To determine the effects of different seeding rates and nitrogen fertilizer levels on yield and its components of six bread wheat genotypes, a field experiment was conducted at East Canal and Al Marashda Agricultural Research Stations during the 2018-2019 and 2019-2020 growing seasons. The experiment was laid out in a split-split plot arrangement in a Randomized Complete Block Design with three replications. Seeding rates (60, 80, and 100 kg fad.-1 ) were placed in the main plots, while nitrogen fertilizer levels (75,100 and 125 kg N fad. -1 ) were allotted in the subplots, whereas, the sub-sub plots were allocated to the bread wheat genotypes (Gemmeiza 12, Sids 14, Shandaweel 1, Line 1, Line 2 and Line 3). The number of spikes m -2 , 1000 kernels weight, and grain yield were significantly higher at a seeding rate of 100 kg fad. -1 as compared to other seeding rates. Nitrogen fertilizer levels affected significantly yield and its components. Grain yield and its components increased with each increment in nitrogen fertilizer level from 75 to 100 and up to 125 kg N fad -1 . Wheat is sown at a seeding rate of 100 kg fad. -1 with 125 kg N fad. -1 gave the highest number of spikes m -2 and grain yield. The interaction effects of seeding rate by genotypes and nitrogen levels by genotypes reveal the superiority of Sids 14 and Shandaweel 1 wheat cultivars in grain yield when sown at a seeding rate of 100 kg fad. -1 with 125 kg N fad. -1 in both locations.

Salinity stress harms crop yield and productivity worldwide. This study aimed to identify genotypes with higher grain yield and/or salinity tolerance from forty bread wheat genotypes evaluated under seawater diluted at 4.0, 8.0, or 12.0 dS/m or control (0.4 dS/m) in the 2019/20 and 2020/21 seasons. Six elite genotypes, namely 6, 16, 31, 33, 34, and 36, were chosen and tested in a lysimeter under diluted seawater stress in 2020/21. The results showed significant differences (p ≤ 0.01) among the genotypes for the traits grain yield (GY), harvest index (HI), chlorophyll content index (CCI), chlorophyll fluorescence parameter Fv/Fm, and their interaction with salinity treatments. Additionally, significant differences (p ≤ 0.01) were detected among ten genotypes for all agronomic traits along with spectral reflectance indices (SRI), e.g., curvature index (CI), normalized difference vegetation index (NDVI), triangular vegetation index (TVI), modified chlorophyll absorption reflectance index (MCARI), and their interaction with salinity treatments. Genotype by traits (GT) and genotype by yield*trait (GYT) biplots are useful for genotypes screening and selection based on grain yield and other associated traits (agronomic, physiological traits, and spectral reflectance indices combinations) as well as genotypes by stress tolerance indices (GSTI). In conclusion, this study identified that genotypes 6, 16, 31, 33, 34, and 36 in the 2019/20 season and genotypes 2 and 1 performed better than Kharchia 65 and Sakha 8 in the 2020/21 season, which welected as superior genotypes and might be recommended for sowing and/or inclusion in the breeding program in salt-affected soils. It was possible to draw the conclusion that spectral reflectance indices were efficient at identifying genotypic variance.

IntroductionSalinity is the abiotic obstacle that diminishes food production globally. Salinization causes by natural conditions, such as climate change, or human activities, e.g., irrigation and derange misuse. To cope with the salinity problem, improve the crop environment or utilize crop/wheat breeding (by phenotyping), specifically in spread field conditions. For example, about 33 % of the cropping area in Egypt is affected by salinity.MethodsTherefore, this study evaluated forty bread wheat genotypes under contrasting salinity field conditions across seasons 2019/20 and 2020/21 at Sakha research station in the north of Egypt. To identify the tolerance genotypes, performing physiological parameters, e.g., Fv/Fm, CCI, Na+, and K+, spectral reflectance indices (SRIs), such as NDVI, MCARI, and SR, and estimated salinity tolerance indices based on grain yield in non-saline soil and saline soil sites over the tested years. These traits (parameters) and grain yield are simultaneously performed for generating GYT biplots.ResultsThe results presented significant differences (P≤0.01) among the environments, genotypes, and their interaction for grain yield (GY) evaluated in the four environments. And the first season for traits, grain yield (GY), plant height (PH), harvest index (HI), chlorophyll content index (CCI), chlorophyll fluorescence parameter Fv/Fm, normalized difference vegetation index (NDVI) in contrasting salinity environments. Additionally, significant differences were detected among environments, genotypes, and their interaction for grain yield along with spectral reflectance indices (SRIs), e.g., Blue/Green index (BIG2), curvature index (CI), normalized difference vegetation index (NDVI), Modified simple ratio (MSR). Relying on the genotype plus genotype by environment (GGE) approach, genotypes 34 and 1 are the best for salinity sites. Genotypes 1 and 29 are the best from the genotype by stress tolerance indices (GSTI) biplot and genotype 34. Genotype 1 is the best from the genotype by yield*trait (GYT) method with spectral reflectance indices.DiscussionTherefore, we can identify genotype 1 as salinity tolerant based on the results of GSTI and GYT of SRIs and recommend involvement in the salinity breeding program in salt-affected soils. In conclusion, spectral reflectance indices were efficiently identifying genotypic variance.

Considering the rapid climatic changes in the past few years, the effect of high temperature on wheat productivity is global concern. Heat stress is one of the major abiotic stresses reducing wheat production. Heat stress reduces grain weight and number, chlorophyll content and photosynthesis activity. This study was carried out during two successive seasons 2018/2019 and 2019/2020 at Almatana agricultural Research Station, Luxor, Upper Egypt, to investigate the effect of two sowing dates 20 th November (favorable sowing date) and 10 th January (late sowing date, after sugarcane harvest) on yield characters, of twenty bread wheat genotypes. The objective was to understand heat stress effects on grain yield and its components to estimate some selection indices for heat tolerance in wheat. The studied characters were number of spikes/m2, number of kernels/spike, 1000-kernel weight and grain yield (ton/ha). Results indicated that sowing dates and genotypes had significant effects for all studied characters. Delaying sowing date after sugarcane harvest reduced no. of spikes/m 2 , no. of kernels/spike, 1000-kernel weight and grain yield by an average of 31.62, 32.85, 32.76 and 37.74%, respectively, compared to the favorable sowing date. Highest grain yield (8.81) t/ha under favorable sowing date was for gemmeiza11, while shandaweel1 gave (5.92) t/ha the highest grain yield under late sowing date. Heat susceptibility index (HSI) over all two seasons ranged from 0.78 for Shandaweel1, to 1.23 for genotype Line8.