Wheat Zone Research Articles

Evaluation of Planting Methods for Rice in Rice-Wheat Zone of Sheikhupura, Pakistan

This study was conducted to evaluate different planting methods for rice crops in the rice wheat zone of Sheikhupura Pakistan for the year 2019-2020. Four planting methods were tested in this study conventional transplanting of rice, 2- Manual transplanting of rice by rope, 3-Mechanical transplanting of rice and 4-Direct seeding of rice. Among all these methods, the mechanical transplanting of rice method proved to perform best in terms of meeting recommended plant population of rice crop, rice crop yield and yield parameters followed by manual transplanting of rice by rope method and direct seeding of rice method. Mechanical transplanting of rice is a mechanized technology for sowing rice crops; solving labor problems and time management. Transplanting of rice by rope method is a laborious method. Direct seeding of rice method also fulfil labour, and plant population issues with proper weeds management, Conventional transplanting of rice method performed poorly in terms of plant population, yield and yield parameters.

Identification of new resistance loci against wheat sharp eyespot through genome-wide association study.

Wheat sharp eyespot caused by Rhizoctonia cerealis is a serious pathogenic disease affecting plants. The effective strategy for controlling this disease is breeding resistant cultivar. However, to date, no wheat varieties are fully resistant to sharp eyespot, and only a few quantitative trait loci (QTLs) have been shown to be associated with sharp eyespot resistance. To understand the genetic basis of this disease, a genome-wide association study (GWAS) of sharp eyespot resistance in 262 varieties from all China wheat regions was conducted. After cultivation for three years, only 6.5% of the varieties were resistant to sharp eyespot. Notably, the varieties from the middle and lower Yangtze River displayed higher sharp eyespot resistance than those from Huanghuai wheat zone. Only two varieties had the same resistance level to the control Shanhongmai. The results of GWAS showed that 5 single nucleotide polymorphism (SNP) loci were markedly related to sharp eyespot resistance in the three years repeatedly, and two QTLs, qSE-6A and qSE-7B, on chromosome 6A and 7B were identified. Based on the 'CG' haplotypes of significant SNPs, we found that the two QTLs exhibited additive effects on attenuating sharp eyespot resistance. These results provide novel insights into the genetic basis of sharp eyespot resistance in China wheat varieties. The SNPs related to sharp eyespot resistance can be applied for marker-assisted selection in plant breeding.

Characterization and distribution of novel alleles of the vernalization gene Vrn-A1 in Chinese wheat (Triticum aestivum L.) cultivars

The ability of wheat to adapt to a wide range of environmental conditions is determined mostly by allelic diversity among genes regulating vernalization requirement. Vrn-1 is a major regulator of this requirement. In this study, two novel alleles of Vrn-A1 were discovered in Chinese cultivars: vrn-A1n was identified in two landraces, Jiunong 2 and Ganchun 16, and Vrn-A1o was detected in Duanhongmangmai. Both novel alleles showed a linked duplication in the promoter region. The common copy of these two alleles was identical to the recessive allele vrn-A1. Compared with the recessive allele vrn-A1, the other copy of vrn-A1n contained a 54-bp deletion in the promoter region and the distinct copy of Vrn-A1o contained an 11-bp deletion in the promoter region. In segregating populations in the greenhouse under nonvernalizing (20–25 °C) and long-day (16 h light) conditions, plants with the novel vrn-A1n allele did not head earlier than those with the recessive vrn-A1 allele. However, plants that were either homozygous or heterozygous for the novel Vrn-A1o allele headed earlier than those with the recessive vrn-A1 allele. To identify the novel allele with the small-sized product and facilitate screening, a DNA marker for the novel dominant allele Vrn-A1o was designed. Analysis of the novel-allele distribution showed that two cultivars carrying the vrn-A1n allele were dispersed in the northwestern spring wheat zone, and 12 cultivars carrying the dominant Vrn-A1o allele were widely distributed in the northwestern spring wheat zone, Xinjiang winter and spring wheat zone, Yellow and Huai River valley winter wheat zone, and Qinghai-Tibetan Plateau spring and winter wheat zone. Our study identifies useful germplasm and a DNA marker for wheat breeding.

Phenotyping winter wheat for early ground cover

The relationship between the early ground cover and the grain yield in winter wheat is not yet fully understood. In a winter wheat breeding programme, selection for early ground cover is traditionally made using visual scoring. Although visual scoring is preferred as a phenotypic screening tool by wheat breeders, its output may not be reliable, as it requires experience. A smartphone camera-based digital image technique can be recommended as a feasible, reliable, repeatable, affordable, and fast selection tool for early ground cover in wheat as an alternative to visual scoring. For this purpose, two wheat trials were conducted in the 2017–2018 and 2019–2020 seasons. In both seasons, 215 wheat genotypes in total, together with three checks from spring wheat, were tested under rain-fed conditions in the spring wheat zone in Turkey. All the tested wheat genotypes were grouped into spring, facultative, and winter growth habit using visual scoring. Simultaneously, photos were taken from each plot with a smartphone camera, and the early ground cover (%) was estimated using the smartphone camera-based digital image technique. The relationships between grain yield, visual scoring, and early ground cover could so be estimated. In both seasons, significant negative correlation between grain yield and visual scoring (r = −0.679** and r = −0.704**, respectively) and significant positive correlation between the grain yield and the early ground cover (r = 0.745** and r = 0.747**, respectively) were observed. The correlation between visual scoring and early ground cover were negative (r = −0.862** and r = −0.926**, respectively). The broad sense heritability estimates in both seasons were 0.51 and 0.85, respectively, for early ground cover, 0.91 and 0.94 for visual scoring, and 0.86 and 0.69 for grain yield. In this study, we revealed that testing winter wheat genotypes in the spring wheat zone rather than in the winter wheat zone could be a more effective way to unveil the positive relationship between the early ground cover and the grain yield. We have shown that the smartphone-based digital image technique is a useful selection tool for early ground cover in winter wheat.

Identification and Validation of Quantitative Trait Loci for Grain Size in Bread Wheat (Triticum aestivum L.)

Grain width (GW) and grain length (GL) are crucial components affecting grain weight. Dissection of their genetic control is essential for improving yield potential in wheat breeding. Yangmai 12 (YM12) and Yanzhan 1 (YZ1) are two elite cultivars released in the Middle and Lower Yangtze Valleys Wheat Zone (MLYVWZ) and the Yellow-Huai River Valleys Wheat Zone (YRVWZ), respectively. One biparental population derived from YM12/YZ1 cross was employed to perform QTL mapping based on the data from four environments over two years to detect quantitative trait loci (QTL) for GW and GL. A total of eight QTL were identified on chromosomes 1B, 2D, 3B, 4B, 5A, and 6B. Notably, QGW.yz.2D was co-located with QGL.yz.2D, and QGW.yz.4B was co-located with QGL.yz.4B, respectively. QGW.yz.2D and QGL.yz.2D, with the increasing GW/GL allele from YZ1, explained 12.36–18.27% and 13.69–26.53% of the phenotypic variations for GW and GL, respectively. QGW.yz.4B and QGL.yz.4B, with the increasing GW/GL allele from YM12, explained 10.34–11.95% and 10.35–16.04% of the phenotypic variation for GW and GL, respectively. QGL.yz.5A, with the increasing GL allele from YM12, explained 10.04–12.48% of the phenotypic variation for GL. Moreover, the positive alleles of these three QTL regions could significantly increase thousand-grain weight, and QGW.yz.4B/QGL.yz.4B and QGL.yz.5A did not show significant negative effects on grain number per spike. QGL.yz.2D, QGW.yz.4B/QGL.yz.4B, and QGL.yz.5A have not been reported. These three QTL regions were then further validated using Kompetitive Allele-Specific PCR (KASP) markers in 159 wheat cultivars/lines from MLYVWZ and YRVWZ. Combining the positive alleles of the major QTL significantly increased GW and GL. Eleven candidate genes associated with encoding ethylene-responsive transcription factor, oleosin, osmotin protein, and thaumatin protein were identified. Three major QTL and KASP markers reported here will be helpful in developing new wheat cultivars with high and stable yields.

Application of <italic>Fhb1 </italic>gene in wheat breeding programs for the Yellow-Huai Rivers valley winter wheat zone of China

<p id="C3"><italic>Fusarium</italic> head blight (FHB), caused by <italic>Fusarium graminearum</italic>, is an important disease that seriously threatens the safety of wheat production. Breeding progress of resistant cultivars has been limited due to absence of the resistant sources with facultative growth habit and poor screening environment in the Huang-Huai region, the main wheat producing area of China. <italic>Fhb1</italic>, as the most effective and stable gene, is the only gene widely used in the global breeding programs for improving FHB resistance of wheat. However, utilization of <italic>Fhb1</italic> in the Yellow-Huai River Valleys Winter Wheat Zone is limited so far. In this study, several excellent advanced lines with <italic>Fhb1</italic> were developed by limited backcrossing and molecular marker-assisted selection in the BC₂F₁ progenies of the susceptible variety Aikang 58 (the recurrent parent) and H35 (the donor parent of <italic>Fhb1</italic> gene). Then, the individuals were used to cross with Xumai 36 and Xumai 2023 (with high yield but susceptible to FHB), and a series of elite lines with <italic>Fhb1</italic> were developed using the doubled haploid and the traditional pedigree selection methods. Xumai DH9 and Xumai 17252 were moderate resistance to FHB in different screening environments for several years. The average resistance level of the lines with <italic>Fhb1</italic> gene was significantly higher than that of the susceptible control. The introduction of <italic>Fhb1</italic> significantly improved the resistance to FHB, but some lines were still highly susceptible, indicating that the resistance to FHB was affected by other genetic factors. This study provides an example for the use of <italic>Fhb1</italic> gene in improving FHB resistance in the Yellow-Huai River Valleys Winter Wheat Zone of China.

TaERF73 is associated with root depth, thousand‐grain weight and plant height in wheat over a range of environmental conditions

AbstractAP2/ERF is a plant‐specific transcription factor superfamily regulating plant growth, development and responses to multiple stresses. However, the roles of ERF genes in the growth and development of wheat (Triticum aestivum L.) remain elusive. In this study, a novel ERF gene TaERF73 was cloned from wheat. qRT‐PCR analysis showed that TaERF73 is predominantly expressed in roots. It responds to treatments of auxin, MeJA, ABA, low temperature and drought stresses. Ectopic expression of TaERF73 in rice caused short root length, indicating that TaERF73 is a negative regulator of root growth. Four SNPs were detected in TaERF73‐4B coding region through sequence polymorphism analysis. A dCAPS (derived cleaved amplified polymorphic sequence) molecular marker was developed based on the SNP at 119 bp (G/C) of TaERF73‐4B. Association analysis between genotypes and agronomic traits revealed that Hap‐4B‐2 is a haplotype of TaERF73‐4B associated with shorter plant height, higher thousand‐grain weight and longer root depth. The distributions of haplotypes in ten Chinese major wheat zones suggested that Hap‐4B‐2 has been positively selected in the breeding process. Together, the ERF gene TaERF73 is associated with root depth, plant height and thousand‐grain weight under drought, heat and well‐watered conditions. The molecular marker developed in this study could be a valuable source for marker‐assisted selection and genetic improvement in wheat.

High-temperature wheat leaf rust resistance gene Lr13 exhibits pleiotropic effects on hybrid necrosis

High-temperature wheat leaf rust resistance gene Lr13 exhibits pleiotropic effects on hybrid necrosis

Winter Wheat Adaptation to Climate Change in Turkey

Climate change scenarios reveal that Turkey’s wheat production area is under the combined effects of heat and drought stresses. The adverse effects of climate change have just begun to be experienced in Turkey’s spring and the winter wheat zones. However, climate change is likely to affect the winter wheat zone more severely. Fortunately, there is a fast, repeatable, reliable and relatively affordable way to predict climate change effects on winter wheat (e.g., testing winter wheat in the spring wheat zone). For this purpose, 36 wheat genotypes in total, consisting of 14 spring and 22 winter types, were tested under the field conditions of the Southeastern Anatolia Region, a representative of the spring wheat zone of Turkey, during the two cropping seasons (2017–2018 and 2019–2020). Simultaneous heat (&gt;30 °C) and drought (&lt;40 mm) stresses occurring in May and June during both growing seasons caused drastic losses in winter wheat grain yield and its components. Declines in plant characteristics of winter wheat genotypes, compared to those of spring wheat genotypes using as a control treatment, were determined as follows: 46.3% in grain yield, 23.7% in harvest index, 30.5% in grains per spike and 19.4% in thousand kernel weight, whereas an increase of 282.2% in spike sterility occurred. On the other hand, no substantial changes were observed in plant height (10 cm longer than that of spring wheat) and on days to heading (25 days more than that of spring wheat) of winter wheat genotypes. In general, taller winter wheat genotypes tended to lodge. Meanwhile, it became impossible to avoid the combined effects of heat and drought stresses during anthesis and grain filling periods because the time to heading of winter wheat genotypes could not be shortened significantly. In conclusion, our research findings showed that many winter wheat genotypes would not successfully adapt to climate change. It was determined that specific plant characteristics such as vernalization requirement, photoperiod sensitivity, long phenological duration (lack of earliness per se) and vulnerability to diseases prevailing in the spring wheat zone, made winter wheat difficult to adapt to climate change. The most important strategic step that can be taken to overcome these challenges is that Turkey’s wheat breeding program objectives should be harmonized with the climate change scenarios.

Investigation of Farmland Soil and Wheat Heavy Metal Contamination Character in Jinding of Lanping

The contents of Cd and Pb in soil and wheat in Jinding of Lanping in Yunnan were investigated and sampled. And single pollution index method, comprehensive pollution index method and correlation analysis were used to evaluate heavy metal contamination in wheat and soil. Zone A is in the upper reaches of the Pijiang River, and the zone does not contain large mines, where soil in the farmland is not polluted by the heavy metals Cd and Pb. The soil in zone B is slightly polluted by Cd and Pb, and the over-standard rate of the Cd of the samples measured is 75%, and the over-standard rate of the Pb of the soil is 25%. The condition of soil polluted by two heavy metals is Cd > Pb, and the heavy metal pollution of the soil in this Zone is mainly affected by mining activities. Zone C is in the lower reaches of the Pijiang River, and the soil in Zone C is not polluted by Cd and Pb. The content of Cd and Pb in the wheat in Zone A reached the standard and was not polluted. The wheat in Zone B was not polluted by Cd and Pb. Although Cd and Pb in the soil in this Zone was over-standard, it could be concluded that Cd and Pb in the soil did not migrate to wheat. The wheat in Zone C was not contaminated by Cd and Pb.

Genome-wide association mapping reveals potential novel loci controlling stripe rust resistance in a Chinese wheat landrace diversity panel from the southern autumn-sown spring wheat zone

BackgroundStripe rust, caused by the fungal pathogen Puccinia striiformis f. sp. tritici (Pst), is a serious foliar disease of wheat. Identification of novel stripe rust resistance genes and cultivation of resistant cultivars are considered to be the most effective approaches to control this disease. In this study, we evaluated the infection type (IT), disease severity (DS) and area under the disease progress curve (AUDPC) of 143 Chinese wheat landrace accessions for stripe rust resistance. Assessments were undertaken in five environments at the adult-plant stage with Pst mixture races under field conditions. In addition, IT was assessed at the seedling stage with two prevalent Pst races (CYR32 and CYR34) under a controlled greenhouse environment.ResultsSeventeen accessions showed stable high-level resistance to stripe rust across all environments in the field tests. Four accessions showed resistance to the Pst races CYR32 and CYR34 at the seedling stage. Combining phenotypic data from the field and greenhouse trials with 6404 markers that covered the entire genome, we detected 17 quantitative trait loci (QTL) on 11 chromosomes for IT associated with seedling resistance and 15 QTL on seven chromosomes for IT, final disease severity (FDS) or AUDPC associated with adult-plant resistance. Four stable QTL detected on four chromosomes, which explained 9.99–23.30% of the phenotypic variation, were simultaneously associated with seedling and adult-plant resistance. Integrating a linkage map of stripe rust resistance in wheat, 27 QTL overlapped with previously reported genes or QTL, whereas four and one QTL conferring seedling and adult-plant resistance, respectively, were mapped distantly from previously reported stripe rust resistance genes or QTL and thus may be novel resistance loci.ConclusionsOur results provided an integrated overview of stripe rust resistance resources in a wheat landrace diversity panel from the southern autumn-sown spring wheat zone of China. The identified resistant accessions and resistance loci will be useful in the ongoing effort to develop new wheat cultivars with strong resistance to stripe rust.

АРГУМЕНТЫ ПОЧВОЗАЩИТНОЙ ТЕХНОЛОГИИ ВЫРАЩИВАНИЯ КУЛЬТУР В ЗОНЕ НЕДОСТАТОЧНОГО УВЛАЖНЕНИЯ

In the article we show arguments for achieving the research goal- to get economically feasible crop yield growth of sunflower , spring barley and winter wheat in zone of low moisture of Rostov region against common and soil protective technology. The experiment was two-factorial: factor А – crop rotation link, factor B – crop cultivation technology. Soil protective technology with after harvesting and plant residues on soil surface affected moisture collection and conservation in soil at the cost of best preservation of snow cover, decrease of aeration. Soil protective technology allowed to preserve in the field from 84,5 to 95,1 % of plant residues, which increased show cover for 16,5-28,4%. Significant impact on soil density soil protective technology didn’t demonstrate. Compared to common, it helped to increase the number of earthworms in 4,3 times, which is the evidence of environmentally safe soil quality. Influence of soil protective technology on field emergence of studied cultures is established. Survival of cereal crops was higher for 2-5 %, and sunflower was lower for 5,4 %. All the cultures increased crop yield when using soil protective technology. Effect of transition to soil protective technology grew from year to year. Profitability raised in the first year for 11%, in the second for 13%, in the third for 36%. Spring barley and sunflower showed big response on this technology. Introduction of soil protective technology in average in years of experiments improved profitability for 20 %.

Genome-wide association analysis of stem water-soluble carbohydrate content in bread wheat.

GWAS identified 36 potentially new loci for wheat stem water-soluble carbohydrate (WSC) contents and 13 pleiotropic loci affecting WSC and thousand-kernel weight. Five KASP markers were developed and validated. Water-soluble carbohydrates (WSC) reserved in stems contribute significantly to grain yield (GY) in wheat. However, knowledge of the genetic architecture underlying stem WSC content (SWSCC) is limited. In the present study, 166 diverse wheat accessions from the Yellow and Huai Valleys Winter Wheat Zone of China and five other countries were grown in four well-watered environments. SWSCC at 10 days post-anthesis (10DPA), 20DPA and 30DPA, referred as WSC10, WSC20 and WSC30, respectively, and thousand-kernel weight (TKW) were assessed. Correlation analysis showed that TKW was significantly and positively correlated with WSC10 and WSC20. Genome-wide association study was performed on SWSCC and TKW with 373,106 markers from the wheat 660K and 90K SNP arrays. Totally, 62 stable loci were detected for SWSCC, with 36, 24 and 19 loci for WSC10, WSC20 and WSC30, respectively; among these, 36 are potentially new, 16 affected SWSCC at two or three time-points, and 13 showed pleiotropic effects on both SWSCC and TKW. Linear regression showed clear cumulative effects of favorable alleles for increasing SWSCC and TKW. Genetic gain analyses indicated that pyramiding favorable alleles of SWSCC had simultaneously improved TKW. Kompetitive allele-specific PCR markers for five pleiotropic loci associated with both SWSCC and TKW were developed and validated. This study provided a genome-wide landscape of the genetic architecture of SWSCC, gave a perspective for understanding the relationship between WSC and GY and explored the theoretical basis for co-improvement of WSC and GY. It also provided valuable loci and markers for future breeding.

Does any phenological event defined by remote sensing deserve particular attention? An examination of spring phenology of winter wheat in Northern China

Phenology is often considered the “leading indicator” of ecological responses to climate change, and therefore it is important that researchers have accurate methods to track phenological changes. Remote sensing has been widely used to study phenological responses to climate change. However, land surface phenology observed by remote sensing is fundamentally different from that observed in the field, which raises the difficulty in understanding and validating phenological change observed using remote sensing. In this study, we revisited the criteria of “good” phenological events and argued that the relationship between phenology and climate factors is one of the most important meanings of phenological studies. Instead of validating remotely sensed phenology by its consistency with field observations, this study aims to judge different possible definitions of phenological events based on remote sensing by their temperature sensitivity and correlation. Using the winter wheat zone in northern China as the study area, we compared the temperature correlation and sensitivities of winter wheat phenology date derived from different methods: the relative threshold method with different thresholds, and the curvature method, based on remotely sensed data. Our results show that there is no distinct phenological event that is overwhelmingly more sensitive or correlative than any others. Therefore, there are no particular phenological events that deserve emphasis when exploring the relationship between phenology date and the pre-season temperature. Instead, the phenological stage (i.e. the threshold of relative threshold method) that is most sensitive or correlative to pre-season temperature varies spatially, showing a good latitude gradient. On an average, the thresholds of the most correlative and sensitive phenological stages to pre-season temperature decreased by 9.92% and 14.69% per latitudinal degree, respectively. The results indicate that the traditional emphasis on discrete phenological events could miss the phenological stages that are most sensitive and correlative to pre-season temperature, thereby resulting in a limited understanding of phenological responses to climate change.

Genetic progress in stem lodging resistance of the dominant wheat cultivars adapted to Yellow-Huai River Valleys Winter Wheat Zone in China since 1964

Analysis of genetic progress for lodging-related traits provides important information for further improvement of lodging resistance. Forty winter wheat cultivars widely grown in the Yellow-Huai River Valleys Winter Wheat Zone (YHWZ) of China during the period of 1964–2015 were evaluated for several lodging-related traits in three cropping seasons. Plant height, height at center of gravity, length of the basal second internode, and lodging index decreased significantly in this period, and the average annual genetic gains for these traits were −0.50 cm or −0.62%, −0.27 cm or −0.60%, −0.06 cm or −0.63%, and −0.01 or −0.94%, respectively. Different from other traits, stem strength showed a significant increasing trend with the breeding period, and the annual genetic gains were 0.03 N or 0.05%. Correlation analysis showed that lodging index was positively correlated with plant height, height at center of gravity, and length of the basal second internode, but negatively correlated with stem strength. Meanwhile, significantly positive correlations were observed between plant height, height at center of gravity, and length of the basal first and second internodes. By comparison with the wild types, dwarfing genes had significant effects on all lodging-related traits studied except for length of the basal first internode and stem strength. Principle component analysis demonstrated that plant height and stem strength were the most important factors influencing lodging resistance. Clustering analysis based on the first two principle components further indicated the targets of wheat lodging-resistant breeding have changed from reducing plant height to strengthening stem strength over the breeding periods. This study indicates that the increase of stem strength is vital to improve lodging resistance in this region under the high-yielding condition when plant height is in an optimal range.

Comparison of water use efficiency, profitability and consumer preferences of different rice varieties in Punjab, Pakistan

Due to rapid population growth, water scarcity and food insecurity have become the major problems for Pakistan. Therefore, the efficient utilization of limited resources such as water is very important in agriculture. Paddy or rice—Pakistan’s second most important cereal and staple crop—is a water-intensive crop. The present study aims to estimate the water use efficiency, profitability, and consumer preferences of different paddy varieties such as basmati, coarse and hybrid rice in Punjab. To this end, we collected field survey data from 330 rice growers in six districts of the rice–wheat zone of Punjab. The results showed that basmati rice is more profitable due to low production cost and higher prices. Although the number of irrigations applied to basmati rice and coarse rice was higher than that of hybrid rice, the amount of water applied to hybrid rice was the highest. Therefore, the total irrigation cost of hybrid rice is higher, while the coarse rice has higher water productivity. Furthermore, the economic productivity of water applied to basmati rice and coarse rice is higher than that of hybrid rice. Consumer preferences based on data from 150 consumers indicate that basmati rice is a favorite of consumers and that hybrid rice is the least popular. These results imply that it is better to grow basmati or coarse rice than hybrid rice due to water shortages in Pakistan. Another approach is to replace these varieties with alternative crops such as corn and soybeans that require less water.

Phylogenetic and population structural inference from genomic ancestry maintained in present-day common wheat Chinese landraces.

Hexaploid common wheat is one of the most important food crops worldwide. Common wheat domestication began in the Fertile Crescent of the Near East approximately 10000years ago and then spread west into Europe and eastward into East Asia and China. However, the possible spreading route into and within China is still unclear. In this study, we successfully extracted DNA from single ancient wheat seeds and sequenced the whole genome of seven ancient samples from Xiaohe and Gumugou cemeteries in Xinjiang, China. Genomic inference and morphological observation confirmed their identity as hexaploid common wheat grown in prehistoric China at least 3200years before present (BP). Phylogenetic and admixture analyses with RNA-seq data of modern hexaploid wheat cultivars from both China and Western countries demonstrated a close kinship of the ancient wheat to extant common wheat landraces in southwestern China. The highly similar allelic frequencies in modern landraces of the Qinghai-Tibetan plateau with the ancient wheat support the previously suggested southwestern spreading route into highland China. A subsequent dispersal route from the Qinghai-Tibetan plateau margins to the Yangtze valley was proposed in this study. Furthermore, the common wheat populations grown in the Middle and Lower Yangtze valley wheat zones were also proposed to be established by population admixture with the wheat grown in the Upper Yangtze valley. Our study reports ancient common wheat sequences at a genome-wide scale, providing important information on the origin, dispersal, and genetic improvement under cultivation of present-day wheat landraces grown in China.

Effects of the Fhb1 gene on Fusarium head blight resistance and agronomic traits of winter wheat

The gene Fhb1 has been used in many countries to improve wheat Fusarium head blight (FHB) resistance. To make better use of this gene in the Yellow-Huai River Valleys Winter Wheat Zone (YHWZ), the most important wheat-producing region of China, it is desirable to elucidate its effects on FHB resistance and agronomic traits in different genetic backgrounds. Based on a diagnostic marker for Fhb1, six BC2 populations were developed by crossing dwarf-male-sterile (DMS)-Zhoumai 16 to three Fhb1 donors (Ningmai 9, Ningmai 13, and Jianyang 84) and backcrossing to Zhoumai 16 and Zhoumai 16's derivative cultivars (Lunxuan 136 and Lunxuan 13) using marker-assisted backcross breeding. The progenies were assessed for FHB resistance and major agronomic traits. The Fhb1 alleles were identified using the gene-specific molecular marker. The plants with the Fhb1-resistant genotype (Fhb1-R) in these populations showed significantly fewer infected spikelets than those with the Fhb1-susceptible genotype (Fhb1-S). When Lunxuan 136 was used as the recurrent parent, Fhb1-R plants showed significantly fewer infected spikelets per spike than Fhb1-R plants produced using Lunxuan 13 as the recurrent parent, indicating that the genetic backgrounds of Fhb1 influence the expression of FHB resistance. Fhb1-R plants from the DMS-Zhoumai 16/Ningmai 9//Zhoumai 16/3/Lunxuan 136 population showed the highest FHB resistance among the six populations and a significantly higher level of FHB resistance than the moderately susceptible control Huaimai 20. No significant phenotypic differences between Fhb1-R and Fhb1-S plants were observed for the eight agronomic traits investigated. These results suggest that it is feasible to improve FHB resistance of winter wheat without reducing yield potential by introgressing Fhb1 resistance allele into FHB-susceptible cultivars in the YHWZ.

Genetic architecture of grain yield in bread wheat based on genome-wide association studies

BackgroundIdentification of loci for grain yield (GY) and related traits, and dissection of the genetic architecture are important for yield improvement through marker-assisted selection (MAS). Two genome-wide association study (GWAS) methods were used on a diverse panel of 166 elite wheat varieties from the Yellow and Huai River Valleys Wheat Zone (YHRVWD) of China to detect stable loci and analyze relationships among GY and related traits.ResultsA total of 326,570 single nucleotide polymorphism (SNP) markers from the wheat 90 K and 660 K SNP arrays were chosen for GWAS of GY and related traits, generating a physical distance of 14,064.8 Mb. One hundred and twenty common loci were detected using SNP-GWAS and Haplotype-GWAS, among which two were potentially functional genes underpinning kernel weight and plant height (PH), eight were at similar locations to the quantitative trait loci (QTL) identified in recombinant inbred line (RIL) populations in a previous study, and 78 were potentially new. Twelve pleiotropic loci were detected on eight chromosomes; among these the interval 714.4–725.8 Mb on chromosome 3A was significantly associated with GY, kernel number per spike (KNS), kernel width (KW), spike dry weight (SDW), PH, uppermost internode length (UIL), and flag leaf length (FLL). GY shared five loci with thousand kernel weight (TKW) and PH, indicating significantly affected by two traits. Compared with the total number of loci for each trait in the diverse panel, the average number of alleles for increasing phenotypic values of GY, TKW, kernel length (KL), KW, and flag leaf width (FLW) were higher, whereas the numbers for PH, UIL and FLL were lower. There were significant additive effects for each trait when favorable alleles were combined. UIL and FLL can be directly used for selecting high-yielding varieties, whereas FLW can be used to select spike number per unit area (SN) and KNS.ConclusionsThe loci and significant SNP markers identified in the present study can be used for pyramiding favorable alleles in developing high-yielding varieties. Our study proved that both GWAS methods and high-density genetic markers are reliable means of identifying loci for GY and related traits, and provided new insight to the genetic architecture of GY.

Historical genetic responses of yield and root traits in winter wheat in the yellow-Huai-Hai River valley region of China due to modern breeding (1948–2012)

The Yellow and Huai Valleys Winter Wheat Zone (YHVWWZ) is the predominant wheat-producing region in China. This study aimed to identify genetic gains in root characteristics and grain yield of winter wheat (Triticum aestivum L.) cultivars to assist future breeding strategies. Field trials were conducted in the wetter-than-average 2014–2015 and drier-than-average 2015–2016 growing seasons. Yield and related traits were measured in 17 wheat cultivars released for irrigated conditions in the YHVWWZ from 1948 to 2012. Yields have increased in the 60 years of breeding and selection of cultivars in this region. No change in root biomass with year of release was evident in 2014–2015, but it increased significantly in 2015–2016. The density of shallow roots (0–1 m) increased significantly with year of release in both seasons, while the density of deeper roots (1–2 m) decreased significantly in 2014–2015 and increased significantly in 2015–2016. Aboveground biomass increased with year of release in 2014–2015 but did not change in 2015–2016, and total biomass (root plus shoot) increased with year of release in both seasons. Modern wheat cultivars are better adapted to different watering levels in irrigated areas than older cultivars, with more root biomass at shallow depth, higher plasticity of the root system with depth, and increased yields.