Genetic Dissection of Grain Zinc and Iron Concentration, Protein Content, Test Weight and Thousand Kernel Weight in Wheat (Triticum Aestivum L.) through Genome Wide Association Study

Malnutrition due to micronutrients and protein deficiency is recognized among the major global health issues. Genetic biofortification of wheat varieties is both cost-effective and sustainable strategy to contain global micronutrient and protein malnutrition. Genomic regions governing grain zinc concentration (GZnC), grain iron concentration (GFeC), grain protein content (GPC), test weight (TW), and thousand kernel weight (TKW) were investigated in a set of 183 diverse bread wheat genotypes through genome wide association study (GWAS). The RIL population was genotyped using Breeders' 35K Axiom Array and phenotyped in three environments during 2019-2020. A total of 55 marker-trait associations (MTAs) were identified, of which four significant MTAs for GFeC on chromosome 2B, 3A, 3B, 6A and two for GZnC on chromosomes 1A and 7B. Further, a stable SNP was detected for TKW and also identified pleiotropic regions controlling GPC and TKW. In silico analysis revealed a few important putative candidate genes viz., F-box-like domain superfamily, Zinc finger CCCH-type proteins, Serine-threonine/tyrosine-protein kinase, Histone deacetylase domain superfamily and SANT/Myb domain superfamily proteins, etc. The identified novel MTAs will be validated to estimate their effects on different genetic backgrounds for subsequent use in marker-assisted selection (MAS).

Environmental Variability of Thousand Kernel Weight in Maize Hybrids of Different Maturity Groups

Thousand kernel weight (TKW) is an important yield component trait affected by the environmental conditions. This study’s objectives were to determine an environmental variability for the TKW in 32 maize hybrids, sorted in four FAO maturity groups (FAO300, 400, 500 and 600), and to compare 12 environments in Croatia (six locations in two years) according to the joint linear regression and stability analyses across the maturity groups. In general, the effects of the environment, genotype, and their interaction (GEI) were significant. A three-factor ANOVA revealed the greatest and highly significant year effect, while the location effect was non-significant across all four FAO groups. A stability analysis did not detect any preferences with regard to the locations and trends across the FAO groups. It indicates that all locations in the Pannonian region included in this study were suitable for an evaluation of the TKW in maize genotypes belonging to all maturity groups. The TKW seems to be an appropriate yield-component trait for maize breeding due to a high heritability and linear GEI nature.

Effects of nitrogen topdressing and paclobutrazol at different stages on spike differentiation and yield of winter wheat

Background Optimal nitrogen (N) application and plant growth regulators can improve wheat productivity. This can help to improve yield level and ensure food security with limited resources in the Huang-Huai-Hai Plain of China (HPC). Methods A 2-year field experiment was conducted using a randomized block design with four treatments (TS-N topdressing at pseudostem erection stage ; TPS-N topdressing combined with paclobutrazol application at pseudostem erection stage; TJ-N topdressing at jointing stage; TPJ-N topdressing at combined with paclobutrazol application at jointing stage) in 2011–2013. Results The grain number per ear, thousand kernel weight and yield for the TJ and TPJ treatments were higher than those of the TS and TPS treatments. Grain number per ear, yield, and thousands kernel weigh for the TPJ treatment were significantly higher than for the TS and TPS in 2011–2012 (9.82% and 7.27%, 10.23% and 8.99%, 6.12% and 5.58%) and in 2012–2013 (10.21% and 11.55%, 8.00% and 6.58%, 0.00 and 0.00), respectively. Thousands kernel weight under TJ were significantly higher than those under TS and TPS by 13.21% and 14.03%, respectively in 2012–2013. The floret number, significantly correlated with cytokinin content, was also significantly increased under TJ and TPJ at connectivum differentiation stage. For TPJ treatment, the floret number was significantly higher than for the TS, TPS, and TJ by 19.92%, 10.21%, 6.10% in 2011–2012; it was higher than for the TS and TPS by 28.06% and 29.61% in 2012–2013, respectively. The relative expression level of cytokinin oxidase/dehydrogenase gene (TaCKX2.2) was improved during flowering, when cytokinin content was at high level and was also inhibited by paclobutrazol with different degrees. Conclusions Therefore, nitrogen topdressing at jointing stage had increased grain number per ear, thousand kernel weight, and grain yield of wheat. Paclobutrazol could delay spike differentiation and promote cytokinin accumulation that induced expression of TaCKX2.2, maintaining hormonal balance and affecting wheat spike morphogenesis.

The quality of spring wheat and barley grain under the influence of protective-stimulating preparations in the conditions of the forest-steppe zone of the Trans-Urals

The purpose of the research is to study the effect of the fungicide Lamador and the humic preparation Rostok on the quality of spring wheat and spring barley in the conditions of the northern forest-steppe of the Tyumen region. According to the yield, we found that pre-sowing seeds treatment with Lamador protectant and joint treatment with Rostock contributed to an increase in yield by 0.70 t/ha of spring wheat and 0.15 t/ha of spring barley, in the option with the pre-sowing seeds treatment with Lamador protectant and Rostock preparation by 0.90 t/ha and 0.10 t/ha. The highest yield of spring wheat was noted in the third option – 4.10 t/ha, of spring barley in the second option – 3.52 t/ha. An increase in the thousand kernel weight was noted in the crops under study. The highest thousand kernel weight was observed for spring wheat and spring barley in the third option – 30.2 g and 54.3 g, respectively. The maximum protein content in the spring wheat grain was noted in the third option –13.3%, which is higher than the control option by 1.3%, for spring barley we also noted protein increase by 0.4-0.5%. Thus, the experimental application of the fungicide Lamador together with the preparation Rostok for wheat seeds treatment demonstrated a positive effect of the protectants on plants in the agro-climatic conditions of the forest-steppe zone of the Tyumen region and contributed to an increase in crop yield by 28% for spring wheat and 4% for spring barley, which proved the need for their use in the plant protection system, to increase the productivity and quality of the grain obtained.

Study on the Differences in the Responses of Different Winter Wheat Cultivars to Dry Hot Wind

Dry hot wind is one of the main prevailing agro-meteorological disasters during the grain filling stage of winter wheat in Northern China. In this study, three major winter wheat cultivars, including Henong 6119 (HN6119), Gaoyou 5218 (GY5218), and Jimai 325 (JM325) in Hebei Province were selected to analyze their responses to dry hot wind. Under the combined conditions of field natural dry hot wind and artificially simulated dry hot wind experiments, we characterized the three cultivars’ physiological parameters as affected on the day with dry hot wind, and on the day before and after hot wind conditions. Comparative analysis of different correlations among the three cultivars’ physiological parameters toward dry hot wind showed that, during field nature dry hot wind conditions, HN6119 showed less water loss of leaves by reducing the stomatal conductance and transpiration rate, while GY5218 and JM325 showed more water loss of leaves by increasing the stomatal conductance and transpiration rate. The net photosynthetic rate, transpiration rate, and stomatal conductance of HN6119 were recovered during the recovery time after dry hot wind conditions, while these parameters of GY5218 and JM325 showed a continuous decreasing trend. During dry hot wind day, HN6119 showed significant positive correlation between physiological parameters, while GY5218 and JM325 showed poor correlation. The stress of severe dry hot wind on thousand kernel weight (TKW) of HN6119, GY5218 and JM325 is 0.01%, 3.51%, 3.57%, respectively. The stress of mild dry hot wind on thousand kernel weight (TKW) of HN6119, GY5218 and JM325 is 0.36%, 8.12%, 8.84%, respectively. In summary, HN6119 showed strong resistance to dry hot wind, followed by GY5218, and JM325; JM325 had the weakest resistance to dry hot wind.

Association between Grain Size, Shape and Thousand Kernel Weight in Pakistani Wheat Landraces

Wheat (Triticum aestivum. L) grain size is considered to be one of the main criteria of yield constituents by wheat breeders. In order to detect phenotypic diversity and relationship between thousand kernel weight, a collection of 204 landraces from different parts of Pakistan was planted across two years (2012-2014). High throughput method based on seed imaging was used to measure the kernel size and shape. The correlation analysis revealed significant positive correlation between thousand kernel weight (TKW) with perimeter of vertical (PV), thickness (T), area of vertical (AV), area of horizontal (AH), perimeter of horizontal (PH), width (W) and Length (L). Bioplot showed that accessions with high seed shape parameters have higher TKW. By taking TKW as a dependent variable multiple regression analysis was performed. Regression summary indicated that 31% of the variations in TKW are explained by the independent variables. It was shown that grain thickness, length and width are most important for predicting TKW. Based on image analysis this study provides useful information about the relationship between TKW, kernel size and shape in Pakistani wheat landraces that may help to improve grain weight in a breeding program.

Genome wide identification of QTL associated with yield and yield components in two popular wheat cultivars TAM 111 and TAM 112

Two drought-tolerant wheat cultivars, ‘TAM 111’ and ‘TAM 112’, have been widely grown in the Southern Great Plains of the U.S. and used as parents in many wheat breeding programs worldwide. This study aimed to reveal genetic control of yield and yield components in the two cultivars under both dryland and irrigated conditions. A mapping population containing 124 F5:7 recombinant inbred lines (RILs) was developed from the cross of TAM 112/TAM 111. A set of 5,948 SNPs from the wheat 90K iSelect array and double digest restriction-site associated DNA sequencing was used to construct high-density genetic maps. Data for yield and yield components were obtained from 11 environments. QTL analyses were performed based on 11 individual environments, across all environments, within and across mega-environments. Thirty-six unique consistent QTL regions were distributed on 13 chromosomes including 1A, 1B, 1D, 2A, 2D, 3D, 4B, 4D, 6A, 6B, 6D, 7B, and 7D. Ten unique QTL with pleiotropic effects were identified on four chromosomes and eight were in common with the consistent QTL. These QTL increased dry biomass grain yield by 16.3 g m-2, plot yield by 28.1 g m-2, kernels spike-1 by 0.7, spikes m-2 by 14.8, thousand kernel weight by 0.9 g with favorable alleles from either parent. TAM 112 alleles mainly increased spikes m-2 and thousand kernel weight while TMA 111 alleles increased kernels spike-1, harvest index and grain yield. The saturated genetic map and markers linked to significant QTL from this study will be very useful in developing high throughput genotyping markers for tracking the desirable haplotypes of these important yield-related traits in popular parental cultivars.

Allelic diversity study of functional genes in East Africa bread wheat highlights opportunities for genetic improvement

Wheat (Triticum aestivum L.) is a major staple crop in East Africa (EA) providing 9% and 10% of daily calories and protein intake, respectively. However, EA countries depend on import to meet 55% of their domestic wheat supplies due to increasing demands and low domestic yields. To determine the beneficial gene pool currently exploited for wheat improvement in EA, we examined the allelic diversity of 39 genes of breeding importance in a collection of 239 wheat cultivars and breeding lines from Kenya and Ethiopia using KASP markers. The assayed genes have been shown to control variations in plant height, thousand kernel weight (TKW), grain protein content, pre-harvest sprouting (PHS), disease resistance, and flowering time. We observed the beneficial alleles of some major genes including Gpc-B1, Yr5, Yr15, Sr26, and Fhb1 to be missing or present at low frequencies in this population. Furthermore, we validated the effects of the major Rht-1 alleles and TaCKX-D1 in controlling variation in plant height and thousand kernel weight, respectively, under EA conditions. Our results uncover hitherto unexploited allelic diversity that can be used to improve the genetic potential of EA wheat germplasm. This will inform strategies to rapidly mobilize these beneficial alleles for wheat improvement in EA.