Institute of Evolution and the Department of Evolutionary and Environmental Biology, University of Haifa, Israel
Dina Raats, Lin Huang, Valeria Bocharova, Jorge Dubcovsky, Abraham Korol, Tzion Fahima
Wild emmer wheat (Triticum dicoccoides, (DIC)) is an important source of resistance to stripe rust due to presence of Puccinia striiformis in its natural habitats with high humidity and relatively low temperatures that are favorable for stripe rust development. Previously, we showed that DIC accessions from northern Israel were highly resistant to stripe rust. According to the rust responses of three DIC accessions (G25, H52, G303) and mapping of the resistance to relatively close, but different, genetic positions on chromosome 1BS, three different resistance genes were assumed to be present. However, the development of additional critical recombinants and new higher resolution genetic maps for these three genes in subsequent work led us to place YrH52 and YrG303 in the same genetic interval as Yr15, suggesting that the three putative genes are allelic or identical. The recent cloning of Yr15 allowed us to test this hypothesis using an EMS mutagenesis approach. We sequenced the Yr15 locus in five yrH52 and three yrG303 susceptible mutants and identified missense point mutations associated with the susceptible phenotype in each one. Thus, YrH52 and YrG303 may not be new genes. Further work is under way to determine if these genes are allelic or identical.
Agriculture & Agri-Food Canada
Wheat cultivar McNair 701 carries resistance gene SrMcN and is used as a differential line to identify Pgt races using the international letter code nomenclature. The inheritance and location of the resistance gene has not been characterized. We developed a doubled haploid (DH) population from cross LMPG/McNair 701 to study the genetics and chromosomal location of SrMcN. A DH population inoculated with race QCCJB segregated 100 resistant : 94 susceptible, a 1:1 ratio (?2=0.186, P=0.666, NS) indicative of segregation at a single locus. This gene was mapped to chromosome 2DL using the Infinium 90k platform. The map position of SrMcN was similar to that of Sr54, one of two genes previously found in Norin 40. Comparison of stem rust seedling reactions using 12 diverse Pgt races indicated that McNair 701 and an Sr54 line derived from Norin 40 had an identical pattern of responses and similar low infection types (IT=12-) to races LCBNB and QCCJB. Based on the chromosomal location on 2DL and identical seedling responses to Sr54, it is likely that the resistance gene in McNair 701 formerly known as SrMcN is Sr54. This finding will be confirmed by a test of allelism.
James Winans, Julian Garcia, Kellie Damann, Gary Bergstrom
In addition to causing Fusarium head blight of wheat and other cereals, Fusarium graminearum is associated with dozens of wild or weedy grass species. Their role in the disease cycle and evolution of the pathogen has not been established despite their widespread distribution. A three-year survey of wild grasses in New York (USA) found that inflorescences and overwintered stems were frequently colonized by F. graminearum. Through a series of controlled laboratory experiments, wheat and five common grass species were compared for their potential to support inoculum production. Artificially infested stem tissue from several grasses both retained F. graminearum at higher rates through a single winter and supported greater ascospore production per dry gram than wheat. Susceptibility of these species to root and crown rot was measured with a modified seed germination assay and a diverse panel of F. graminearum isolates. Differences were seen between host species, and some grasses were resistant to infection. Our results indicate that wild grass species may support significant F. graminearum inoculum production while differing in their suitability for root and crown colonization. Studying interactions between F. graminearum and alternative host plants can improve our understanding of evolution in a broad host range pathogen and our ability to predict the risk of crop epidemics. We are currently evaluating isolates collected from wild grasses for mycotoxin production and aggressiveness on wheat.
Wheat Research Institute, Faisalabad, Pakistan
Ghulam Mahboob Subhani, Javed Ahmad, Abid Mahmood
Global warming affects the environmental parameters of agro-based countries like temperature increase, melting of glaciers, floods, erratic rains, low temperature, frost and high temperature. As a result agriculture is becoming more vulnerable to global environmental shifts. In case of wheat, erratic or low rains badly affect the wheat crop of rainfed areas of the country along with high temperature at seedling or juvenile stage. Similarly, frost affects the early sown wheat crop in irrigated areas of Punjab. Lesser availability of irrigation water from water reservoirs also reduces the wheat crop productivity. Sudden increase in temperature (>30?C) during the month of March adversely affect the grain filling. High temperature during grain filling stage interferes with the photosynthetic activities of the plant due to enhanced maturity, grain become shriveled and results in low grain yield. The threat of these environmental changes can only be overcome through breeding with specific objectives which is cost effective once obtained.
Hence development of wheat varieties for frost, drought and heat tolerance is the only feasible solution to combat these stresses which is being used at Wheat Program of Ayub Agricultural Research Institute, Faisalabad, Pakistan. New emphasis is also being given to develop frost resistant wheat varieties due to changing scenario of last few years. The institute is actively involved for the development of heat, drought and frost tolerant wheat varieties. During working for tolerance against any of these stresses plant types to be breed are physiologically and morphologically modeled in such a way that they should be capable of tolerating respective stress. In addition to breeding work an extensive research is also being done at Wheat Research Institute, AARI., Faisalabad to investigate best agronomic strategies to make wheat crop best adapted to environmental stress conditions.
National Institute of Agricultural Research
Nsarellah Nasserlhaq, Wuletaw Tadesse, Ahmed Birouk
In the context of climate change, drought is one of the most important and complex abiotic stresses affecting crop production worldwide. The adoption of an appropriate technological package, principally drought tolerant varieties, may overcome these challenges to meet global food security needs for the rapidly growing human population, particularly in developing countries. Therefore, this research was carried out to identify efficient phenotypic and genetic selection criteria to identify drought tolerant wheat varieties. In this perspective, 200 diverse elite bread wheat lines from ICARDA and CIMMYT were evaluated under four Moroccan environments during the 2015 and 2016 seasons for yield and 15 agro-physiological traits. The same set of genotypes was genotyped using 15k SNPs. Significant environment and genotype environment interaction effects were observed for yield. Average yield reached 3.18t/ha and ranged from 2.45 to 4.27t/ha. The secondary traits were mostly dominated by the environment effect (p<0.001). Based on correlation and regression analysis between grain yield and phenotypic data, the biomass, grain number per m<sup>2</sup> and to a lesser extent fertile spikes number and thousand kernel weights (depending of drought scenarios) can be more reliable traits than yield for the identification of drought tolerant genotypes. Moreover, the ground cover and canopy temperature depression can be used as supplementary criteria for more accurate selection. Slow selection on the basis of phenotypic traits may be accelerated and improved by using molecular markers. The genetic analysis highlighted significant SNPs and identified new QTLs linked to yield and the most efficient phenotypic traits under drought conditions. These findings could be useful for breeding drought-resistant wheat cultivars using marker-assisted selection to accumulate these favorable alleles of SNPs associated with yield-related traits to increase grain yield.
Agriculture Botany Division, Nepal Agricultural Research Council
Baidya Nath,Mahto, Sarala, Sharma, Madan Raj, Bhatta, Mahesh, Subedi, Deepak, Pandey, Nutan Raj, Gautam, Suraj, Baidya, Roshan, Basnet, Rudra, Bhattarai, Ajaya, Karkee, Suk Bahadur, Gurung, Prem Bahadur, Magar, Sunita, Adhikari, Bhagarathi, Shahi, Basistha, Acharya
A total of 41 bread wheat (Triticum aestivum L.) varieties have been released so far in Nepal since 1960. Farmers have been gradually adopting newly released varieties due to disease and lodging resistance, better yield performance and good taste. In Nepal, wheat area coverage, production and productivity have been increased by almost seven, sixteen and two folds, respectively in the last 56 years. Performance of varieties varies from one region to another. Yellow rust is the major problems in hills while leaf rust is the primary issue on the plains. Stem rust is sporadic in localized areas of Nepal. Wheat research program in Nepal has released 9 wheat varieties resistant to Ug99 namely Vijaya, Tilottama, Banganga, Gaura, Dhaulagiri, Danphe, Sworgadwari, Munal and Chyakhura. Vijay, Tilottama and Banganga are also resistant to leaf rust while, Dhaulagiri, Danphe, Sworgadwari, Munal and Chyakhura are resistant to yellow rust. Since the release of Vijay, the first Ug99 resistant variety in Nepal during 2010, source seed production of rust resistant varieties has been increasing significantly each year with present coverage under these varieties being around 40%. WK 1204 has been occupied 35% area in hills of Nepal. Seed production and distribution of such high yielding disease resistant varieties through public-private partnership is leading to quality seed supply for varietal diversity and better food security in the country.
The University of Sydney
Davinder Singh, Peter Dracatos
Following the introduction of wheat stripe rust into Australia in 1979, an uncharacterized resistance (YrA) was identified in both Australian and International spring wheats. Genetic analyses of YrA indicated it was a pair of complementary genes, which were mapped to chromosomes 3DL and 5BL and designated Yr73 and Yr74, respectively. While selection Avocet 'R' carries both genes, selection Avocet 'S' carries Yr73 only. P. triticina pathotype (pt.) 104-1,2,3,(6),(7),11 +Lr37 ("104-VPM"), first detected in Australia in 2002, most likely arose via mutation from pt. 104-1,2,3,(6),(7),11 ("104"), with added virulence for Lr37. Interestingly, while both pathotypes are avirulent on Lr13, 104-VPM shows a much lower Infection Type (IT, ";1") than pt. 104 ("X++3") on several genotypes carrying Lr13 (e.g.Avocet 'R', Avocet 'S'). Other Lr13 genotypes (e.g. cv. Hereward) respond similarly to both pts ("X++3"). Genetic analyses of 4 doubled haploid (DH) populations based on intercrosses between Avocet 'R' and genotypes lacking Lr13 segregated in a 1:7 ratio to pt. 104-VPM (";1" : all other ITs). Two populations fixed for Lr13 (viz. Hereward/ Avocet 'R' and Estica/Avocet 'R') segregated 1:3 to pt. 104-VPM (";1" : all other ITs). This segregation pattern fitted a model where two complementary genes interact with Lr13 to generate the low (IT ";1") IT. Mapping of a Teal/Avocet 'R' DH population using 92 lines and 9,035 DArT-Seq markers identified three QTLs: chromosome 2BS (Lr13); chromosome 3DL (co-located with Yr73); chromosome 1DS. These results suggest that Yr73 acts in a complementary manner with a gene on chromosome 1DS to confer leaf rust resistance (IT "X"), and that these complementary genes are additive with Lr13. It appears that Yr73 is a modifier of two independent genes in wheat, one conferring resistance to stripe rust (Yr74 on chromosome 5BL), and one conferring resistance to leaf rust (LrAv on chromosome 1DS).
Institute of Plant Biology and Biotechnology
Makpal Atishova, Aygul Madenova, Kanat Galymbek, Jenis Keyshilov, Hafiz Muminjanov, Alexey Morgounov
Wheat rust diseases are a major cause of yield losses of this crop. Yellow (Puccinia striiformis f. sp. tritici) rust is of the most widespread and dangerous disease of wheat and is the major factor that adversely affects wheat yield and quality. The use of genetic host resistance is the most effective, economical and environmentally safe method of controlling stripe rust that allows elimination of fungicides and minimize crop losses from this disease. Due to the threat of the development of epiphytoties of rust disease it is necessary to identify new donors of resistance to yellow rust and to develop resistant wheat breeding material. In the present study, attention was drawn to the effective yellow rust resistance genes Yr5, Yr10 and Yr15, which were identified in the process of molecular screening of wheat germplasm. Genetic analysis using S23M41 molecular marker linked to Yr5 revealed the presence of this gene in 17 out of 136 promising lines. Thirteen genotypes screened with Xbarc8 generated the DNA fragment associated with Yr15. Three advanced lines with Yr10 were identified using the SCAR marker. Three lines carrying two Yr genes (Yr5 and Yr15) were detected. Combination of Yr5 and Yr10 were found in 15 wheat lines. We identified a number of wheat genotypes highly resistant to stripe rust, which could be further evaluated to release new resistant varieties or to be used in the breeding program.
Genetic Resources Institute, Azerbaijan
N. Aminov, A. Jahangirov, H. Hamidov, Aigul Abugalieva, Vladmir Shamanin, Alexey Morgunov
Hexaploid synthetics have become widely used in bread wheat improvement in recent years, enabling the introduction of specific traits as well as enhancing genetic diversity and development of valuable germplasm. This study demonstrated the difference between two groups of primary synthetics in terms of development rate, plant height, rust reactions, and productivity components. During 2015 and 2016, three groups of synthetics were studied in Azerbaijan (3 sites): Baku (0 masl) under irrigated conditions, Gobustan (850 masl) under dry rainfed conditions and Ujar (20 masl) under irrigated conditions with high salinity. Germplasm was also evaluated for diseases and agronomic traits in Omsk (Russia) in 2016.
All primary synthetics were resistant to leaf rust, several to stem rust, and few to stripe rust. Stripe rust occurred in all years at all sites, proving its importance as major wheat pathogen. Its severity reached intermediate levels in Baku in 2016 (33.7%) and in Gobustan in 2015 (26.8%), and epidemic level in Gobustan in 2016 (72.7%). Gobustan also experienced high levels of stem rust in 2016. These two diseases substantially reduced grain productivity in Gobustan in 2016, especially 1000 kernel weight (30.2 g) and grain weight per spike (1.17 g). . Superior genotypes from all three groups were identified that combine high expression of spike productivity traits and stress tolerance index. Five superior synthetics were selected from each of the three groups, based on grain weight per spike. Only four of these demonstrated resistance to stripe rust (entries 13, 15, 31, and 32). Japanese synthetics (group 3) were susceptible to stripe rust but all demonstrated resistance to stem rust. Synthetics from groups 1 and 3 were all resistant to leaf rust when tested under severe disease pressure in Omsk in 2016.
Ethiopian Institute of Agricultural Research (EIAR)
Stripe rust caused by Puccinia striiformis f.sp.tritici, is one of the major diseases of wheat in the world. Experiments were carried out at two sites in Ethiopia (Kulumsa and Meraro) during the 2015 cropping season to evaluate the response of 198 elite bread wheat genotypes and two checks to the prevailing races of stripe rust at adult plant and seedling stage. The genetic profile of these genotypes was assessed using 13006 SNP markers and an association mapping was explored to determine marker?trait association. About 72.5% and 42.5% of the lines exhibited resistance at Kulumsa and Meraro, respectively. Out of 198 genotypes tested in the greenhouse, 31% exhibited common resistance for Kubsa and mixed stripe rust isolate. Only 8966 of the SNPs were polymorphic, only these were used for association mapping analysis. These markers spanned an average density of 3.47 cM per marker, with the poorest density on the D genome. Almost half of these markers were on known chromosomes, but had no position on the consensus map of bread wheat. Analysis of population structure revealed the existence of three clusters and the estimated genomic wide Linkage Disequilibrium (LD) decay in this study ranged from 0 to 50 cM. 53 SNPs in ten genomic regions located on wheat chromosome 1AL, 2AL, 2BL, 2DL, 3BL, 4BL, 4DL, 5AS, 7AL and 7BL were identified. Thirty nine SNP markers in five genomic regions at Kulumsa and 14 SNP markers in six genomic regions at Meraro explained more than 25.5% and 35.1% of phenotypic variability respectively. For seedling stage, 21 markers in ten genomic regions located on wheat chromosomes 1B, 2A, 2B, 3A, 3B, 4B, 4D, 5A, 6B and 7B were associated with resistant. These loci may be useful for choosing parents and incorporating new resistance genes into locally adapted cultivars.