and high-N (180 kg N/ha).The magnitude of dominance variance in F 2 's for all studied traits was much greater than that of additive variance under both high N and low N, suggesting that selection should be postponed to later segregating generations in order to eliminate masking effects of dominance variance and take advantage of the additive variance for the improvement of nitrogen use efficiency and grain yield traits. Narrow-sense heritability (h 2 n ) in F 2 's was generally of higher magnitude under low-N than high-N, suggesting that it is better to practice selection for studied nitrogen efficiency and grain yield traits under low-N conditions to obtain higher values of selection gain.Additional keywords: gene action; NUE; NUPE; non-additive; heritability; selection gain Abbreviations used: 100-GW (100-grain weight); BYPP (biological yield/plant); GCA (general combining ability); GPS (grains/ spike); GYPP (grain yield/plant); HI (harvest index); HN (high nitrogen); LN (low nitrogen); NUE (nitrogen use efficiency); NUPE (nitrogen uptake efficiency); NUTE (nitrogen utilization efficiency); SCA (specific combining ability); SPP (spikes/plant) Authors' contributions: Conceived and designed the experiments, and supervised the work: AMMA, RS and MMA. Performed the experiments: ZER. Analyzed the data: AMMA and ZER. Contributed reagents/materials/analysis tools: MMA, AMMA, RS and ZER. Managed the literature searches: AMMA and RS. Wrote the paper: AMMA. All authors read and approved the final manuscript.Supplementary material (Tables S1, S2,

Genetic Diversity Based on Morphological Traits of 19 Maize Genotypes Using Principal Component Analysis and GT Biplot

“…On the contrary, results of the GT biplot in the present study indicated that short ASI was the most reliable secondary trait for improving grain yield under stressed and non-stressed conditions. These results are in agreement with those reported by earlier investigators [45,[55][56][57][58][59][60][61]. These results corroborated the findings of Aci et al [44], who reported that maize landraces characterized by short ASI were the most productive.…”

Secondary Traits for Maize (Zea mays L.) Tolerance to Drought Combined with Reduced N Fertilization Rate

“…Similar to these results, some researchers found a decrease in heritability under stressed environments [22,[30][31][32]64] This is similar to what happened in the present study for 5 out of 12 studied traits, namely DTS, PH, KPR, 100-KW and GYPP, and to some extent under WW-MN environment for 4 traits, namely DTA, EH, EPP and KPP. Others reported that genetic variance and consequently heritability was increased in stressful environments [5,9,10,23,34]. This is similar to that happened in the present study for 3 out of 12 traits, namely ASI, RPE and CCI.…”

“…Moreover, analysis of variance of the RCBD indicated the significance of differences among studied genotypes for all such traits under each of the six environments. Such genotypic differences in studied traits under all studied stressed and non-stressed environments were also recorded by previous investigators in maize [5,6,10,[44][45][46][47].…”

“…The low estimates of heritability of some traits under some environments indicate that environmental variance and/or genetic × environment variance had great effect on the performance of these traits. Low heritability estimates for these traits, could also be attributed to the small magnitude of genotypic variance relative to that of the phenotypic variance as suggested by [4,5,47,63]. It is also obvious from these results that h 2 b estimates were generally the highest under full irrigation as compared to those under drought stress for 20 out of 21 studied traits, but under medium N for five traits, low-N for seven traits and under water stress only for one trait (CCI).…”

“…This expose maize plants to drought and/or low-N stresses. Exposing maize plants to such stresses results in a huge reduction in grain yields [2][3][4][5][6] for drought and [7][8][9][10] for low-N. This necessitates that maize breeders should pay great attention to develop drought-tolerant and low-N tolerant maize cultivars that could give high grain yield under such stressed conditions.…”