World Wheat Production Research Articles

POSTULATION OF YR RESISTANCE GENES TO STRIPE RUST IN 12 COMMERCIAL WHEAT CULTIVARS OF RUSSIAN BREEDING

Stripe rust (Puccinia striiformis f. sp. tritici) is a common wheat disease of economic importance in all world wheat production regions. In most of the regions stripe rust causes yield losses of 10-70 %, depending on the time infection occur, host susceptibility, disease development, and the duration of the epidemics. In South Russia even in unfavourable conditions for the pathogen, stripe rust occurred in the region every year, and in some areas there are foci of the disease with of up to 50% severity.
 Phytopathological testing is one of the least expensive and most effective methods for the rapid identification of juvenile resistance genes in varieties against pathogens. It allows to obtain detailed information about the genetics of the host and pathogen in a short time. In the research Yr resistant genes and its combinations were postulated in winter wheat varieties of Russian breeding to North-Caucasus population of stripe rust by this method.
 Purpose of this study was identification of known stripe rust resistance genes in 12 commercial winter wheat cultivars by phytopathological testing.
 Material and methods: The postulation of known resistance genes was carried out in a greenhouse complex (seedling stage) and at the research station (adult plant stage) of the Laboratory of Plant Immunity to Diseases of the Federal Scientific Center for Biological Plant Protection (Krasnodar).
 For postulation, we chose the method by Dubin et al. (1989), based on the comparison of response types of differential cultivars and studied varieties to Pst isolates.
 Results. In 10 out of 12 winter wheat varieties of Russian breeding, 13 stripe rust resistance genes and their combinations were postulated.: Yr3, Yr3a, Yr6, Yr32, Yr2+6, Yr2+9, Yr39+Alp, Yr4+12, Yr4b, Yr3a+4a+H46, YrA, YrSp, YrSU. The following resistance genes have not been identified: Yr2, Yr5, Yr10, Yr10+Mor, Yr24, Yr27, Yr25+32, since no isolates virulent to carriers of these genes were isolated from the North Caucasian population of P. striiformis; and they are highly effective against this population. Highly effective (Yr3, Yr2+9, Yr3a, Yr4+12, Yr3a+4a+H46) resistance genes were identified in the Kurs, Morozko, and Step’ varieties. We note a combination of effective Yr2+6 genes in the Gurt variety.
 In field conditions, high resistance (degree of damage up to 10%) to the North Caucasian population of the stripe rust pathogen was shown by lines and differential cultivars containing the following resistance genes: Yr2, Yr3, Yr8, Yr10, Yr24, Yr25, Yr27, Yr10+Mor, Yr3a, Yr25+32, Yr3a+4a+H46, Yr3с+Min, Yr4+12, Yr7+25, Yr8+19, 8+6+25, YrSp. Due to the low degree of damage, these genes and their combinations are classified as highly effective and can be involved in the breeding process to create new resistant varieties. Varieties containing these genes can also be recommended for breeders and used in production for effective disease control.

Wojna w Ukrainie jako determinanta zmian w zachowaniach konsumenckich w Polsce i na świecie. Przykład rynków żywnościowych, nieruchomości oraz dóbr luksusowych

The war in Ukraine and global inflation are currently having a direct impact on the consumer behavior of both Poles and people around the world. This is confirmed by a number of research reports and statistical data. One can also observe this phenomenon in macroeconomic indi- cators. Ukraine is an important agricultural basin (including 10% of world wheat production and 50% of sunflower oil production), and Russia is blocking grain supplies through Ukrainian ports on the Black Sea. This supply glut is particularly felt in countries dependent on imports of Ukrainian grain and cooking oil, such as Egypt and India. The European real estate market, initially resistant to inflation and the war in Ukraine, is also starting to become more dynamic. Demand for luxury goods in Europe and the United States is growing despite a confluence of many negative factors that would seem expected to spoil consumer sentiment. The article will outline significant changes in consumer behavior with regard to the food, real estate and luxury goods markets, which represent the need for both companies’ marketing efforts and their sales strategies and consumers themselves to adapt to the “new” economic and social reality.

Source Identification and Genome-Wide Association Analysis of Crown Rot Resistance in Wheat.

Crown rot (CR) is a soil-borne disease of wheat in arid and semiarid areas of the world. The incidence rate and severity of CR are increasing with each passing year, which seriously threatens the safety of world wheat production. Here, 522 wheat varieties/lines representing genetic diversity were used to identify and evaluate the resistance source to CR disease. Six varieties, including Zimai 12, Xinong 509, Mazhamai, Sifangmai, and Dawson, were classified as resistant ® to CR. Seventy-nine varieties were classified as moderately resistant (MR) to CR, accounting for 15.13% of the tested varieties. The wheat 660 K SNP array was used to identify resistance loci by genome-wide association analysis (GWAS). A total of 33 SNPs, located on chromosomes 1A, 1B, 1D, 4A, and 4D, were significantly correlated with seedling resistance to CR in two years. Among them, one SNP on chromosome 1A and nine SNPs on chromosome 1B showed most significant resistance to disease, phenotypic variance explained (PVE) by these SNPs were more than 8.45%. Except that significant locus AX-110436287 and AX109621209 on chromosome 1B and AX-94692276 on 1D are close to the already reported QTL, other SNPs are newly discovered resistance loci. These results could lay a strong theoretical foundation for the genetic improvement and breeding for CR resistance in wheat.

Macro- and Microscopic Characterization of Components of Resistance against Puccinia striiformis f. sp. tritici in a Collection of Spanish Bread Wheat Cultivars

Yellow (stripe) rust, caused by the biotrophic fungus Puccinia striiformis f. sp. tritici (Pst), stands as the most serious wheat disease worldwide, affecting approximately 88% of world wheat production. Even though yellow rust generally develops in cool humid weather conditions, the expansion of new races adapted to warmer climates threatens zones where severe P. striiformis epidemics were infrequent, such as Andalusian wheat cropping areas. In order to characterize yellow rust resistance mechanisms in Spanish germplasm, our study evaluated 19 Spanish bread wheat cultivars against P. striiformis under controlled conditions for percentage of disease severity (DS) and infection type (IT). From this visual evaluation, 74% of evaluated cultivars showed resistant responses against P. striiformis infection with only five cultivars considered susceptible. Subsequently, macroscopic and microscopic components of resistance were identified through image analysis and histological studies, respectively, in six selected cultivars. Macroscopic parameters such as total pustule area and total affected area (%), together with microscopic parameters such as early-aborted and established microcolonies regarding plant cell death responses (%), and microcolony length (µm), were identified as capable of differentiating cultivars quantitatively. Thus, these parameters could be used as a basis for screening resistant responses in future breeding programs, complementary to physiology, genetic and biochemical studies of plant-Pst interaction. Finally, our study seems to be the first macroscopic and microscopic characterization of P. striiformis infection in a collection of Spanish bread wheat cultivars in controlled conditions.

Prediction of wheat quality parameters combining Raman, fluorescence, and near‐infrared spectroscopy (NIRS)

AbstractBackground and ObjectivesA high amount of the world wheat production is used for bread making. Due to its simplicity, wheat samples are traded based on protein content, although this is only an indirect measurement of baking quality. As direct bread quality traits like loaf volume, water absorption, and dough properties are cumbersome to measure along wheat supply chains and in wheat breeding programs, this study aims to predict directly dough properties and baking behavior by combining complementary information from near‐infrared, Raman, and fluorescence spectroscopy. Several proven data preprocessing and regression algorithms were evaluated, including partial least‐squares regression (PLSR) and genetic algorithm (GA).FindingsA highly diverse sample set of 415 wheat samples from a wheat hybrid breeding program was analyzed as whole grain, whole grain flour, and extracted flour. The best predictive models yielded a 10‐fold cross‐validated coefficient of determination R2 of .973, .873, .774, .835, .369, .447, .311, .512, .536, .723, and .715 for protein content, wet gluten, loaf volume, water uptake, elongation resistance to extension, extensibility, ratio number, extensograph energy, maltose number, plant height, and grain yield, respectively.ConclusionThe prediction accuracies are well suited for screening purposes in wheat breeding and allow better quality assessment compared to protein content along wheat supply chains.Significance and NoveltyIn this study, complementary spectroscopic techniques are combined for the first time to achieve higher prediction accuracy for a wide range of wheat quality parameters. In addition, Raman and fluorescence spectroscopy were used to predict quality data from a large sample set.

Yield potential of world wheat based on ARIMA model under global warming

As the most important food crop across the world, with continuous increase in world population and steady declining farmlands, wheat has been attracting academic attention for improving its yield or potential in the future particularly under global warming. Therefore, analyzing the yield or potential of wheat at global level relevant to greenhouse gas effect is of great significance to direct future production of wheat in the world. However up to now, there are relatively few reports on potential yield of world wheat projected using ‘time series’ approach like ARIMA (Auto-regressive Integrated Moving Average) model. Thus in this paper, the crop potential yield of world wheat during 2019 to 2028 is projected using ARIMA model based on the yields from 1961 to 2018. Our results show that during 2019 to 2028, the average yields of world wheat are projected to increase from 3569 to 4257 kg ha-1 while top yields of world wheat from 9852 to 11246 kg ha-1. Annual global mean temperatures are projected to increase from 15.05 to 15.31°C. Global warming exerts positive effect on average yield of world wheat while negative effect on the top yield in 1961 to 2018 and 2028. Our study concluded that for world wheat production in 2019 to 2028, the opportunities for improving production should be mainly dependent on the advantage of highyield countries as the yield is still in low place before the turn-point of S-shaped curve in long-term trend affected partly by greenhouse gas effect.

EFFECTS OF TERMINAL HEAT STRESS AND THEIR RESPONSIVE MECHANISMS IN ELITE WHEAT GENOTYPES: A REVIEW

Wheat is the most important cereal crop in the world that ranks first position in terms of production and trade. In Nepal this is the third most cultivated crop after rice and maize. Various environmental constraints including heat stress have been determined to be a great factor to limit world wheat production. High temperature leaves a devastating impact in wheat production by affecting different stages including germination, plant growth, anthesis and grain filling etc. heat stress also affects photosynthesis process and responsible for the lower biomass yield. Various studies have shown that the reproductive stages of wheat plant are more susceptible to heat stress than vegetative stages. Heat stress hinders germination, reduce plant growth, decrease number of plant population per unit area and causes leaf senescence. Water relation disturbance and oxidative damage to plants are other harmful effects of heat stress in wheat plants. Plant also has tolerance mechanism against such heat induced stresses. Such mechanisms include avoidance against heat stress, production of heat shock protein and antioxidant mechanisms.

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

Genetic Dissection of Adult Plant Resistance to Sharp Eyespot Using an Updated Genetic Map of Niavt14 × Xuzhou25 Winter Wheat Recombinant Inbred Line Population.

Wheat sharp eyespot, a disease mainly caused by soilborne fungus Rhizoctonia cerealis, is a threat to world wheat production. Wheat's genetic resistance to sharp eyespot is a potential approach to reducing the application of fungicides and farming practice inputs. To identify the genetic basis of sharp eyespot resistance in Niavt14, a recombinant inbred line population comprising 215 F8 lines from Niavt14 × Xuzhou25, was developed. An earlier linkage map (148 simple sequence repeat markers) was updated with 5,792 polymorphic Affymetrix Axiom 55K single-nucleotide polymorphisms to a new map of 5,684.2 centimorgans with 1,406 nonredundant markers. The new linkage map covered all 21 chromosomes of common wheat and showed a good collinearity with the IWGSC RefSeq v1.0 genome. We conducted quantitative trait locus (QTL) mapping for sharp eyespot resistance using the adult plant response data from the field of five consecutive growing seasons and one greenhouse test. Two stable QTL on chromosomes 2B and 7D that were identified in the previous study were confirmed, and three novel, stable QTL, explaining 4.0 to 17.5% phenotypic variation, were mapped on 1D, 6D, and 7A, which were independent of QTL for phenology and plant height. The QTL on 1D, 2B, 6D, and 7A showed low frequencies in 384 landraces (0 to 10%) and 269 elite cultivars (5 to 23%) from the southern winter wheat region and the Yellow and Huai River Valley facultative wheat region in China, respectively. These identified QTL could be used in wheat breeding programs for improving sharp eyespot resistance through marker-assisted selection.

Inheritance of leaf rust resistance in four popular Indian durum wheat cultivars

Leaf rust is the one of the most important biotic stresses affecting world wheat production because of its wide distribution. In a study conducted to understand the inheritance of leaf rust resistance genes present in the popular durum wheat cultivars viz. HI 8498, HI 8663, HI 8713 and HI 8737 indicated that a single dominant gene each controls resistance to two Puccinia triticina (Pt) pathotypes 162-2 (93R39) and 104-2 (21R55). The allelic tests indicated that three diverse genes control resistance to Pt pathotype 104-2, with the gene being common between HI 8713 and HI 8737. Resistance to pathotype 162-2 was controlled by two diverse genes among the four test cultivars as the same gene conditioned resistance in HI 8737, HI 8713 and HI 8663 with the resistance gene in HI 8498 being different. The infection types of the two Pt pathotypes on the test cultivars were found to be higher than that of near isogenic lines carrying Lr3, Lr14a and Lr23 indicating that the identified genes in the present study were different from these commonly postulated Lr genes in Indian durum germplasm. The identified leaf rust resistance genes in the study will contribute to the diversity of leaf rust resistance in durum wheat and can be well utilized in breeding programmes.

Molecular Marker Based Design for Breeding Wheat Lines with Multiple Resistance and Superior Quality.

There has not been a major wheat stem rust epidemic worldwide since the 1970s, but the emergence of race TTKSK of Puccinia graminis f. sp. tritici in 1998 presented a great threat to the world wheat production. Single disease-resistance genes are usually effective for only several years before the pathogen changes genetically to overcome the resistance. Stripe rust caused by Puccinia striiformis f. sp. tritici (Pst) is one of the most common and persistent wheat diseases worldwide. The development of varieties with multiple resistance is the most economical and effective strategy for preventing stripe rust and stem rust, the two main rust diseases constraining wheat production. Plateau 448 has been widely used in the spring wheat growing region in northwest China, but it has become susceptible to stripe rust and is susceptible to TTKSK. To produce more durable resistance to race TTKSK as well as to stripe rust, four stem rust resistance genes (Sr33, Sr36, Sr-Cad, and Sr43) and three stripe rust resistance genes (Yr5, Yr18, and Yr26) were simultaneously introgressed into Plateau 448 to improve its stem rust (Ug99) and stripe rust resistance using a marker-assisted backcrossing strategy combined with phenotypic selection. We obtained 131 BC1F5 lines that pyramided two to four Ug99 resistance genes and one to two Pst resistance genes simultaneously. Thirteen of these lines were selected for their TTKSK resistance, and all of them exhibited near immunity or high resistance to TTKSK. Among the 131 pyramided lines, 95 showed high resistance to mixed Pst races. Nine lines exhibited not only high resistance to TTKSK and Pst but also better agronomic traits and high-molecular-weight glutenin subunit compositions than Plateau 448.

Impact of increasing temperature anomalies and carbon dioxide emissions on wheat production

Climate change is one of the serious issues humankind is currently facing. It impacts almost all the processes in nature and threatens the existence of species and biodiversity; hence, the whole process of the food cycle. To mitigate the influence of climate change on vital processes in nature, we need to understand the pattern and magnitude of the relationship between climate change and impacted processes in nature. In this article, we explore the impact of climate change on wheat production in terms of short and long-run relationships between world wheat production, carbon dioxide emissions, and surface temperature anomalies. We present new information on the nexus between climate change and wheat production using autoregressive distributed lag (ARDL) models and ARDL bounds test of cointegration. We observe a significant cointegration relationship among world wheat production, carbon dioxide emissions, and surface temperature anomalies series. Lagged short-run impacts of temperature anomalies and carbon dioxide emissions are found significant. The long-run impact of both series on world wheat production is significant with a high correction speed to any instability between wheat production and the proxies of climate change.

Whole-genome sequencing of Puccinia striiformis f. sp. tritici mutant isolates identifies avirulence gene candidates

BackgroundThe stripe rust pathogen, Puccinia striiformis f. sp. tritici (Pst), threats world wheat production. Resistance to Pst is often overcome by pathogen virulence changes, but the mechanisms of variation are not clearly understood. To determine the role of mutation in Pst virulence changes, in previous studies 30 mutant isolates were developed from a least virulent isolate using ethyl methanesulfonate (EMS) mutagenesis and phenotyped for virulence changes. The progenitor isolate was sequenced, assembled and annotated for establishing a high-quality reference genome. In the present study, the 30 mutant isolates were sequenced and compared to the wide-type isolate to determine the genomic variation and identify candidates for avirulence (Avr) genes.ResultsThe sequence reads of the 30 mutant isolates were mapped to the wild-type reference genome to identify genomic changes. After selecting EMS preferred mutations, 264,630 and 118,913 single nucleotide polymorphism (SNP) sites and 89,078 and 72,513 Indels (Insertion/deletion) were detected among the 30 mutant isolates compared to the primary scaffolds and haplotigs of the wild-type isolate, respectively. Deleterious variants including SNPs and Indels occurred in 1866 genes. Genome wide association analysis identified 754 genes associated with avirulence phenotypes. A total of 62 genes were found significantly associated to 16 avirulence genes after selection through six criteria for putative effectors and degree of association, including 48 genes encoding secreted proteins (SPs) and 14 non-SP genes but with high levels of association (P ≤ 0.001) to avirulence phenotypes. Eight of the SP genes were identified as avirulence-associated effectors with high-confidence as they met five or six criteria used to determine effectors.ConclusionsGenome sequence comparison of the mutant isolates with the progenitor isolate unraveled a large number of mutation sites along the genome and identified high-confidence effector genes as candidates for avirulence genes in Pst. Since the avirulence gene candidates were identified from associated SNPs and Indels caused by artificial mutagenesis, these avirulence gene candidates are valuable resources for elucidating the mechanisms of the pathogen pathogenicity, and will be studied to determine their functions in the interactions between the wheat host and the Pst pathogen.

Chemically induced male sterility in common wheat mediated by Aegilops cytoplasm

Several approaches have been proposed, in the past, for the development of hybrid wheat varieties. Nevertheless, common wheat hybrids today account for less than 1% of the world's wheat production. The reason for the limited success of hybrid wheat varieties is the fact that to date, a simple and efficient system for the production of hybrid seed has not been developed. A two-line system using photoperiod-sensitive cytoplasmic male sterility (PCMS) caused by Aegilops crassa Boiss. cytoplasm seems to be very promising way to produce hybrid wheat seed on large scale. Non-desirable side effects of PCMS system are the unreliable sterility of the male sterile lines under different latitudes. Therefore, we tried to connect male sterility system based on Ae. crassa cytoplasm with chemical induction of male sterility. The presented results reveal that the majority of male sterility genes are conserved in the Ae. crassa cytoplasm and that their effects can be promoted by chemical signals, such as synthetic auxins (e.g., 2,4-Dichlorophenoxyacetic acid). Our research work represents the development of a novel male sterility system which is controlled by chemical signals (e.g., synthetic auxins and their pro-herbicide analogues) and mediated by Ae. crassa cytoplasm.

Development of Pasta Products with Nonconventional Ingredients and Their Effect on Selected Quality Characteristics: A Brief Overview.

Pasta is a widely consumed food in all over the world. Coarse semolina obtained from durum wheat and water are the main ingredients of conventional pasta products. The amount of gluten and quality level of durum wheat, are two important factors for the superiority of finished pasta. Market price of durum wheat is higher than the common wheat and it contributes no more than 5% of the world wheat production. Thus, to come across the challenge of emerging pasta consumption, new field of research that is dealing with the incorporation of nonconventional ingredients to the conventional formula of pasta has initiated. The compositions of raw materials which are used for pasta preparation directly affect the physical, chemical, and textural properties of the product. Therefore, incorporation of nonconventional ingredients can lead to a contradictory effect of pasta quality. This review will focus on the various types of nonconventional ingredients that are being incorporated in pasta products and their effect on the quality attributes of different pasta products.

Genetic variations, heritability, heat tolerance indices and correlations studies for traits of bread wheat genotypes under high temperature

PurposeThe purpose of this paper was to study the genetic variability, heritability, heat tolerance indices and phenotypic and genotypic correlation studies for traits of 250 elite International Center for Agricultural Research in the Dry Areas (ICARDA) bread wheat genotypes under high temperature in Wad Medani, Center in Sudan.Design/methodology/approachBread wheat is an important food on a global level and is used in the form of different products. High temperature associated with climate change is considered to be a detrimental stress in the future on world wheat production. A total of 10,250 bread wheat genotypes selected from different advanced yield trials introduction from ICARDA and three checks including were grown in two sowing dates (SODs) (1st and 2nd) 1st SOD heat stress and 2nd SOD non-stress at the Gezira Research Farm, of the Agricultural Research Corporation, Wad Medani, Sudan.FindingsAn alpha lattice design with two replications was used to assess the presence of phenotypic and genotypic variations of different traits, indices for heat stress and heat tolerance for 20 top genotypes and phenotypic and genotypic correlations. Analysis of variance revealed significant differences among genotypes for all the characters. A wide range, 944-4,016 kg/ha in the first SOD and 1,192-5,120 kg/ha in the second SOD, was found in grain yield. The average yield on the first SOD is less than that of the secondnd SOD by 717.7 kg/ha, as the maximum and minimum temperatures were reduced by 3ºC each in the second SOD when compared to the first SOD of the critical stage of crop growth shown.Research limitations/implicationsSimilar wide ranges were found in all morpho-physiological traits studied. High heritability in a broad sense was estimated for days to heading and maturity. Moderate heritability estimates found for grain yield ranged from 44 to 63.6 per cent, biomass ranged from 37.8 to 49.1 per cent and canopy temperature (CT) after heading ranged from 44.2 to 48 per cent for the first and secondnd SODs. The top 20 genotypes are better than the better check in the two sowing dates and seven genotypes (248, 139, 143, 27, 67, 192 and 152) were produced high grain yield under both 1st SOD and 2nd SOD.Practical implicationsThe same genotypes in addition to Imam (check) showed smaller tolerance (TOL) values, indicating that these genotypes had a smaller yield reduction under heat-stressed conditions and that they showed a higher heat stress susceptibility index (SSI). A smaller TOL and a higher SSI are favored. Both phenotypic and genotypic correlations of grain yield were positively and significantly correlated with biomass, harvest index, number of spikes/m2, number of seeds/spike and days to heading and maturity in both SODs and negatively and significantly correlated with canopy temperature before and after heading in both SODs.Originality/valueGenetic variations, heritability, heat tolerance indices and correlation studies for traits of bread wheat genotypes under high temperature

Temperature‐sensitive wheat stem rust resistance gene Sr15 is effective against Puccinia graminis f. sp. tritici race TTKSK

The wheat stem rust fungus, Puccinia graminis f. sp. tritici (Pgt), race TTKSK and related races pose a serious threat to world wheat production. Knowing the effectiveness of wheat stem rust resistance (Sr) genes against Pgt race TTKSK is fundamental in mitigating this threat through resistance breeding. Sr15 was previously identified as being ineffective against Pgt race TTKSK. Here, multirace disease phenotyping data, linkage analyses, allelism testing and haplotype analyses are presented to support the conclusion that Sr15 is effective against Pgt race TTKSK. Resistance to race TTKSK was mapped to Sr15 in a biparental population. Thirty‐two accessions with Sr15 displayed seedling resistance phenotypes against race TTKSK. However, these accessions were susceptible as seedlings at high temperatures (22–25 °C), consistent with previous reports that the interaction between avirulent Pgt isolates and Sr15 is temperature‐sensitive. Markers STS638, wri4 and KASP_IWB30995 were found to predict the presence of Sr15, suggesting the utility of these assays for marker‐assisted selection in breeding programmes. The effectiveness of Sr15 to specific Pgt races and temperatures makes it a less‐desirable TTKSK‐effective gene. Wheat lines assayed as resistant to race TTKSK at the seedling stage may possess Sr15 and breeders should be aware of the limitations of Sr15 for conferring stem rust resistance.

Genetic Characterization of Stem Rust Resistance in a Global Spring Wheat Germplasm Collection

Stem rust, caused by the fungus Puccinia graminis Pers. f. sp. tritici Ericks, is one of the most damaging diseases of wheat (Triticum aestivum L.). The recent emergence of the stem rust Ug99 race group poses a serious threat to world wheat production. Utilization of genetic resistance in cultivar development is the optimal way to control stem rust. Here, we report association mapping of stem rust resistance in a global spring wheat germplasm collection (2152 accessions) genotyped with the wheat iSelect 9K single‐nucleotide polymorphism array. Using a unified mixed model method (or QK method), we identified a total of 47 loci that were significantly associated with various stem rust resistance traits including field disease resistance and seedling resistance against multiple stem rust pathogen races including BCCBC, TRTTF, TTKSK (Ug99), and TTTTF. The 47 loci could be further condensed into 11 quantitative trait locus (QTL) regions according to linkage disequilibrium information among adjacent markers. We postulate that these QTLs represent known stem rust resistance genes including Sr2, Sr6, Sr7a, Sr8a, Sr9h, Sr13, Sr28, and Sr36. We further employed a multilocus mixed model to explore marker‐trait associations and identified two additional QTLs (one potentially represents Sr31) that were significantly associated with stem rust resistance against various races. Combinations of the most significant loci for each trait explained up to 38.6% of the phenotypic variance. Markers identified through this study could be used to track the genes or QTLs. Accessions with high numbers of resistance‐associated alleles may serve as important breeding materials for stem rust resistance.

Molecular Cytogenetic Characterization of two Triticum-Secale-Thinopyrum Trigeneric Hybrids Exhibiting Superior Resistance to Fusarium Head Blight, Leaf Rust, and Stem Rust Race Ug99.

Fusarium head blight (FHB), leaf rust, and stem rust are the most destructive fungal diseases in current world wheat production. The diploid wheatgrass, Thinopyrum elongatum (Host) Dewey (2n = 2x = 14, EE) is an excellent source of disease resistance genes. Two new Triticum–Secale–Thinopyrum trigeneric hybrids were derived from a cross between a hexaploid triticale (X Triticosecale Wittmack, 2n = 6x = 42, AABBRR) and a hexaploid Triticum trititrigia (2n = 6x = 42, AABBEE), were produced and analyzed using genomic in situ hybridization and molecular markers. The results indicated that line RE21 contained 14 A-chromosomes, 14 B-chromosomes, three pairs of R-chromosomes (4R, 6R, and 7R), and four pairs of E-chromosomes (1E, 2E, 3E, and 5E) for a total chromosome number of 2n = 42. Line RE62 contained 14 A-chromosomes, 14 B-chromosomes, six pairs of R-chromosomes, and one pair of translocation chromosomes between chromosome 5R and 5E, for a total chromosome number of 2n = 42. At the seedling and adult growth stages under greenhouse conditions, line RE21 showed high levels of resistance to FHB, leaf rust, and stem rust race Ug99, and line RE62 was highly resistant to leaf rust and stem rust race Ug99. These two lines (RE21 and RE62) display superior disease resistance characteristics and have the potential to be utilized as valuable germplasm sources for future wheat improvement.

Wheat Blast: A New Fungal Inhabitant to Bangladesh Threatening World Wheat Production.

World wheat production is now under threat due to the wheat blast outbreak in Bangladesh in early March 2016. This is a new disease in this area, indicating the higher possibility of this pathogen spreading throughout the Asia, the world’s largest wheat producing area. Occurrence of this disease caused ~3.5% reduction of the total wheat fields in Bangladesh. Its economic effect on the Bangladesh wheat market was little because wheat contributes to 3% of total cereal consumption, among which ~70% have been imported from other countries. However, as a long-term perspective, much greater losses will occur once this disease spreads to other major wheat producing areas of Bangladesh, India, and Pakistan due to the existing favorable condition for the blast pathogen. The wheat blast pathogen belongs to the Magnaporthe oryzae species complex causing blast disease on multiple hosts in the Poaceae family. Phylogenetic analysis revealed that the Bangladesh outbreak strains and the Brazil outbreak strains were the same phylogenetic lineage, suggesting that they might be migrated from Brazil to Bangladesh during the seed import. To protect wheat production of Bangladesh and its neighbors, several measures including rigorous testing of seed health, use of chemicals, crop rotation, reinforcement of quarantine procedures, and increased field monitoring should be implemented. Development of blast resistant wheat varieties should be a long-term solution and combination of different methods with partial resistant lines may suppress this disease for some time.