Tritici Erikss Research Articles

Registration of ‘KS Big Bow’ hard white winter wheat

Abstract‘KS Big Bow’ (Reg. no. CV‐1206, PI 701521), a hard white winter wheat (Triticum aestivum L.) cultivar, was developed by the wheat breeding program at the Agricultural Research Center–Hays, Kansas State University, and released by the Kansas Agricultural Experiment Station in 2022. KS Big Bow was selected from a single cross of KS050223M‐2/KS11HW15 using a modified bulk breeding method. The main objective of this cross is to release a competitive hard white winter wheat cultivar with adaptation to the dryland production in western Kansas. KS Big Bow is an F5‐derived line and was tested in yield trials from 2017 to 2022 in Kansas before its release. It has performed well in dryland yield trials in western Kansas. KS Big Bow has a medium to medium‐early maturity and medium plant height. Its test weight and straw strength are good. KS Big Bow has a good disease‐resistant package including resistance to Wheat streak mosaic virus, moderate resistances to stripe rust (caused by Puccinia striiformis Westend. f. sp. tritici Erikss.) and stem rust (caused by P. graminis Pers f. sp. tritici Eriks. & E. Henn.), and intermediate resistance to Barley yellow dwarf virus. Its milling and baking qualities are about average.

Analysis of resistance to stem rust and identification of <i>Sr</i> genes in introgressive lines of spring bread wheat

Background. Due to the increase in the harmfulness of wheat stem rust (Puccinia graminis f. sp. tritici Erikss. & E. Henn.) in the Volga region, and the likelihood of the spread of the aggressive Ug99 race, an assessment of the genetic diversity of wheat breeding lines and identification of effective Sr genes are of fundamental importance.Materials and methods. Ninety spring bread wheat introgressive lines with stem rust resistance, developed at the Federal Center of Agriculture Research of the South-East Region, were analyzed. Molecular markers were used to identify resistance genes: Sr24/Lr24, Sr25/Lr19, Sr26, Sr28, Sr31/Lr26, Sr32, Sr36, Sr38/Lr37, Sr39 and Sr57/Lr34. The analysis of plants for resistance was carried out according to standard methods; the Stakman scale was applied to determine the type of reaction.Results. The genes Sr31/Lr26, Sr25/Lr19, Sr57/Lr34, Sr38/Lr37 and Sr39/Lr35 were identified in the analyzed breeding lines. Sr25 was found in 51 lines (56,7% of samples), Sr31 in 41 lines (45.6%), Sr57/Lr34 in 5 lines, Sr38 in 10 lines and Sr39 in one line. Combinations of resistance genes were identified: Sr31+Sr25 in 28 lines (31.1%), Sr25+Sr38 in 5 lines, and Sr25+Sr39 in one line. The Sr24/Lr24, Sr26, Sr28, Sr32 and Sr36 genes were not identified.Conclusion. As a result, promising highly resistant introgressive wheat lines with promising combinations of Sr31+Sr25, Sr25+Sr38 and Sr25+Sr39 genes were identified. They can be used in Russian breeding programs for immunity.

Identification of high-temperature resistance to stripe rust and molecular detection of Yr genes in Chinese core collections of common wheat

Stripe rust is a serious wheat disease caused by Puccinia striiformis Westend f. sp. tritici Erikss. High-temperature resistance, which can be induced when the diurnal cycle changes to 15–28 °C or warmer temperatures, has been demonstrated to be non-race specific and durable. The objectives of this study were to evaluate a core collection of 305 Chinese wheat cultivars and landraces for responses to stripe rust in both seedling and adult-plant stages in the greenhouse and the field, determine the distribution of previously reported Yr genes, and select accessions with effective resistance, especially high-temperature resistance. Fifty-eight (19.0%) entries were found to carry all-stage resistance, 71 (23.3%) entries showed adult-plant resistance, 13 (4.3%) entries showed high-temperature all-stage (HTAS) resistance, and 8 (2.6%) entries showed high-temperature adult-plant (HTAP) resistance. Molecular marker detection identified Yr9, Yr10, Yr17, Yr18, Yr26, Yr30, Yr41, Yr78, and Yr80 at different frequencies in the collection, but did not detect Yr5, Yr15, and Yr36. The results in this study would be useful for the rational distribution of cultivars in different regions and breeding for new cultivars with effective and durable resistance.

Haplotype variants of the stripe rust resistance gene Yr28 in Aegilops tauschii.

Stripe rust resistance gene YrAet672 from Aegilops tauschii accession CPI110672 encodes a nucleotide-binding and leucine-rich repeat domain containing protein similar to YrAS2388 and both these members were haplotypes of Yr28. New sources of host resistance are required to counter the continued emergence of new pathotypes of the wheat stripe rust pathogen Puccinia striiformis Westend. f. sp. tritici Erikss. (Pst). Here, we show that CPI110672, an Aegilops tauschii accession from Turkmenistan, carries a single Pst resistance gene, YrAet672, that is effective against multiple Pst pathotypes, including the four predominant Pst lineages present in Australia. The YRAet672 locus was fine mapped to the short arm of chromosome 4D, and a nucleotide-binding and leucine-rich repeat gene was identified at the locus. A transgene encoding the YrAet672 genomic sequence, but lacking a copy of a duplicated sequence present in the 3' UTR, was transformed into wheat cultivar Fielder and Avocet S. This transgene conferred a weak resistance response, suggesting that the duplicated 3' UTR region was essential for function. Subsequent analyses demonstrated that YrAet672 is the same as two other Pst resistance genes described in Ae. tauschii, namely YrAS2388 and Yr28. They were identified as haplotypes encoding identical protein sequences but are polymorphic in non-translated regions of the gene. Suppression of resistance conferred by YrAet672 and Yr28 in synthetic hexaploid wheat lines (AABBDD) involving Langdon (AABB) as the tetraploid parent was associated with a reduction in transcript accumulation.

Using the gene pool of CIMMYT cultivars and lines in spring durum wheat breeding in Western Siberia

Background. Preservation and expansion of the source material genetic diversity and its purposeful use is the basis for the development of adaptable spring durum wheat cultivars for the environments of Western Siberia.Materials and methods. The target research material included the cultivars and promising material of Triticum durum Desf. developed in the Spring Durum Wheat Breeding Laboratory of Omsk Agrarian Scientific Center as well as the gene pool of cultivars and lines obtained under the CIMMYT International Cooperation Program. Field trials, disease resistance assessment and phenological observations were carried out on the experimental fields of the Institute in 2000–2020 according to generally accepted methods. Principal component analysis was carried out using the R version of the 4.0.3 package.Results. The studies have shown that CIMMYT lines differ from local cultivars and lines in disease resistance (brown rust, stem rust, hard smut, and powdery mildew), test weight, pasta-making properties, and lodging resistance, but under the conditions of Western Siberia they are significantly inferior in adaptability to local cultivars and lines and suffer greatly from drought, especially during the grain-filling period. In the genetic control of the studied traits, the additive-dominant system with the inclusion of the complementary recessive epistasis prevails. Local cultivars dominated in most of the studied traits, except the stem length, and the length and diameter of the second internode, where short-stemmed cultivars affected the degree of the traits’ expression in hybrids.Conclusion. The result of such activity was the release of cv. ‘Omsky Korall’, which combines high yield, adaptability to the climate of Western Siberia, and resistance to the local population of Puccinia graminis Pers. f. sp. tritici Erikss. et Henn. and Ug99, with excellent pasta-making properties, as well as the presence of promising lines in all breeding nurseries.

EFFECT OF SALICYLIC ACID AND OXALIC ACID ON THE RESISTANCE TO WHEAT RUST DISEASE (BASIDIOMYCETES, UREDINALES, PUCCINIA)

Wheat rust pathogens belong to genus Puccinia, family Pucciniaceae, order Uredinales and class Basidiomycetes. During epiphytosis, the fungus causes significant damage to crops, disrupts assimilation processes in plants and reduces photosynthesis. Spring soft wheat Arai variety was tested for rust resistance. In this study, we used different concentrations of salicylic acid and oxalic acid. We treated the wheat seeds and seedlings with different concentrated acids. In the context of the artificial epidemic, during the rooting, dulling and germination stages of wheat development, we were infected with spores of yellow rust (Puccinia striiformis f.sp. tritici), brown rust (Ruccinia tritici Erikss) and stem rust (Puccinia graminis Pers. F. Sp. Tritici). We tested the effect of different concentrations of salicylic acid and oxalic acid on wheat rust disease.. The results of the study showed that the seeds were found to be moderately resistant to yellow rust of wheat treated with concentrated acid 0.25 mM SA + 0.1 mM OA (1) and 0.25 mM SA + 0.2 mM OA (3). 0.5 mM SA + 0.2 mM OA (2) was immunocompromised to brown rust when treated with concentrated acid spray. In organic agriculture, the chemical control of deafness in wheat leads to environmental pollution, in addition is not economically viable and a realistic way to combat it. Therefore, we need to look for effective ways for disease control. The data obtained in the study allow to fight against yellow rust and brown rust of wheat.

DIAGNOSTICS OF RUSTS AND SPOTTS OF WHEAT USING COMPUTER VISION METHODS

Purpose. To investigate the possibility of diagnosing yellow and brown rust (Puccinia striiformis f. sp. tritici West. Puccinia triticina f. sp. tritici Erikss), yellow spot (Pyrenophora tritici-repentis (Died.) Drechsler) on wheat leaves from images using convolutional neural networks, to compare the most successful and compact neural network architectures.
 Materials and methods. The material for the research was the images of samples of wheat leaves affected by rust and spots, obtained in the conditions of infectious nurseries of the All-Russian Research Institute of Biological Plant Protection. The total sample size included 5169 images, including brown rust - 227, yellow rust – 1283, yellow spot – 3659. Research methods: data preprocessing methods, training methods for convolutional neural networks.
 Results. A comparison was made of the four most successful and compact neural network architectures GoogleNet, ResNet-18, SqueezeNet-1.0 and DenseNet-121. On test data – 518 images, all of the above models demonstrated high prediction quality. The best result was shown by DenseNet-121, providing a classification accuracy of over 99 %, with two false positives.
 Conclusion. The possibility of diagnosing wheat fungal diseases from images using modern methods of computer vision was analyzed. It is shown that under controlled conditions, with a competent organization of the process of collecting and marking data, the problem is successfully solved, and the listed models are the reserve that will automate the stage of phytosanitary monitoring diagnostics.

First Report of Races TKTTP and TKKTP of Puccinia graminis f. sp. tritici with Virulence to Wheat Stem Rust Resistance Gene Sr24 in Turkey and Tunisia

Severe wheat stem rust caused by Puccinia graminis Pers.:Pers. f. sp. tritici Erikss. (Pgt) can result in complete crop failure. In recent years, the increasing frequency and the early onset of stem rust in Central West Asia and North Africa (CWANA) has become a big concern. The Sr24 resistance gene, one of the most effective stem rust resistance genes effective against most P. graminis f. sp. tritici races worldwide, has been widely deployed. Until the recent establishment of virulence to Sr24 within the Ug99 lineage of the pathogen in Africa (Hei et al. 2020; Jin et al. 2008; Patpour et al. 2015), Iraq (Nazari et al., 2021), occasional detections of races virulent to Sr24 were reported in South Africa (Le Roux and Rijkenberg 1987), India (Bhardwaj et al. 1990), Germany (Olivera Firpo et al. 2017), Georgia (Olivera, et al. 2019), and Western Siberia (Skolotneva et al., 2020). During the rust surveys conducted in Sinops, Samsun, and Kastomonu in the Black Sea region in northern Turkey in 2018, 19 isolates were collected. Single pustule (SP) isolates were developed and used in race analysis in the Biosafety Rust Laboratory, Regional Cereal Rust Research Center (RCRRC), Izmir, Turkey. Sample recovery, experimental procedures for pre-inoculation, inoculation, incubation, and race typing were conducted as previously described (Nazari et al. 2021). Among the tested SP isolates, two isolates showed a high infection type (IT) of 33+ on the Sr24 tester line (Little Club/Agent) and a low infection type of 11+ for the source of Sr31 (Benno/6*LMPG-6). Eight SP isolates were further developed from the high IT 33+ pustules collected from the Sr24 tester line. After spore multiplications, they were used in inoculation of the 20 North American stem rust single-gene lines used to differentiate races of P. graminis f. sp. tritici, plus Trident (Sr38+), Siouxland (Sr24+Sr31), and Sisson (Sr31+Sr36). Five SP-derived isolates with IT 33+ on the Sr24 single-gene line collected from Samsun (Alacam - Etyemez; Location: N 41.61889 E 35.55722) and Sinop (Merkez-Sanlıoglu; Location: N 41.85556 E 35.04889) were identified as race TKKTP and the remaining three SP isolates as race TKTTP. In 2020, we detected two isolates of TKKTP among the stem rust samples from Tunisia submitted to RCRRC. These two isolates were collected from bread wheat cultivars Heydna and Tahmet at a trial site near Bou Salem in Western Tunisia (Location: N 36.5351 E 8.95486). Based on the negative results of the Stage 1 test using a suite of four real-time polymerase chain reaction assays diagnostic for the Ug99 race group developed by Szabo (2012), these two races should not belong to the Ug99 race group when compared to the reference Ug99 race TTKTT from Kenya. These races were virulent to Sr5, Sr21, Sr9e, Sr7b, Sr6, Sr8a, Sr9g, Sr9b, Sr30, Sr17, Sr9a, Sr9d, Sr10, SrTmp, Sr24, Sr38, and SrMcN. In addition to these genes, race TKTTP was virulent to Sr36. Both races were avirulent to Sr11 and Sr31. To our knowledge, this is the first report of P. graminis f. sp. tritici races with the Sr24 virulence in Turkey and Tunisia. The results reflect an increasing trend of virulence to Sr24 in the pathogen populations, and raise a great concern given the deployment of the Sr24 resistance gene in widely grown wheat cultivars worldwide.

Mapping quantitative trait loci associated with stripe rust resistance from the Canadian wheat cultivar ‘AAC Innova’

Stripe rust, caused by Puccinia striiformis Westend. f.sp. tritici Erikss. (Pst), is one of the most devastating diseases of wheat (Triticum aestivum L.) globally. Exploring and utilizing new sources of resistance is essential for breeding resistant wheat cultivars. Thus, a doubled haploid population (n = 291) derived from the cross ‘AAC Innova’/‘AAC Proclaim’ was evaluated to dissect the genetics of resistance in the cultivar ‘AAC Innova’. This population was evaluated for stripe rust severity in disease nurseries at Creston, British Columbia (in 2016 and 2020), and Lethbridge, Alberta (in 2016, 2017 and 2020), and genotyped using the wheat 90 K SNP assay. A high-density genetic map was constructed which consisted of 7112 SNP markers with an average marker interval of 2.3 cM. Quantitative trait loci (QTL) mapping identified one major (QYr.lrdc-2A) and 10 minor effect (QYr.lrdc-2B.1, QYr.lrdc-2B.2, QYr.lrdc-2B.3, QYr.lrdc-2B.4, QYr.lrdc-2D, QYr.lrdc-3B, QYr.lrdc-5A, QYr.lrdc-5B, QYr.lrdc-5D and QYr.lrdc-7D) loci. The QTL QYr.lrdc-2A was consistently effective against Pst races across all environments and explained up to 33.0% of the phenotypic variation. Other QTLs were either less consistent or environment specific. ‘AAC Innova’ contributed stripe rust resistance alleles for most of the QTLs except for QYr.lrdc-2D, QYr.lrdc-5A and QYr.lrdc-7D. The QTLs identified in this study should be valuable for diversifying the sources of genetic resistance against current and new virulent races of Pst. In particular, the ‘AAC Innova’-derived QTL QYr.lrdc-2A could be a valuable source of resistance to incorporate into commercial cultivars and combine with other genes using the associated SNP markers identified in this study.

Registration of the Coda/Brundage wheat recombinant inbred line mapping population

AbstractA mapping population (Reg. no. MP‐15, NSL 540708 MAP) composed of a cross between the soft white common winter wheat (Triticum aestivum L. subsp. aestivum) ‘Brundage’ (PI 599193) and the soft white club winter wheat (T. aestivum L. subsp. compactum) ‘Coda’ (PI 594372) was developed to maximize diversity within the soft white market class. The population comprises 268 F6:7 lines developed through single seed descent. The genetic linkage map consists of 2,144 DNA markers and is assigned to 32 linkage groups covering all chromosomes except 1D. This population was initially developed to determine additional markers linked to the Pch1 gene in wheat. It has further been used to identify quantitative trait loci (QTL) associated with resistance to other diseases such as Cephalosporium stripe (caused by Cephalosporium gramineum) and stripe rust (caused by Puccinia striiformis Westend. f. sp. tritici Erikss). The mapping population has also been used for identification of DNA markers associated with freezing tolerance, end‐use quality, and the compactum locus. From the differences in traits between the parental lines, the Coda/Brundage population provides the opportunity for further inquiry into the genes behind the identified QTL. The parents have only been phenotypically screened for a limited number of traits, and further screening may identify more polymorphic traits which the population can be used to map. It can also serve as a validation population for marker‐trait associations identified in other populations or other genetic studies such as recombination frequency.

Novel stripe rust all-stage resistance loci identified in a worldwide collection of durum wheat using genome-wide association mapping.

Durumwheat [Triticum turgidum L. ssp. durum (Desf.)] production is constrained by fungal diseases including stripe rust caused by Puccinia striiformis Westend. f. sp. tritici Erikss. (Pst). Continuous mining of germplasm for the discovery and deployment of stripe rust resistance (Yr) genes is needed to counter the impact of this disease. In this study, we evaluated a worldwide collection of 432 durum wheat accessions to seven U.S. Pst races that carry diverse virulence and avirulence combinations on wheat Yr genes. We found that 47-82% of the durum wheat accessions were susceptible to each of the tested Pst races. A total of 32 accessions were resistant to all seven races. Genome-wide association studies (GWAS) using over 97,000 single-nucleotide polymorphism markers generated from genotyping-by-sequencingof 364 accessions identified 56 quantitative trait loci (QTL) associated with all-stage stripe rust resistance located on all 14 durum wheat chromosomes. Six of these QTL were associated with resistance to 2-4 Pst races, and none were associated with resistance to all seven races. The remaining 50 QTL were race specific. Eighteen of the 56 identified QTL had relatively large effects against at least one of the races. A map-based comparison of the discovered QTL in this study with previously published Yr genes and QTL showed that 29 were previously identified, whereas the remaining 27 QTL appeared to be novel. This study reports effective sources of stripe rust resistance to contemporary races in the United States and shows that this durum wheat collection is abundant in novel resistance loci that can be transferred into adapted durum cultivars.

Assessment of Resistance to Cereal Cyst Nematode, Stripe Rust, and Powdery Mildew in Wheat-Thinopyrum intermedium Derivatives and Their Chromosome Composition.

Wide hybridization between wheat and wild relatives such as Thinopyrum intermedium is important for broadening genetic diversity and improving disease resistance in wheat. We developed 30 wheat-Th. intermedium derivatives. Here, we report assessments of their resistance to different pathogens including cereal cyst nematode (CCN; Heterodera spp.), Puccinia striiformis f. tritici Erikss. causing stripe rust, and Blumeria graminis f. tritici (DC.) Speer inciting powdery mildew. Under natural field infection, all the wheat-Th. intermedium lines were resistant to at least one of the pathogens, and four lines were resistant to multiple pathogens. Twenty-nine of 30 tested lines exhibited resistance to H. avenae, a dominant CCN species in wheat fields. Twenty-four lines were resistant to H. filipjevi, an emerging threat to wheat production. Tests of phenotypic responses in the naturally infected field nurseries identified six stripe rust-resistant lines and 13 powdery mildew-resistant lines. Mitotic observation demonstrated that these newly developed wheat-Th. intermedium derivatives included not only octoploid but also chromosome addition, substitution, and translocation lines. Chromosome compositions of the four lines resistant to multiple pathogens were analyzed by genomic in situ hybridization and fluorescence in situ hybridization. The octoploid lines Zhong 10-68 and Zhong 10-117 carried both intact Th. intermedium chromosomes and translocated chromosomes. Line Zhong 10-149 had 42 wheat chromosomes and two wheat ditelosomes plus a pair of T3BS·J translocated chromosomes. Line Zhong 10-160 carried 41 wheat chromosomes plus one pair of the J genome chromosomes of Th. intermedium. The multiple disease-resistant wheat-Th. intermedium derivatives, especially lines with chromosome counts close to that of common wheat, provide valuable materials for wheat resistance breeding programs.

Characteristics of the virulence of the wheat stem rust pathogen in the conditions of the Saratov region

Stem rust (pathogen - biotrophic fungus Puccinia graminis f. sp. tritici Erikss. & Henning) – a particularly deleterious disease of bread wheat. In this article the results of the analysis of the structure of samples of Saratov populations of wheat stem rust pathogen by signs of virulence during 2016-2020 were presented. A total of 60 pathogen isolates were characterized for virulence. In general, Saratov P. graminis populations were characterized as highly virulent during the study period. The significant variation in the virulence frequencies of P. graminis was observed in lines with the genes Sr9b, Sr9g, Sr12, Sr21, Sr25, Sr27, Sr30, Sr32, Sr33, Sr7a+12, Sr17+13. The other Sr lines used in the analysis, the virulence rates remained consistently high in all the years of research. Genes and combinations of genes: SrSatu, Sr24, Sr25+9g, Sr25+31, Sr25+38 were shown to be effective to P. graminis populations in 2016-2020.

Effectiveness of Growing Wheat-Variety Blends in Reducing Damage Caused by Stem-Rust (Puccinia graminis pers.f.sp. tritici Erikss. et Henn., the Causal Agent)

Effectiveness of Growing Wheat-Variety Blends in Reducing Damage Caused by Stem-Rust (Puccinia graminis pers.f.sp. tritici Erikss. et Henn., the Causal Agent)

Breeding With Major and Minor Genes: Genomic Selection for Quantitative Disease Resistance.

Disease resistance in plants is mostly quantitative, with both major and minor genes controlling resistance. This research aimed to optimize genomic selection (GS) models for use in breeding programs that are needed to select both major and minor genes for resistance. In this study, stripe rust (Puccinia striiformis Westend. f. sp. tritici Erikss.) of wheat (Triticum aestivum L.) was used as a model for quantitative disease resistance. The quantitative nature of stripe rust is usually phenotyped with two disease traits, infection type (IT) and disease severity (SEV). We compared two types of training populations composed of 2,630 breeding lines (BLs) phenotyped in single-plot trials from 4 years (2016–2020) and 475 diversity panel (DP) lines from 4 years (2013–2016), both across two locations. We also compared the accuracy of models using four different major gene markers and genome-wide association study (GWAS) markers as fixed effects. The prediction models used 31,975 markers that are replicated 50 times using a 5-fold cross-validation. We then compared GS models using a marker-assisted selection (MAS) to compare the prediction accuracy of the markers alone and in combination. GS models had higher accuracies than MAS and reached an accuracy of 0.72 for disease SEV. The major gene and GWAS markers had only a small to nil increase in the prediction accuracy more than the base GS model, with the highest accuracy increase of 0.03 for the major markers and 0.06 for the GWAS markers. There was a statistical increase in the accuracy using the disease SEV trait, BLs, population type, and combining years. There was also a statistical increase in the accuracy using the major markers in the validation sets as the mean accuracy decreased. The inclusion of fixed effects in low prediction scenarios increased the accuracy up to 0.06 for GS models using significant GWAS markers. Our results indicate that GS can accurately predict quantitative disease resistance in the presence of major and minor genes.

Identification of eight Berberis species from the Yunnan-Guizhou plateau as aecial hosts for Puccinia striiformis f. sp. tritici, the wheat stripe rust pathogen

Puccinia striiformis Westend. f. sp. tritici Erikss. (Pst) infects wheat and causes stripe rust. The rust is heteroecious with wheat as the primary uredinial and telial host and barberry (Berberis spp.) as the alternate pycnial and aecial host. More than 40 Berberis species have been identified as alternate hosts for Pst, and most of these are Chinese Berberis species. However, little is known about Berberis species or their geographic distributions in the Yunnan-Guizhou plateau in southwestern China. The Yunnan-Guizhou plateau is considered to be an important and relatively independent region for the evolution of the wheat stripe rust pathogen in China because the entire disease cycle can be completed within the region. In this study, we conducted a survey of barberry plants in the Yunnan-Guizhou plateau and identified the eight Pst-susceptible Berberis species under controlled conditions, including B. julianae, B. tsienii, B. veitchii, B. wilsonae, B. wilsonae var. guhtzunica, B. franchetiana, B. lepidifolia and B. pruinosa. These species are reported here for the first time to serve as alternate hosts for the wheat stripe rust pathogen under controlled conditions.

‘CHEVIGNON’: NUEVA VARIEDAD DE TRIGO DE INVIERNO PARA EL SUR DE CHILE

‘Chevignon’ is a winter wheat variety developed by ASUR Plant Breeding of France and introduced to Chile by the National Wheat Breeding Program at INIA Carillanca. The variety has medium plant height, intermediate cycle, with resistance to yellow rust (Puccinia striiformis West. f. sp. tritici Erikss), and powdery mildew (Blumeria graminis D.C. f. sp. tritici Marchal), moderate resistance to leaf rust (Puccinia triticina f. sp. tritici Erikss y Henn) and tolerance to septoria leaf blotch (Mycosphaerella graminicola (Fuckel) Sand). It is a high yielding winter wheat variety with good quality characteristics for direct baking. It has a prostrate growth habit at seedling stage, with high tillering production. Its leaves are pale green, with a semi-drooping flag leaf. The spike is white, semi-erect, and parallel in shape, compact and without awns. The grain is round, medium-sized, and pale red, with occasional variations in endosperm pigmentation. The adult plant height varies between 105 cm and 110 cm, with an average of 105 cm, and with moderate resistance to lodging. Heading growth stage occurred 5 days later than cultivar Maxwell and 8 to 10 days earlier than ‘Bicentenario INIA’ and ‘Kiron INIA’

Genome-wide mapping and allelic fingerprinting provide insights into the genetics of resistance to wheat stripe rust in India, Kenya and Mexico

Stripe or yellow rust (YR) caused by Puccinia striiformis Westend. f. sp. tritici Erikss. is a persistent biotic-stress threatening global wheat production. To broaden our understanding of the shared genetic basis of YR resistance across multi-site and multi-year evaluations, we performed a large genome-wide association study using 43,706 YR observations on 23,346 wheat lines from the International Maize and Wheat Improvement Center evaluated between 2013 and 2019 at sites in India, Kenya and Mexico, against predominant races prevalent in the countries.We identified 114 repeatable markers tagging 20 quantitative trait loci (QTL) associated with YR on ten chromosomes including 1D, 2A, 2B, 2D, 3A, 4A, 4D, 5A, 5B and 6B, among which four QTL, QYr.cim-2DL.2, QYr.cim-2AS.1, QYr.cim-2BS.2 and QYr.cim-2BS.3 were significant in more than ten datasets.Furthermore, we report YR-associated allelic fingerprints for the largest panel of wheat breeding lines (52,067 lines) till date, creating substantial opportunities for YR favorable allele enrichment using molecular markers. Overall, the markers and fingerprints reported in this study provide excellent insights into the genetic architecture of YR resistance in different geographical regions, time-periods and wheat germplasm and are a huge resource to the global wheat breeding community for accelerating YR resistance breeding efforts.

Resistance to wheat rusts identified in wheat/Amblyopyrum muticum chromosome introgressions.

Wheat (Triticum aestivum L.) rusts are a worldwide production problem. Plant breeders have used genetic resistance to combat these fungi. However, single‐gene resistance is rapidly overcome as a result of frequent occurrence of new virulent fungal strains. Thus, a supply of new resistance sources is continually needed, and new resistance sources are limited within hexaploid wheat genetic stocks. Wild relatives are able to be a resource for new resistance genes but are hindered because of chromosome incapability with domesticated wheats. Twenty‐eight double‐haploid hexaploid wheat/Amblyopyrum muticum (Boiss.) Eig introgression lines, with introgressions covering the majority of the T genome, were evaluated for resistance to Puccinia triticina Erikss., P. graminis Pers.:Pers. f.sp. tritici Erikss. & E. Henning, and P. striiformis Westend. f.sp. tritici Erikss.. At the seedling level, four lines were resistant to races of P. triticina, six lines were resistant to P. graminis, and 15 lines were resistant to P. striiformis. At the adult stage, 16 lines were resistant to P. triticina. Line 355 had resistance to all three rusts and line 161 had resistance to all tested races of P. triticina. Some of these lines will require further work to reduce the size of the introgressed segment; however, lines 92 and 355 have very small fragments and can be used directly as new resistance donors.

Role of Fungicide Applications on the Integrated Management of Wheat Stripe Rust.

First described in Europe in 1777, stripe rust (SR) caused by Puccinia striiformis Westend. f. sp. tritici Erikss (Pst) is one of the most important and destructive diseases of wheat worldwide. Until 2000, SR was mainly endemic to cooler regions, but since then, new aggressive strains have emerged, spread intercontinentally, and caused severe epidemics in warmer regions across the world. This has put SR as a disease that poses a threat to the world food security. At present, the preferred strategy for control of SR is the access to wheat cultivars with adequate levels of SR resistance. However, wheat breeding programs are not sufficiently advanced to cope with the recently emerged Pst strains. Under this scenario, foliar fungicide applications have become an important component of SR management, but information on the effects of fungicide applications on SR control and wheat cultivar yield response is scarce. This review seeks to provide an overview of the impact and role of fungicides on SR management. With focus on wheat management in the major wheat-growing regions of the world, the review addresses: (a) the efficacy of different fungicide active ingredients, optimal fungicide timing and number of applications in controlling SR, and (b) the impact of fungicide on wheat grain yield response. Inclusion of fungicides in an integrated crop management approach is discussed.