The University of Queensland, Queensland Alliance for Agriculture and Food Innovation (QAAFI)
Naveenkumar,Athiyannan, Sambasivam, Periyannan, Olga, Afanasenko, Olga, Mitrofanova, Gregory, Platz, Elizabeth, Aitken, Rod, Snowdon, Evans, Lagudah, Lee, Hickey, Kai, Voss-Fels, , , , , , , , , ,
Leaf rust (LR) is an important wheat disease and deployment of resistant cultivars is the most viable strategy to minimise yield losses. We evaluated a diversity panel of 295 bread wheat accessions from the N. I. Vavilov Institute of Plant Genetic Resources (VIR), St Petersburg, Russia for LR response and performed genome-wide association studies (GWAS) using 10,748 polymorphic DArT-seq markers. The diversity panel was evaluated at the seedling and adult plant growth stages using three prevalent Australian P. triticina pathotypes. GWAS applied to 11 phenotypic data sets identified a total of 52 significant marker-trait associations representing 31 quantitative trait loci (QTL). Among them, 29 QTL were associated with adult plant resistance (APR). Of the 31 QTL, 13 were considered potentially new loci, whereas 4 co-located with previously catalogued Lr genes and 14 aligned to regions reported in other GWAS and genomic prediction studies. One seedling LR resistance QTL located on chromosome 3A showed pronounced levels of linkage disequilibrium among markers (r2 = 0.7), indicative of a high allelic fixation. Subsequent haplotype analysis for this region found 7 haplotype variants, of which 2 were strongly associated with LR resistance at the seedling stage. Similarly, analysis of an APR QTL on chromosome 7B revealed 22 variants, of which 4 were associated with resistance at the adult-plant stage. Most of the lines in the diversity panel carried 10 or more combined resistance-associated marker alleles, highlighting the potential of allele stacking for long-lasting resistance.
The University of Georgia (UGA)
Suraj Sapkota, James Buck, Jerry Johnson, John Youmans
Leaf rust disease, caused by the fungal pathogen Puccinia triticina, is a major biotic constraint of wheat production worldwide. Genetic resistance is the most effective, economic, and environmentally safe method to control and reduce losses caused by this disease. More than 70 leaf rust resistance genes have been identified and mapped to specific chromosomes; however, continuous evolution of new leaf rust races requires constant search for new sources of resistance with novel QTL/genes. The objectives of this study were to identify sources of resistance, and to map genomic loci associated with leaf rust resistance using genome wide association study (GWAS) approach. Phenotypic evaluation of 297 spring wheat genotypes against a prevalent race of leaf rust in Georgia revealed that most of the genotypes were susceptible, and only 24 genotypes were found resistant. Furthermore, GWAS detected 10 markers on chromosomes 2A, 2B, 6A, 7A, and 7B significantly associated with leaf rust resistance. A marker on chromosome 7AS was identified revealing a novel genomic region associated with leaf rust resistance. The new identified sources of resistance and QTL could be used in wheat breeding programs to improve leaf rust resistance.
State Key Laboratory of Crop Stress Biology for Arid Areas and College of Plant Protection, Northwest A&F University, Yangling
Lijing Pang, Pu Yuan, Shoujun Hu, Jie Liu, Zhensheng Kang
Pathogens, whatever their types, develop at the expense of the nutrients generated by host and it is largely assumed that classical sources turn into sinks when colonized by pathogens. Sugar appears to be the major carbon and energy source transferred from the host to pathogens. Uptake, exchanges and competition for sugar, at biotrophic interfaces, are controlled by membrane transporters and their regulation patterns are essential in determining the outcome of plant-fungal interactions. However, mechanisms of transport and transporters involved in carbon partitioning between organisms are still poorly understood.
In this study, a wheat sugar transporter protein (STP) gene, TaSTP1, was cloned from a wheat-Puccinia striiformis f. sp. tritici (Pst) interaction cDNA library. Transcripts of TaSTP1 were up-regulated in wheat leaves that were infected by Pst or had experienced exogenous ABA and certain abiotic treatments. Heterologous mutant complementation in Saccharomyces cerevisiae revealed that TaSTP1 transports a broad-spectrum monosaccharides including glucose, fructose, mannose and galactose. Transient expression in Nicotiana benthamiana and Arabidopsis protoplasts suggested that TaSTP1 is localized in plasma membrane. Yeast two hybrid and bimolecular fluorescence complementation (BiFC) validated oligomerization of TaSTP1. Knocking down TaSTP1 using the barley stripe mosaic virus-induced gene silencing system reduced the susceptibility of wheat to the Pst virulent pathotype CYR31. Hyphal abnormality was significantly observed in VIGS plants. These results suggest that TaSTP1 may directly or indirectly participate in sugar transport in the wheat-Pst interactions and exert influence on suagr supply of Pst.
Laboratoire de Biologie, Eau et Environnement, département d'écologie,university of 8 mai1945 Guelma, Algeria
Epidemics of stripe (yellow) rust on wheat and triticale fields of Algeria in 2016. Wheat and triticale fields in 69 localities from the eastern regions of Algeria were assessed for epidemics, which started in early march to late may corresponding to booting stage up to early dough stage of the alternative type crop. The infection had incidences ranging from 30 to 100% and severities of 30 to 70%. The newly released cultivar Ksar sbahi was infected up to 10%. The old improved durum cultivars HAR3116 (SHA7/KAUZ) and HAR1407 (COOK/VEES//DOVES) were rust-free at a number of locations. In the Amhara region, the wheat cultivars were at stem elongation to flowering with disease incidences of 50-100% and severities of 30-90%. The oldest cultivar ET 13 A2 was severely infected in the north Shewa zone of Amhara region. Triticale cultivar Logaw Shibo was susceptible at elevations above 2700 m and showed trace reactions at elevations below 2500 m. The local bread wheat cultivar grown in all wheat growing areas was only slightly affected by the disease. Yellow rust was rarely recorded in the Tigray region. Severe epidemics were recorded in the highlands and even at lower elevations where it is not commonly found on wheat.
Ethiopian Institute of Agricultural Research
Information about changes associated with advances in crop breeding is essential for understanding yield-limiting factors and developing new strategies for future breeding programmes. Thirty-six durum wheat varieties released since 1966 were evaluated in three replications of the Randomized Complete Design at Debre Zeit and Akaki, Ethiopia during the 2016 cropping season to estimate the amount of genetic gain made over time in grain yield potential, yield-associated traits and in protein content. Analysis of variance revealed significant differences among varieties for all 16 quantitative traits, protein content and protein harvest in Kg ha-1 at each of the locations. Grain yield varied between 1.66t ha-1 for Arendato released in 1966 to 3.90t ha-1 for Megenagna released in 2012 with mean of 2.952t ha-1 at Debre Zeit. At Akaki yield range was between 2.45 and 5.04t ha-1 with mean of 3.992t ha-1. 25 varieties surpassed Arendato (3.754t ha-1) at this location. In the combined ANOVA significant difference between the varieties was observed only for spike length, spikelets spike-1, grains spikelet, grains spike-1, plant height, days to flowering, thousand grain weight and hectoliter weight. Varieties specifically adapted to only one of the locations, widely adapted varieties and varieties not adapted to any of the locations were identified. Regression analysis revealed that grain yield has increased by 22kg ha-1 year-1 since 1966; an increase of 40.6% over yield in 1966. This was accompanied with a significant decline of 11.4% in spike length, 6.7% in spikelets spike-1, 17.9% in protein content and 31.2% in protein yield ha-1 and a significant increase of 41.1% in grains spikelet-1, 32.9% in number of grains spike-1, 22.3% in thousand grain weight, 17.8% in grain filling period, 23.9% in seed growth rate, 40.1% in grain yield production rate, 7.9% in harvest index.
Research Institute of Crop Husbandry, Azerbaijan
ATIF,ZAMANOV, Konul, Aslanova, , , , , , , , , , , , , , , , , , , , , , , , , ,
Rust diseases are considered the main stress factors that limit wheat productivity in the Azerbaijan. The studies on the impact of rust diseases on physiological processes at reproductive vegetation period is of very importance with view of evaluating size of yield and quality of the studied genotypes. For this purpose the studies focused on bread wheat genotypes (Triticum aestivum L.), which differ sharply by architectonics, biological peculiarities and resistance to rust diseases. Comparative evaluation of the studied genotypes by physiological and quality parameters has been undertaken in two options: over plants infected with diseases in natural background, and over healthy plants (fungicide sprayed plants). Area of photosynthesis apparatus of leaf story (18,3-50,2 sm2) of the studied wheat genotypes changes in wide interval. Infestation level of leaves with yellow rust (Puccinia striiformis West.) in wheat genotypes grown in natural infection background fluctuates between 5MS-40S in ontogenesis, but between 10MS-90S with brown rust (Puccinia recondita Desm.).
High level of infection with rust diseases leads to reduced size of leaf assimilation area and defoliation. Reduction of these dimensions makes up 10-90% in lower story leaves of genotypes infected with rust diseases, but 20-30% in upper story leaves. Genotypes with large and bending leaves subject to this disease more frequently. Value of photosynthesis intensity in ontogenesis at upper story leaves of the genotypes infected with rust diseases at natural background fluctuates between 6-18 ?mol CO2 .m-2.s-1 depending on level of infection, but in healthy plants between 16-29 ?molCO2 .m-2.s-1. Negative impact of these diseases on normal course of plant physiological process ultimately causes is reflected in yield and quality parameters.
Seed and Plant Improvement Institute, Agricultural Research, Education and Extension Organization, Karaj, Iran.
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Stripe rust of wheat, caused by Puccinia striiformis f. sp. trirtici (Pst) is an important disease in many parts of Iran. Over last two decades several epidemics have occurred in Iran causing the breakdown of widely utilized sources of resistance in wheat cultivars. Fifty isolates were collected from different parts of Iran during 2017. Eight isolates of Pst. from 2017 have been processed to date for race analysis. Infection types were assessed on a 0-9 scale 16 and 18 days after inoculation using a scale similar to that described by McNeal et al. (1971). Infection types (ITs) 7 to 9 were regarded as virulent (susceptible) and lower than 7 were avirulent. Pathotypes 102E158A+,Yr27; 6E158A+,Yr27; 102E158A+,Yr27; 166E154A+,Yr27; 38E174A+; 38E158A+,Yr27; 238E190A+,Yr27 and 38E190A+,Yr27 were identified. Pathotype 238E190A+,Yr27+ (from West of Iran) was more aggressive during this study. Plants with Yr1, Yr4, Yr5, Yr10, Yr15, Yr24 and YrSP were resistant to all pathotypes. Pathotypes with virulence on plant with gene/s Yr2, Yr6, Yr7, Yr8, Yr9, Yr25, Yr26, Yr27, Yr32, YrSD, YrSU, YrND and YrA were more common. Seedling tests of Iranian wheat cultivars to race 238E190A+,Yr27+ showed that the new released cultivars that included Parsi, Baharan, Bahar, Pishgam, Zareh, Urom, Maihan, Dena, Haydarei and Shabrang were resistant to the new aggressive race with virulence on plants with Yr27.
Seed and Plant Improvement Institute, Agricultural Research Education and Extension Organization (AREEO), Karaj, Iran
The basidiomycetous fungus, Puccinia graminis f. sp. tritici (Pgt) causes stem rust disease as one of the most destructive wheat pathogens, worldwide. TTKSK and other Pgt races under Ug99 race group are considered as major threats to wheat production in east Africa and CWANA region by defeating the stem rust resistance gene Sr31, while its ineffectiveness was reported in Iran in 2007. Race TKTTF of Pgt caused a severe stem rust epidemic in southern Ethiopia in 2013, and was spread to Europe through 2016 Sicily outbreak. This research describes race identification of Iranian isolates collected during the widespread distribution of stem rust in 2014-16. Purified urediniospores of 123 Pgt isolates were separately inoculated on seedlings of 20 North American differential wheat cultivars carrying different Sr resistance gene/s. Infection types were recorded at 14 days post inoculation (dpi) using Stakman et al. 0-4 scale. Based on the letter code nomenclature, we identified the Pgt races TKTTF, TTTTF, TTKSK, TTKTK, PKTTF, TKSTF, PKSTF, PKTTC, PTRTF, PTTTF, PKSTC, TTRTF, TKSTC and PKRTF in Iran. TKTTF and TTTTF were determined as prevalent Iranian Pgt races. This is the first report of race TTKTK, a new variant of Ug99 race group with virulence on Sr31 and SrTmp resistance genes, in Iran. Since TTKTK primarily occurred in south west of Iran, the migration route for this new race seems to be similar to race TTKSK. The high race variation observed in this study could indicate a high genetic diversity among P. graminis f. sp. tritici populations in Iran, as a wheat center of origin.
Crop Diseases Research Institute, PARC Substation, Murree Pakistan
Sufyan,Muhammad, Abid Majeed, Satti, Munir, Anjum, Fayyaz, Muhammad, Atiq ur Rehman, Rattu, Imtiaz, Muhammad, , , , , , , , , , , , , , , , , ,
225 Puccinia striiformis f.sp. tritici isolates collected from wheat growing areas of Pakistan during 2013-2016 were analyzed using 18 near isogenic yellow rust differentials. Seventy eight races were identified among collection in which 20 were common (n > 2). Rest of the races were very rare and encountered only once (n=1). Races 574212, 574232, 474232, 474233, 574213 and 434232 were most frequent (n> 15). Pathogenic diversity analysis of the collection reveal high diversity (H =3.57) of the P. striiformis population of pakistan. On the basis of phenotypic response to yellow rust genes, the most frequent races could be grouped into 5 diverse groups. Distinct grouping was also observed in rarely encountered isolates. Most of the races were highly complex and 80% isolates had complexity ranging from 8 to 11. Virulence frequency for Yr6, Yr7, Yr8, Yr17, Yr27, Yr43 & YrExp2 remained above 80% while that of Yr1, Yr9 and Yr44 remained over 40%. Partial virulence was detected for Yr5, while virulence to Yr10, Yr15, YrSP was found in < 4% isolates. Paper discuss spatial and temporal distribution of P. striiformis races in Pakistan.
Ravi Singh, Karim Ammar
Stripe rust, caused by Puccinia striiformis tritici (Pst), continues its evolution towards virulence to race-specific resistance genes. Identification of Mexican Pst isolates MEX16-03 and MEX16.04 that changed infection types of Yr10 testers from 1 to 9 and for Yr24 (=Yr26) testers from 3 to 9 indicated that a mutation for virulence to these resistance genes has occurred in a predominant race detected in 2014 and maintained at CIMMYT as MEX14.191 and at INIFAP as CMEX14.25. Isolate MEX14.191 was responsible for the susceptibility of popular varieties Nana F2007 and Luminaria F2014 grown in central Mexican highlands. Isolate MEX16.04 has the following avirulence/virulence formula: Yr1, 5, 15, SP/Yr2, 3, 6, 7, 8, 9, 10, (17), 24, 26, 27, 28, 31, 32 using the Avocet near-isolines and other known testers. Virulence to Yr10 and Yr24 (=Yr26) were also confirmed by testing seedlings of cultivars Moro (Yr10), Chuanmai 42, and Neimai 836 (Yr24). Seedling tests carried on 200 bread wheat, 550 durum, and 460 synthetic hexaploid wheats with their respective durum parents from CIMMYT collection indicated that MEX16.03 and MEX16.04 do not represent a major threat because a majority of the lines remained resistant to these isolates. However, it is worth mentioning that durum cultivars, such as Khofa, Desert King, Anatoly, Movas, and Llareta INIA, and 10 primary synthetic hexaploid or synthetic-derived bread wheats that were resistant to MEX14.191 became susceptible to MEX16.03 and MEX16.04. Our results indicate that resistance gene Yr10 was absent and Yr24 occurred in low frequency in CIMMYT bread wheat germplasm. A majority of CIMMYT durum wheat possibly carried Yr24 in combination with other effective gene(s).