The University of Agriculture, Peshawar, Pakistan
Muhammad Khan, Muhammad Imtiaz, Zahoor Swati, Annemarie Justesen, Sajid Ali
Yellow rust caused by Puccinia striiformis is an important disease in Pakistan. The population structure of P. striiformis in the North Eastern Himalayan region of Pakistan have been shown to be genotypically diverse with potential role of sexual recombination (Ali et al., 2014b), while lesser diversity in the Southern districts of Khyber Pakhtunkhwa (KP)(Khan et al., 2015). This study was designed for the first time to assess disease status and analyze population structure of P. striiformis across three distant parts of Northwestern Pakistan i.e., Bajaur in North Western Agency and Swat and Buner in Malakand Agency, and was compared with other Pakistani populations. Depending on the intensity of infections caused by the pathogen in the tested varieties and breeding lines, the severity of the disease ranged from 5% to 100% during 2015. Yellow rust severity was the maximum on Morocco (100%), Gomal (100%) and KPWYT-18 (80%) and moderate on Ghanimat-e-IBGE (10%) and PS-2008, PS-2013, Tatara and Millat with 20% severity. A total of 81 single lesion samples collected on infected varieties were genotyped with 18 microsatellite markers. From these, 63 distinct multilocus genotypes (MLGs) were detected; 15 single lesion samples collected from Buner produced 15 distinct MLGs signifying very high diversity. A high genotypic diversity with clear signature of recombination was detected across all the three locations. Buner (100%) had the maximum diversity followed by Swat (97%) and Bajaur (91%). The observed diversity was almost equal to other Northeastern Himalayan populations of Pakistan, while it was high when compared to some southern populations of KP (genotypic diversity of 0.895) and other worldwide clonal populations (Ali et al., 2014a). The high diversity and recombinant population structure suggested potential role of sexual reproduction in these areas, which needs to be further explored to establish the origin of diverse virulence pattern in Pakistan.
Instituto Nacional de Tecnologia Agropecuaria (INIA), Estaci?n La Estanzuela, Ruta 50, Km 11, Colonia, Uruguay
Vanesa,Domeniguini, N?stor, Gonz?lez, Richard, Garcia, Carolina, Saint-Pierre, Pawan, Singh, Mart?n, Quincke, Silvia, Pereyra, Silvia, Germ?n, , , , , , , , , , , , , ,
Since 2014 CGIAR-WHEAT Program has promoted the establishment of a network of field-based Precision Wheat Phenotyping Platforms (PWPP) to expand the existing collaborations between CIMMYT, ICARDA and National Agricultural Research System partners. The main goals are improving the quality of data collected and shared among institutions to enhance and accelerate the international wheat breeding, and promote synergism with the private sector and nongovernmental organizations. In 2015, the PWPP-Uruguay was established to test genotypes for multiple diseases: leaf rust, Fusarium head blight and Septoria tritici blotch. These diseases are phenotyped each year in separate field trials artificially inoculated with pathogen isolates identified as representatives of the pathogen regional population. Wheat material is sowed in plots with susceptible checks every 50 entries. Disease severity and other variables related to the disease development are measured using standard international scales at dates when the expression of plant resistance is optimal. In the first three years of the platform, more than 1500 genotypes were screened per year. These materials had diverse origins (more than eight institutions, public and private, from eight countries) and diverse types: from recent commercialized to ancient cultivars, advanced lines, International CIMMYT nurseries, mapping populations or panels. Highly resistant genotypes to multiple diseases could be selected. At the present time, we are developing and adopting advanced phenotyping methods, combining remote sensing and image analysis, and exploring their adaptation to breeding constraints. Also, extension activities as internships, training courses and student projects are being developed. Major future prospects are the enhancement of data and germplasm exchange between platform partners and the PWPP network and the involvement in collaborative phenotyping/genotyping breeding projects.
University of Seville
Solis,Ignacio, , , , , , , , , , , , , , , , , , , , , , , , , , , ,
Leaf rust is an important worldwide disease on wheat caused by the fungus Puccinia triticina. Great infections on durum wheat occurred in Southern Spain in the 2000s but diminished in recent years due to deployment of resistant varieties and application of fungicides by farmers. A leaf rust survey was carried out from the 2009-15 period to monitor the virulence spectrum of the prevailing pathotypes. A total of 84 leaf rust isolates were collected on durum wheat fields. From those, single culture were obtained and used to inoculate a set of 27 differential isolines of the susceptible variety Thatcher. In addition 8 durum varieties with known Lr genes were also included.
The main highlight is that the resistance conferred by the popular Lr14a gene was broke up in 2013, but since then virulence to this gene is not widespread. In total, 23% of the isolates were virulent to the lines containing Lr14a. Lr1, Lr3, Lr3bg, Lr16, Lr24, Lr26, and Lr28 are very effective. Lines carrying Lr2c, Lr10, Lr14b, Lr20, Lr23, and LrB displayed susceptibility to most isolates. The durum varieties Jupare (Lr27+Lr31), Guayacan (Lr61), Storlom (Lr3+) and Camayo (LrCam) are also resistant against all isolates tested. Diversification of Lr genes is needed in the coming varieties to delay the appearance of new virulent races.
ICAR-Indian Institute of Wheat and Barley Research
Sudheer Kumar, P.L. Kashyap, Gyanendra Pratap Singh
Yellow rust of wheat caused by Puccinia striiformis Westend. is one of the important diseases of wheat in India. In north Indian states it spreads quite fast due to favourable temperature and moisture prevailing in these states during major part of crop growth (November-mid March). In spite of favourable weather, proactive survey and surveillance and advisories issued in time resulted successful management of yellow rust in India during past four decades. Even large scale cultivation of varieties like HD 2967 in about 12 million ha past two years did not result any losses. Three spots of initial foci near foot hills in Punjab have been identified and are monitored regularly. Any sign of yellow rust is controlled effectively with the foliar sprays of fungicides like propiconazole @ 0.1%. Use of mobiles phones and internet services is regularly done for transfer of information on wheat crop health and suggestions for proper management. Strategic planting and sowing of wheat in which newly released high yielding yellow rust varieties helped in reducing the yellow rust inculum build up. Regular monitoring of wheat health via weather forecasts take place after every fortnight from December to March. During 2016-17 crop season, yellow rust was effectively managed and its occurrence was delayed in Punjab, Haryana and Uttarakhand states. Two new pathotypes, 110S 119 and 110S 84 developed recently were used for evaluation of entries of wheat yield trials during 2016-17 at hot spot locations. The new varieties in pipe line of identification and release are tested against yellow rust. The most critical period for yellow rust management remained from December till mid February.
Jianping Zhang, Peng Zhang, Robert Park, Narayana Upadhyaya, Robert McIntosh, Sambasivam Periyannan, Brande Wulff, Burkhard Steuernagel, Evans Lagudah
Evolution of rust pathogens continues to pose challenges to global wheat production. Major resistance (R) genes, which encode proteins of the NBS-LRR (Nucleotide-binding site, leucine-rich repeat) family, have been a valuable resource for breeders to minimise yield losses from infection. Many wheat varieties harbor numerous R genes that could be identified and cloned in order to engineer more sustainable disease control. The advent of targeted gene enrichment and next-generation sequencing (NGS) has allowed rapid cloning of specific R genes, thus enhancing efforts to pyramid these genes and investigate their underlying resistance mechanisms. Several R genes present different phenotypes in certain genetic backgrounds, and cloning them would be an important step towards uncovering their interactions. Hybrid necrosis is one such phenotype observed in crosses of wheat genotypes involving the R gene Lr13 and complementary genes, Ne1 and Ne2, occurring in different allelic forms. It was recently concluded that Lr13 and an allele of Ne2 are actually the same gene based on genetic and mutational studies. The capability of Lr13 to confer both leaf rust resistance and hybrid necrosis cannot be answered without first cloning it. The lack of tightly linked markers coupled with the proximal 2BS chromosomal location of Lr13 does not make it easily amenable to map-based cloning. The NGS-based pipeline MutRenSeq (mutagenesis and R-gene enrichment sequencing) was used on EMS (Ethyl methanesulfonate) induced, susceptible Lr13 mutants along with support from comparative genomics to ascertain candidate gene sequences for Lr13, which are at advanced stages of screening and confirmation. Definite proof that a single gene is involved will only come with transformation studies when the cloned Lr13 candidate transformed into a susceptible line confers both a resistance phenotype in the transgenic line and a necrotic phenotype in the offspring of crosses between the transgenic line and a line possessing Ne1.
National Agronomic Institute of Tunisia
Sana Kamel, Elhem, Elfahem, Wissal Feriani, Hanen Sbei
In order to identify sources of resistance to tan spot caused by Pyrenophora tritici-repentis, 359 local wheat accessions were evaluated for reaction to the Oued-Mliz isolate in controlled conditions and in the field. Two and three assessments were carried out at the seedling and adult stages, respectively. There was a highly significant accession effect and 4.2% of accessions were highly resistant in both controlled conditions and the field. Assessments at the seedling stage were positively correlated with each other, and assessments in the adult stage were also positively correlated. However, assessments at the seedling stage were negatively correlated with those at the adult stage. One hundred and fifty five accessions with known origins (from 15 localities belonging to four districts) were projected on a graph defined by the two axes: reactions at the seedling stage and reactions at the adult stage. After placing the average reactions at the seedling and adult stages on the graph, four groups of accessions were obtained: accessions that were resistant to both stages, accessions that were resistant at the adult stage only, accessions that were resistant at the seedling stage only, and accessions that were susceptible at both stages. All four groups were found in each district. However, considering localities, reactions of accessions were highly variable. For example, accessions originating from Menzel Hbib were genetically variable and were represented in each of the four groups, whereas accessions from Sidi El Hani were all resistant at both stages. Further work is needed to study the genetic variability within and between localities and to better understand the resistant accessions.
Mohammad Kassem, Ghinwa Lababedi, Naim Al-Husien
Leaf rust is the most common rust in wheat production areas of Syria and causes significant annual yield losses. Using genotypes with durable resistance is the most economical way of controlling the disease. One of the best-known leaf rust resistance genes is Lr46 that confers a slow rusting type of adult plant resistance. The main objective of this study was to identify Lr46 in durum wheat genotypes using morphological and molecular markers. Thirty-two durum wheat genotypes were evaluated for response to leaf rust at the seedling and adult plant stages. Twelve genotypes (37.5%) were resistant (R), 10 (31.25%) were moderately resistant (MR), seven (21.87%) were moderately susceptible (MS), and three (9.37%) were susceptible (S). Molecular marker analyses using SSR marker wmc44 showed that 16 genotypes (50%) carried Lr46/Yr29. The genotypes possessing the marker linked to Lr46/Yr29 could be used for selection of Lr46/Yr29 in breeding for slow rusting resistance in durum.
Levent Ozturk, Ismail Cakmak
Zinc (Zn) deficiency is an important health problem worldwide, affecting about two billion people, especially children and women. Zinc deficiency related diseases are more prevailing in developing countries because populationa rely on cereals (i.e., wheat, rice and maize) as a staple food which are inherently low in micronutrients. Zinc concentration in cereal grains can be improved by genetic or agronomic biofortification. Optimized applications of soil and foliar Zn fertilizers has been found effective for cereals like wheat and rice but not significantly in maize. Current study focuses to elucidate the physiological reasons behind the poor response of maize to foliar applications compared to wheat. Experiments with stable isotope of Zn (70Zn) revealed the differences in leaf uptake, root and shoot translocation of foliar-applied Zn in wheat and maize. The results suggested that wheat has greater capacity for leaf absorption and translocation of foliarly applied Zn compared to maize. The increased leaf Zn uptake and localization in wheat was confirmed by a visual demonstration using Zn-responsive fluorescent dye Zinpyr and fluoresce microscopy. This study provides valuable information to maximize the uptake and deposition of foliarly applied Zn to cereal grains.
Instituto Nacional de Investigaci?n Agropecuaria (INIA) La Estanzuela
Paula Silva, Clara Pritsch, Miguel Raffo, Silvia Pereyra, Silvia German
Wheat stem rust (SR), caused by Puccinia graminis f. sp. tritici, (Pgt) is considered one of the most destructive diseases of the wheat crop. As Sr24 and Sr31 are the most widely used resistance genes in the Southern Cone of America, wheat crops in this region is under threat of SR outbreaks posed by the potential migration of virulent Pgt Ug99-lineage races (Ug99+). Efforts have to be made to develop adapted lines resistant to Ug99+. Genes Sr26, Sr32 and Sr39 are effective to both Ug99+ and local races of the pathogen. This work is aimed to pyramid two and three of the resistance genes in two locally adapted wheat cultivars (G?nesis 2375 and G?nesis 6.87). Donor lines of Sr26, Sr32 and Sr39 (developed by I. Dundas, University of Adelaide, Australia) and molecular markers Sr26#43, csSr32#1 and Sr39#22r (developed by R. Mago et al., University of Adelaide) were used. Lines with two-gene combinations were developed in two steps. First, tree-way crosses were made by crossing heterozygous F1 plants (derived from crossings donor lines) to either one of the two adapted wheat cultivars. Subsequently, tree-way F1 plants were genotyped and only those with two-gene combinations were backcrossed (BC) twice to the adapted cultivars. Among three-way F1 plants, two-genes combinations were confirmed for Sr26+Sr32 (8 out of 31), Sr26+Sr39 (2 of 115) and Sr32+Sr39 (26 out of 103). In the BC1F1 generation, Sr26+Sr32, Sr26+Sr39 and Sr32+Sr39 combinations corresponded with 9, 9 and 45 out of 99, 27 and 241 plants, respectively. In 2017, 1345 BC2F1 plants are being grown to obtain BC2F2. We plan to intercross plants with two-gene combinations to obtain lines with the three genes which will be used as sources of resistance to develop cultivars with presumably longer lasting resistance to wheat SR.
CREA-Research Centre for Cereal and Industrial Crops
Elisabetta Mazzucotelli, Oadi Matny, Antonietta Saccomanno, Raffaella Battaglia, Francesca Desiderio, Agata Gadaleta, Nicola Pecchioni, Pasquale De Vita, Giovanni Laido, Luigi Cattivelli, Brian Steffenson
The recent emergence of new widely virulent and aggressive strains of rusts (particularly stripe and stem rust) is threatening Italian durum wheat (Triticum turgidum L. var. durum) production, especially under the trend of higher temperature and humidity. A big effort has been undertaken to explore the genetic variability for resistance to these fungal pathogens and discovering novel resistance genes. In particular, a wide set of tetraploid wheat lines was genotyped with several thousands of SNP markers and used for association mapping. This large collection consisted of a group of durum wheat cultivars, produced from the beginning of the last century up to now, a collection of wild emmer wheats (T. dicoccoides), and lines belonging to other wild and domesticated tetraploid subspecies, as a large untapped source of genetic diversity. In a tight cooperation with the University of Minnesota, this collection was evaluated for reaction to several races of stem and stripe rust pathogens in both controlled greenhouse and field conditions. Among the genotypes belonging to the collection are parents of segregating populations which were used for the validation of mapping results. Novel resistance loci were identified, that can be incorporated into new durum varieties through breeding programs. The QTLs found in this study, together with those available in literature, were projected to the recently sequenced durum wheat genome in order to define more precisely the chromosome regions and candidate genes involved in resistance to rusts. Lines which were resistant to multiple races of rust pathogens were also found among both T. dicoccoides and durum wheat cultivars as a source of resistance genes, whose cloning will be undertaken based on the results here obtained.
This study was supported by the Italian Ministry of Foreign Affairs and International Cooperation, with the special grant RES-WHEAT.