Days To Heading Research Articles

Evaluation of Bread Wheat (Triticum aestivum L.) Germplasm for Wheat Rust Diseases Resistance and Yield Performance

The most important biotic constraints for wheat production in Ethiopia are Wheat rust diseases, insects, and weeds. Among wheat rust diseases, stem rust and yellow rust are the more limiting factors for yield. A study was undertaken at Kulumsa and Melkasa in alpha lattice design with two replications from July to December 2023 to evaluate the performance of introduced bread wheat materials from CIMMYT for wheat rust diseases and yield. Data were collected for stem rust, yellow rust, and agronomic traits, including grain yield. The ANOVA showed high and significant genotypic variation (p<0.05) on Days to heading (DTH), Hectoliter weight (HLW), Thousand kernels weight (TKW), and Yield (YLD). Then, the result from LSD mean comparision revealed genotypes: EBW222102 YLD=7.7 t ha-1, EBW222106 YLD= 7.61 t ha-1, EBW222108 YLD=7.66 tha-1, EBW222136 YLD= 7.76 t ha-1 to be significantly higher than the check variety Daka YLD= 6.22 t ha-1 (p<0.05) at Kulumsa. Genotypes: EBW222108, EBW222109, EBW222111, EBW222112, EBW222114, EBW222125, EBW222142, and EBW222143 showed resistance to moderate resistance for yellow rust and stem rust across both locations. About eighteen genotypes were susceptible to stem rust diseases with the coefficient of infection YRCI≥30 at Melkasa. Genotypes EBW222111, EBW222126, EBW222129, EBW222134, and EBW222142 delivered high yield, greater than or equal to 2 t ha-1 at Melkasa. Generally, selection for disease resistance and high-yielding genotypes enable the development and release of noble varieties for wheat-producing farmers.

Genome-wide association analysis revealed genetic markers linked to grain yield and yield related traits in finger millet grown in acidic soils

Abstract Aim Soil acidity has a major impact on the finger millet yield and productivity as tolerant cultivars that perform well in acidic soils are limited. This study aimed at evaluating major finger millet phenotypic traits under acidic soils followed by identifying associated markers. Method A total of 288 finger millet genotypes were field evaluated for 8 major phenotypic traits including grain yield under acid soil conditions at two independent locations (Bako and Gute) in Ethiopia. In parallel, the same genotypes were subjected to genotyping-by-sequencing to generate single nucleotide polymorphism markers to be used in the association panel. Results Phenotypic data analysis revealed significant phenotypic variation in all the targeted traits among the studied genotypes. Genotypes Ec-100093, Ec-215803, and Ec-203322 were relatively high-yielding, whereas genotypes Ec-229721 and Ec-242110 had the lowest grain yield across the two locations. The broad-sense heritability of the traits ranged from 0.04 for the number of effective tillers (NET) to 0.78 for days to emergence (DE). The marker-trait association analysis revealed 23 SNP markers significantly associated with one or more traits. Among the 23 significant markers, one marker associated with DE, seven with days to heading (DH), four with days to maturity (DM), one with plant height (PH), two with number of fingers, two with ear length (EL), three with the number of effective tillers (NET) and three with grain yield (GY). Conclusions The identified novel markers associated with the targeted traits will potentially be useful for genomics-driven finger millet improvement in acidic soils.

Phenotypic Selection of Bread Wheat (Triticum aestivum L.) Elite Lines for Diseases Resistance and Yield Potential

Wheat diseases and pests globally threaten wheat production. Wheat rust diseases are the most distractive biotic constraint of wheat in Ethiopia. Therefore, this experiment aimed to select and develop wheat rust resistance bread wheat varieties for the farmers. The result of the study revealed highly significant variation existed among tested genotypes for Plant Height (PHT), Days to Heading (DTH), Days to Maturity (DTM), Thousand Kernel Weight (TKW), Hectoliter Weight (HLW), and Yield (YLD) at (P< 0.001). Out the forty-nine introduced genotypes, five genotypes: EBW222153, EBW222159, EBW222160, EBW222162, and EBW222164, showed resistance to moderately resistance for both yellow rust and stem rust diseases across the two test locations. Also, they delivered high average yield: 5.9 tha-1, 4.46 tha-1, 5.17tha-1,4.15 tha-1, and 4.79tha-1 respectively. Furthermore, all the above-mentioned genotypes, except EBW222162, showed significantly higher yield at (P<0.05) than the check variety, Shaki. Furthermore, EBW222153, EBW222159, EBW222160, EBW222162, EBW222164, and EBW222178 would resistance to moderately resistance for stem rust at Melkasa. Thus, the selection of these genotypes and advancing to the next stage of breeding pipelines enables to release noble bread wheat varieties for the farmers.

Genome‐Wide Association Studies Predicted Drought Stress Occuring at Anthesis and Post‐Anthesis Stages in Novel Diverse Germplasm of Bread Wheat (Triticum aestivum)

ABSTRACTThis study employed genome‐wide association studies (GWAS) to identify the crucial marker–trait associations (MTAs) for agronomic and physiological traits in bread wheat grown under full irrigation and 40% reduced irrigation. One hundred twenty‐four genotypes derived from three‐way crosses of landraces and synthetic bread wheat were evaluated for 2 years in the field conditions of CIMMYT Obregon, Mexico. Irrigation was not provided at anthesis and post‐anthesis stage for the drought treatment, and data of 12 traits were recorded. Most of the traits were reduced significantly under drought conditions except for vigour, wax and spike length (SL); genotypes were significantly different for the eight traits except for days to heading (DTH), number of grains spike−1 (NGS), normalized difference in vegetation index (NDVI) and canopy temperature depression (CTD); and differences were also significant for five traits between the years. Moreover, GY was significantly and negatively correlated with wax and CTD. Our GWAS results indicated 117 significant (p ≤ 0.001) MTAs distributed on all the wheat chromosomes except chromosomes 4B and 4D explaining 10%–21.5% of the phenotypic variation of the corresponding traits. Moreover, 22 MTAs were recorded for grain yield and explaining the phenotypic variations up to 14.7% with one common association under both irrigated and drought conditions. Additionally, we also identified the associations for NDVI, CTD and SL at chromosome 1B, suggesting that genotypes are sustaining superior grain yield through better values of traits like NDVI, CTD, and SL under the challenging conditions of anthesis and post‐anthesis drought stress.

Genome-wide association and genomic prediction study of elite spring bread wheat (Triticum aestivum L.) genotypes under drought conditions across different locations

Abiotic stress, notably drought, impacts wheat production globally, but more so in central and South Asia, North Africa (CWANA), and sub-Saharan Africa (SSA). The current study attempts to identify significant markers linked to drought and heat tolerance and assess genomic prediction. A genome-wide association study was conducted using the 10 K wheat SNP markers for grain yield and related traits of 246 spring bread wheat genotypes from ICARDA. Traits including grain yield (GY), days to heading (DHE), days to maturity (DMA), plant height (PLH), and thousand kernel weight (TKW), were evaluated across six different locations, spanning two years 2015–2016 and 2016–2017, as per variance analysis. Grain yield and related-traits showed a considerable variation among genotypes. Moreover, GWAS using a mixed linear model (MLM), revealed 65 marker-trait associations (MTAs) across the six environments on 16 chromosomes. With an average r2 value of 0.26, Genome D has the highest linkage, followed by Genomes B and A with r2 values of 0.22 and 0.21, respectively. GY had the highest MTA rating (35), followed by TKW (9) and 3 for each of the other agronomic traits (DHE, DMA, PLH) at Merchouch station. The marker “CAP8_c1393_327” was the most significant associated marker correlated with grain yield located on chromosome 3 A across Sid El Aidi station. Additionally, the SNP markers “wsnp_Ra_c26091_35652620” displayed extremely significant and stable MTA for TKW on chromosome 5B at Merchouch station. The markers and candidate genes reported throughout this study have the potential to be used in marker-assisted selection to enhance wheat genotypes in terms of yield and resistance to drought limitations.

Enhanced radiation use efficiency and grain filling rate as the main drivers of grain yield genetic gains in the CIMMYT elite spring wheat yield trial

Common wheat (Triticum aestivum L.) is a major staple food crop, providing a fifth of food calories and proteins to the world’s human population. Despite the impressive growth in global wheat production in recent decades, further increases in grain yield are required to meet future demands. Here we estimated genetic gain and genotype stability for grain yield (GY) and determined the trait associations that contributed uniquely or in combination to increased GY, through a retrospective analysis of top-performing genotypes selected from the elite spring wheat yield trial (ESWYT) evaluated internationally during a 14-year period (2003 to 2016). Fifty-six ESWYT genotypes and four checks were sown under optimally irrigated conditions in three phenotyping trials during three consecutive growing seasons (2018–2019 to 2020–2021) at Norman E. Borlaug Research Station, Ciudad Obregon, Mexico. The mean GY rose from 6.75 (24th ESWYT) to 7.87 t ha−1 (37th ESWYT), representing a cumulative increase of 1.12 t ha−1. The annual genetic gain for GY was estimated at 0.96% (65 kg ha−1 year−1) accompanied by a positive trend in genotype stability over time. The GY progress was mainly associated with increases in biomass (BM), grain filling rate (GFR), total radiation use efficiency (RUE_total), grain weight per spike (GWS), and reduction in days to heading (DTH), which together explained 95.5% of the GY variation. Regression lines over the years showed significant increases of 0.015 kg m−2 year−1 (p < 0.01), 0.074 g m−2 year−1 (p < 0.05), and 0.017 g MJ−1 year−1 (p < 0.001) for BM, GFR, and RUE_total, respectively. Grain weight per spike exhibited a positive but no significant trend (0.014 g year−1, p = 0.07), whereas a negative tendency for DTH was observed (− 0.43 days year−1, p < 0.001). Analysis of the top ten highest-yielding genotypes revealed differential GY-associated trait contributions, demonstrating that improved GY can be attained through different mechanisms and indicating that no single trait criterion is adopted by CIMMYT breeders for developing new superior lines. We conclude that CIMMYT’s Bread Wheat Breeding Program has continued to deliver adapted and more productive wheat genotypes to National partners worldwide, mainly driven by enhancing RUE_total and GFR and that future yield increases could be achieved by intercrossing genetically diverse top performer genotypes.

Effects of post-flowering drought and supplemental irrigation on grain yield and agro-phenological traits in durum wheat

Water deficit and unbalanced distribution rainfall in the Mediterranean rainfed regions are major problems threatening agricultural sustainability, especially durum wheat (Triticum turgidum L. var. durum) production. This study aimed to investigate the effects of drought and supplemental irrigation in post-flowering stage on traits performance of durum wheat trials and to identify traits that significantly contribute to increase the grain yield of durum wheat under different water regimes and recommend new genotypes adapted to climate change. An eight-year field study was conducted from 2014 to 2022, consisting of 36 field experiments, 18 under rainfed and 18 under supplemental irrigation (two times irrigation in flowering and grain-filling stages) conditions through six experimental series of elite durum wheat yield trials each with same genotypes. In each experiment, grain yield, 1000-kernel weight (TKW), plant height (PLH), days to heading (DHE) and maturity (DMA) were recorded. Drought stress tolerance index (STI) and mean productivity (MP) were applied to differentiate high-performing and drought tolerant durum wheat genotypes in each experimental series. The combined analysis of variance for traits studied of each experimental series indicated that the year, water stress treatment, genotype and their interaction effects were significant. For grain yield, year was the main source of variation and had the highest impact on genotypes performance. The results indicated that the supplemental irrigation, depending on genetic materials, significantly increased grain yield (18.7%-45.8%), TKW (8.2%-12.9%), and PLH (1.1%-8.2%) compared with the rainfed condition across years. Supplemental irrigation exhibited for no significant effect on the increase of the maturity time (0.2%-2.2%) of genotypes tested compared with the rainfed condition. The results confirmed the systematic effects of post-flowering drought on yield, grain weight and plant stature of durum wheat. A positive and significant trend (R2=0.62; P<0.01) was observed between yield production in rainfed condition and cumulative rainfall, showing that in 62% of the cases higher rainfall resulted in higher performance. TKW and PLH significantly and positively correlated with mean yield in the both rainfed and irrigated conditions, suggesting the importance of these two traits in breeding programs to assist in developing high yielding genotypes under different water regime conditions. Evaluation of genotypes in terms of mean yield and stability performance using GGE biplot, resulted in identification of superior lines that outperformed the check cultivars. The STI and MP were desirable selection criteria for high yielding and drought tolerant genotypes, thus high yielding genotypes that are tolerant to drought would be expected to have good yield stability in stressful environments. The results highlight the significant effects of drought stress after flowering upon grain yield, and the significant contribution of 1000-kernel weight and plant height to increase grain yield under different water regimes, that could be utilized to aid breeding of high-performing and drought tolerant durum wheat genotypes under the future climate conditions.

QTL-seq analysis identified the genomic regions of plant height and days to heading in high-latitude rice.

Introduction: Rice (Oryza sativa L.) is one of the most extensive crops in the world. China's Heilongjiang Province is the northernmost rice-growing region in the world. However, rice cultivars suitable for growth in low-latitude regions may not mature normally due to their distinct climate and short frost-free period. It is necessary to precisely determine the frost-free period for each region to make the best use of the rice growth stage so as to ensure the maturity and yield of different rice cultivars in Heilongjiang Province. The time span of the heading stage is a key parameter for evaluating the adaptability of a rice cultivar to a specific rice-growing region. Given the above facts, it is of high importance to study the associated genes and sites controlling days to heading (DH) and plant height (PH) of rice in Heilongjiang Province. Bulked segregant analysis (BSA) combined with high-throughput sequencing can effectively exclude interferences from background genomic differences, making it suitable for analyzing the associated sites of complex agronomic traits in early generations. Methods: In this study, an F3 segregating population was obtained by crossing two main cultivars that are grown under different temperatures and day-light conditions in Heilongjiang. Two pools of extreme phenotypes were built for the DH and PH of the population. For SNP and InDel variants obtained from whole-genome resequencing in the pools, an association analysis was performed using the Euclidean distance (ED) algorithm and the SNP/InDel index algorithm. Results: The intersection of SNP and InDel regions associated with the phenotypes was considered to obtain the final associated sites. After excluding interferences from the cloned genes on chromosomes 2 and 7, a total length of 6.34Mb on chromosomes 1, 3, and 10 and 3.16Mb on chromosomes 1 and 10 were left associated with PH and DH, respectively. Then, we performed a gene annotation analysis for candidate genes in the remaining regions using multiple genome annotation databases. Our research provides basic data for subsequent gene mapping and cloning. Discussion: By mining more genetic loci associated with the days to heading and plant height of rice, we may provide abundant genetic resources for refined molecular breeding in Heilongjiang Province.

Trait Based Selection of Elite Wheat Genotypes under Irrigated, Heat Stress, and Heat Drought Conditions

Environmental factors affects yield and yield-attributing parameters of wheat. To explore direct and indirect association and to identify the most appropriate trait for trait based selection of elite wheat genotypes under irrigated, heat stress and heat drought conditions, correlation, path and principal component analysis were performed. The field experiment was conducted using serpentine alpha lattice design at the agronomy farm of the Institute of Agriculture and Animal Science (IAAS), Paklihawa campus, Nepal that comprised of twenty elite wheat genotypes. The grain yield of wheat was found to have significant negative association with days to heading (DTH) and days to booting (DTB) under all tested conditions. Plant height (Ph) was found to have a significant negative association with grain yield of wheat under irrigated conditions while significant positive association was observed across heat stress and heat drought conditions (p≤0.05). DTB, DTH, and Ph had a direct influence on the yield across all tested conditions. For the breeding program, dwarf genotypes that are earlier in booting and heading should be promoted under irrigated conditions whereas the taller genotypes that are earlier in booting and heading should be promoted under heat stress and heat drought conditions. Based on selected traits, BL 4919 and NL 1350 were selected as high yielding genotypes under irrigated condition, NL 1369 and NL 1417 under heat stress condition and NL 1350 and Bhrikuti under the heat drought condition. These genotypes should be promoted in the varietal improvement program of Nepal to release as a potential climate resilient variety.

Acceleration of wheat breeding: enhancing efficiency and practical application of the speed breeding system

BackgroundCrop breeding should be accelerated to address global warming and climate change. Wheat (Triticum aestivum L.) is a major food crop. Speed breeding (SB) and speed vernalization (SV) techniques for spring and winter wheat have recently been established. However, there are few practical examples of these strategies being used economically and efficiently in breeding programs. We aimed to establish and evaluate the performance of a breeder-friendly and energy-saving generation acceleration system by modifying the SV + SB system.ResultsIn this study, a four-generation advancement system for wheat (regardless of its growth habits) was established and evaluated using an energy-efficient extended photoperiod treatment. A glasshouse with a 22-hour photoperiod that used 10 h of natural sunlight and 12 h of LED lights, and minimized temperature control during the winter season, was successful in accelerating generation. Even with one or two field tests, modified speed breeding (mSB) combined with a speed vernalization system (SV + mSB) reduced breeding time by more than half compared to traditional field-based methods. When compared to the existing SV + SB system, the SV + mSB system reduced energy use by 80% to maintain a 22-hour photoperiod. Significant correlations were found between the SV + mSB and field conditions in the number of days to heading (DTH) and culm length (CL). Genetic resources, recombinant inbred lines, and breeding materials that exhibited shorter DTH and CL values under SV + mSB conditions showed the same pattern in the field.ConclusionsThe results of our SV + mSB model, as well as its practical application in wheat breeding programs, are expected to help breeders worldwide incorporate generation acceleration systems into their conventional breeding programs.

Impact of rising temperatures on historical wheat yield, phenology, and grain size in Catalonia.

Climate change poses significant challenges to agriculture, impacting crop yields and necessitating adaptive strategies in breeding programs. This study investigates the genetic yield progress of wheat varieties in Catalonia, Spain, from 2007 to 2021, and examines the relationship between genetic yield and climate-related factors, such as temperature. Understanding these dynamics is crucial for ensuring the resilience of wheat crops in the face of changing environmental conditions. Genetic yield progress was assessed using a linear regression function, comparing the average yield changes of newly released wheat varieties to benchmark varieties. Additionally, a quadratic function was employed to model genetic yield progress in winter wheat (WW). The study also analyzed correlations between genetic yield (GY) and normalized values of hectoliter weight (HLW) and the number of grains (NG) for both spring wheat (SW) and WW. Weather data were used to confirm climate change impacts on temperature and its effects on wheat growth and development. The study found that genetic yield was stagnant for SW but increased linearly by 1.31% per year for WW. However, the quadratic function indicated a possible plateau in WW genetic yield progress in recent years. Positive correlations were observed between GY and normalized values of HLW and NG for both SW and WW. Climate change was evident in Catalonia, with temperatures increasing at a rate of 0.050 °C per year. This rise in temperature had detrimental effects on days to heading (DH) and HLW, with reductions observed in both SW and WW for each °C increase in annual minimum and average temperature. The findings highlighted the urgent need to address the impact of climate change on wheat cultivation. The stagnation of genetic yield in SW and the potential plateau in WW genetic yield progress call for adaptive measures. Breeding programs should prioritize phenological adjustments, particularly sowing date optimization, to align with the most favorable months of the year. Moreover, efforts should be made to enhance HLW and the number of grains per unit area in new wheat varieties to counteract the negative effects of rising temperatures. This research underscores the importance of ongoing monitoring and adaptation in agricultural practices to ensure yield resilience in the context of a changing climate.

Development of Short Duration, Tolerance to High Temperature and Bipolaris Leaf Blight, and Moderately Susceptible to Blast Disease of Wheat Genotype with Trials in Various Agroecological Zones in Bangladesh

Wheat production in Bangladesh faces to the detrimental effects of biotic and abiotic stresses that have been exacerbated by climate change. The development of short duration, high temperature and disease tolerant wheat variety is the most importance to produce higher yield combating the deleterious effects of the stresses. Some wheat lines (line was expressed by E) were evaluated at the different research stations of Bangladesh Wheat and Maize Research Institute (BWMRI) and farmers’ fields in consecutively three years under irrigated timely sowing (ITS) and irrigated late sowing (ILS) conditions. The days to heading (DH), days to maturity (DM), plant height (PH), spikelet spike-1 (SPS), grain spike-1 (GPS), thousand grain weight (TGW), and grain yield were depicted comparatively higher in ITS and ILS than ITS, but the severity of Bipolaris leaf blight (BpLB) and blast diseases were exhibited lower in BAW 1194 (E9) line than check varieties and other lines same conditions (BAW = Bangladesh Advanced Wheat). Those phenotypic and yield contributing characters, and BpLB and blast diseases were also observed lower in ILS than other genotypes. Further, E9 exhibited the lower percentage of yield loss in the ILS compared to ITS than check and other genotypes indicated its high temperature tolerance. In addition, E9 exhibited relatively higher grain yield than other genotypes in the candidate variety demonstration and multiplication yield trials. Therefore, BAW 1194 line may be released as a short duration, tolerance to high temperature and BpLB, and moderately tolerance to blast disease wheat variety to accelerate wheat production.

Evaluation of Genotypic Variability and Analysis of Yield and Its Components in Irrigated Rice to Stabilize Yields in the Senegal River Valley Affected by Climate Change

Rice is an important cereal crop in many countries, but its production in the Senegal River Valley is hampered by adverse climatic conditions. This study was aimed at evaluating the diversity among genotypes and the association between several phenological and yield attributes of irrigated rice to mitigate the consequences of climate change. During the dry season of 2013–2014, 300 irrigated high yielding oryza sativa indica panel were used in an Alpha-lattice experiment at the Ndiaye research station in Senegal. Results revealed considerable differences between genotypes in yield and yield attributes. Grain yields ranged between 1378 and 9776 kg/ha. There were also substantial differences in the genotypic and phenotypic coefficients of variation, broad-sense heritability, genetic advance, and genetic advance as a percentage of the mean between evaluated traits. Days to heading (DH) had a higher broad-sense heritability (67.31%), indicating that the chances of transferring this trait for selection purposes will be higher, and genotypes may be used to generate early or late flowering lines. Significant positive and negative correlations were found between the studied traits and grain yield. Path analysis indicated that the maximum positive direct impact was observed with the harvest index (0.256), and the maximum negative direct effect was observed with the days to heading (−0.142). Results showed that 56 accessions outperformed the local check Giza 178, whose yield was 8987 kg/ha. Using principal component analysis and a dendrogram, genotypes were classified into four groups. The plant materials had significant variability and may be utilized to develop desired features in rice-breeding programs.

Farklı Çevrelerde Yetiştirilen Bazı Ekmeklik Buğday Çeşitlerinin (Triticum aestivum L.) Bazı Fizyolojik ve Verim Özelliklerinin Değerlendirilmesi

This study aimed to evaluate the performance of some bread wheat varieties in different environments, and to reveal the relationships between some physiological parameters and yield and yield components. Three bread wheat varieties, (Namely, Basribey 95, Alibey, and Kaşifbey 95), were used as plant materials. Field experiments were conducted during the 2009-2010 and 2010-2011 growing seasons in Aydın and Menemen locations. The experimental layout was a RCBD with three replications at each location and year. In the study, canopy temperature depression (CTD), chlorophyll content (CC), stomatal conductance (SC), grain yield (GY), plant height (PH), spike number per square meter (S/m2), thousand kernel weight (TKW), test weight (TW), grain number per spike (G/S), single spike yield (SSY), number of days to heading (DHE), were examined. CTD in ZGS 65 had a decisive role in gaining high grain yield. Also, CC in ZGS 65 and ZGS 71 might be defined as an important physiological traits. On the other hand, the contribution of the SC parameter determined in ZGS 55, ZGS 65 and ZGS 71 to the yield depends on the environment. Those parameters could be selection criteria for high-yield wheat breeding due to positive and significant correlations with grain yield. And also SC and CC parameters might be used in yield estimation on wheat.

Evaluation of Wheat Genotypes under Water Regimes Using Hyperspectral Reflectance and Agro-Physiological Parameters via Genotype by Yield*Trait Approaches in Sakha Station, Delta, Egypt

Drought is an environmental abiotic stress that diminishes wheat production worldwide. In the present study, we evaluated fifty bread wheat genotypes (arranged in alpha lattice design) under two main water regimes, water-deficit (two surface irrigations) and well-watered (four irrigations), at different sites in two consecutive cropping seasons, 2019/20 and 2020/21. To identify the drought-tolerant genotypes, utilized several selection/phenotyping criteria, including agronomic traits, e.g., grain yield (GY) and yield components (SM); physiological parameters such as canopy temperature (CT), leaf transpiration rate (TRN), intercellular CO2 concentration (INCO); spectral reflectance indices, e.g., Leaf Chlorophyll Index (LCI), curvature index (CI), and normalized difference vegetation index (NDVI); and stress tolerance indices (STI) were determined concurrently with the grain yield. The results revealed significant differences (p ≤ 0.01) among the environments, genotypes, and their interaction for grain yield (GY), days to heading (DH), days to maturity (DM), grain filling period (GFP), grain filling rate (GFR), Normalized difference vegetation index (NDVI), plant height (PH), and spikes per square meter (SM). The genotype plus genotype by environment (GGE) and genotype by yield*trait (GYT) biplot techniques indicated that Genotype 37 (Sakha 95) and Genotype 45 performed best under well-watered and water-deficit environments. Furthermore, the same genotypes were the best from the genotype by stress tolerance indices (GSTI) approach view. Genotype 37 (Sakha 95) was superior to the GYT selection method, with physiological parameters and spectral reflectance indices. Likewise, we can identify this genotype as low-water-tolerant based on GSTI, GYT, and SRI results and recommend involving it in the drought breeding program.

Sparse Phenotyping and Haplotype-Based Models for Genomic Prediction in Rice

The multi-environment genomic selection enables plant breeders to select varieties resilient to diverse environments or particularly adapted to specific environments, which holds a great potential to be used in rice breeding. To realize the multi-environment genomic selection, a robust training set with multi-environment phenotypic data is of necessity. Considering the huge potential of genomic prediction enhanced sparse phenotyping on the cost saving of multi-environment trials (MET), the establishment of a multi-environment training set could also benefit from it. Optimizing the genomic prediction methods is also crucial to enhance the multi-environment genomic selection. Using haplotype-based genomic prediction models is able to capture local epistatic effects which could be conserved and accumulated across generations much like additive effects thereby benefitting breeding. However, previous studies often used fixed length haplotypes composed by a few adjacent molecular markers disregarding the linkage disequilibrium (LD) which is of essential role in determining the haplotype length. In our study, based on three rice populations with different sizes and compositions, we investigated the usefulness and effectiveness of multi-environment training sets with varying phenotyping intensities and different haplotype-based genomic prediction models based on LD-derived haplotype blocks for two agronomic traits, i.e., days to heading (DTH) and plant height (PH). Results showed that phenotyping merely 30% records in multi-environment training set is able to provide a comparable prediction accuracy to high phenotyping intensities; the local epistatic effects are much likely existent in DTH; dividing the LD-derived haplotype blocks into small segments with two or three single nucleotide polymorphisms (SNPs) helps to maintain the predictive ability of haplotype-based models in large populations; modelling the covariances between environments improves genomic prediction accuracy. Our study provides means to improve the efficiency of multi-environment genomic selection in rice.

Mapping and validation of quantitative trait loci associated with dorsal aleurone thickness in rice (Oryza sativa)

Mapping of QTLs for dorsal aleurone thickness (DAT) was performed using chromosome segment substitution lines in rice. Three QTLs, qDAT3.1, qDAT3.2, and qDAT7.1, were detected in multiple environments. As a specified endosperm cell type, the aleurone has an abundance of various nutrients. Increasing the number of aleurone layers is a practicable way of developing highly nutritious cereals. Identifying genes that can increase aleurone thickness is useful for the breeding of aleurone traits to improve the nutritional and health values of rice. Here, we found that iodine staining could efficiently distinguish the aleurone layers, which revealed great variation of the aleurone thickness in rice, especially at the dorsal side of the seed. Therefore, we used a population of chromosome segmental substitution lines (CSSLs) derived from Koshihikari and Nona Bokra for quantitative trait locus (QTL) analysis of the dorsal aleurone thickness (DAT). Three QTLs, qDAT3.1, qDAT3.2, and qDAT7.1, were detected in multiple seasons. Among these, qDAT3.2 colocalizes with Hd6 and Hd16, two QTLs previously identified to regulate the heading date of Koshihikari, explaining the negative correlation between the DAT and days to heading (DTH) in rice. We also provide evidence that early-heading ensures the filling of rice seed under a relatively high temperature to promote aleurone thickening. qDAT7.1, the most stable QTL expressed in different environments, functions independently from heading date. Although Nona Bokra has a lower DAT, its qDAT7.1 allele significantly increased DAT in rice, which was further validated using two near-isogenic lines (NILs). These findings pave the way for further gene cloning of aleurone-related QTLs and may aid the development of highly nutritious rice.

Resilience to Terminal Drought, Heat, and Their Combination Stress in Wheat Genotypes

Heat and drought stresses have negative impacts on wheat yield and growth worldwide, causing up to 60% and 40% yield losses, respectively, but their combined effect can cause severe losses. The present study aimed to identify the high-yielding genetic resources tolerant to drought and/or heat stresses under climate change scenarios. The field trials on 42 genotypes were conducted at three locations in four environments (normal TSIR-NS, drought TSRF-DR, heat LSIR-HT, and heat and drought combined LSRF-DHT) each for two consecutive years. Yield contributing traits were recorded in all the experiments and all the locations: SI (susceptibility index) and STI (stress tolerance index) were also estimated. GY (Grain yield) was severely affected by LSRF-DHT (48.6%), followed by TSRF-DR (23.6%) and LSIR-HT (16.8%). GY had a positive correlation with BM (biomass), HI (harvest index), and TGW (1000-grain weight) under all environments and negative with DH (days to heading) (LSIR-HT and LSRF-DHT). Stepwise regression analysis revealed a higher contribution of BM and HI towards GY under all environments. GW (grain weight/spike) contributed under LSIR-HT and LSRF-DHT, and GN (grain number/spike) under TSIR-NS and TSRF-DR. GFD (grain-filling duration), TGW, and PTL (productive tillers) contributed under all conditions except LSRF-DHT. WS 2016-4 was the only genotype that yielded high under all the conditions. WS 2016-12 and CNM 16-1 were tolerant to heat and drought stresses and high yielding. HINDI 62, HTW 11, and QBP 1606 were less sensitive to all the stresses but low yielding. Overall, out of 30 tolerant genotypes (10 of each category), 19 adapted to escape mechanism which is irrespective of their yielding level. The study demonstrated the potential of identified genotypes in wheat breeding for climate resilience and the traits imparting tolerance to these genotypes.

Genetic Characterization of the Partial Disease Resistance of Rice to Bacterial Panicle Blight and Sheath Blight by Combined QTL Linkage and QTL-seq Analyses.

Bacterial panicle blight (BPB) and sheath blight (SB) are major diseases of rice and few cultivars have shown a high level of resistance to these diseases. A recombinant inbred line (RIL) population developed from the U.S. cultivars Jupiter (moderately resistant) and Trenasse (susceptible) was investigated to identify loci associated with the partial disease resistance to BPB and SB. Disease phenotypes in BPB and SB, as well as the days-to-heading (DTH) trait, were evaluated in the field. DTH was correlated to BPB and SB diseases, while BPB was positively correlated to SB in the field trials with this RIL population. Genotyping was performed using Kompetitive Allele Specific PCR (KASP) assays and whole-genome sequence (WGS) analyses. Quantitative trait locus (QTL) mapping and bulk segregant analysis using a set of WGS data (QTL-seq) detected a major QTL on the upper arm of chromosome 3 for BPB, SB, and DTH traits within the 1.0-1.9 Mb position. Additional QTLs associated with BPB and SB were also identified from other chromosomes by the QTL-seq analysis. The QTLs identified in this study contain at least nine candidate genes that are predicted to have biological functions in defense or flowering. These findings provide an insight into the complex nature of the quantitative resistance to BPB and SB, which may also be closely linked to the flowering trait.

Mapping QTL for Phenological and Grain-Related Traits in a Mapping Population Derived from High-Zinc-Biofortified Wheat.

Genomic regions governing days to heading (DH), days to maturity (DM), plant height (PH), thousand-kernel weight (TKW), and test weight (TW) were investigated in a set of 190 RILs derived from a cross between a widely cultivated wheat-variety, Kachu (DPW-621-50), and a high-zinc variety, Zinc-Shakti. The RIL population was genotyped using 909 DArTseq markers and phenotyped in three environments. The constructed genetic map had a total genetic length of 4665 cM, with an average marker density of 5.13 cM. A total of thirty-seven novel quantitative trait loci (QTL), including twelve for PH, six for DH, five for DM, eight for TKW and six for TW were identified. A set of 20 stable QTLs associated with the expression of DH, DM, PH, TKW, and TW were identified in two or more environments. Three novel pleiotropic genomic-regions harboring co-localized QTLs governing two or more traits were also identified. In silico analysis revealed that the DArTseq markers were located on important putative candidate genes such as MLO-like protein, Phytochrome, Zinc finger and RING-type, Cytochrome P450 and pentatricopeptide repeat, involved in the regulation of pollen maturity, the photoperiodic modulation of flowering-time, abiotic-stress tolerance, grain-filling duration, thousand-kernel weight, seed morphology, and plant growth and development. The identified novel QTLs, particularly stable and co-localized QTLs, will be validated to estimate their effects in different genetic backgrounds for subsequent use in marker-assisted selection (MAS).