Puccinia Graminis Tritici Research Articles

Multiple resistance genes to leaf and stem rust in Brazilian wheat varieties ‘BRS194’ and ‘Toropi’

Leaf (Puccinia triticina; Pt) and stem (Puccinia graminis tritici; Pgt) rust are important constraints to wheat production. The leaf and stem rust resistance in the Brazilian wheat varieties ‘Toropi’ and ‘BRS194’ was evaluated using a ‘Toropi/BRS194’ doubled-haploid (DH) population. Parents evaluated at the seedling stage with Pt race MCJ-HN displayed infection type (IT) = ;1 for ‘BRS194’ and IT = 3 for ‘Toropi’. The DH progeny fit a 1R:1S ratio, indicating a single Lr gene in ‘BRS194’ was effective against race MCJ-HN. Adult plant testing with isolate 18-96-1 CCDS found that ‘BRS194’ displayed an IT = 3 and ‘Toropi’ IT = 1−, with segregating progeny consistent for multigenic adult plant resistance in ‘Toropi’. The parents and DH progeny were screened for the 1BL.1RS translocation (Sr31) with marker PE061, with ‘Toropi’ negative and ‘BRS194’ positive for the presence of Sr31. ‘BRS194’ was also tested against Pgt races MCCF, QTHJ, RHTS, RTHJ, TMRT, TPMK, and TTKSK at the seedling stage. BRS194 was resistant to all Pgt races, and an IT = 0 to TTKSK suggested the presence of Sr36. The presence of Sr36 in ‘BRS194’ was supported by the molecular marker STM773-2 (+) and ‘Arthur 71’ (Sr36 carrier) in its pedigree. Most resistant lines carried the Sr36-associated allele of STM773-2, while a few did not, indicating the presence of a second gene conferring resistance to TTKSK. Seedling resistance to Pgt in ‘Toropi’ was effective against races RHTS, MCCF, QTHJ, and RTHJ, postulated to be Sr9e. The variety ‘BRS194’ has effective rust-resistance genes that can be used in wheat-breeding programmes.

Genetics of stem rust resistance in four popular durum wheat cultivars

A study was conducted to understand the mode of inheritance and extent of diversity of stem rust resistance in four popular durum wheat cultivars of central India viz., HI 8498 (Malav Shakti), HI 8663 (Poshan), HI 8713 (Pusa Mangal) and HI 8737 (Pusa Anmol) using Puccinia graminis tritici (Pgt) pathotypes 15-1 (123G15) and 40-3 (127G29). These cultivars were crossed with susceptible parents i.e., Motia and Malvi Local and were also crossed among themselves in half diallel fashion. The F2 and F3 segregation data revealed that a single dominant gene each controlled resistance to the pathotype 40-3 in HI 8713 and HI 8663, while two dominant genes each governed resistance to this pathotype in HI 8737 and HI 8498. A single dominant gene each conditioned resistance to the pathotype 15-1 in all the four cultivars. The F2 segregation data of the intercrosses among the resistant parents showed that three different resistance genes controlled resistance among four cultivars against each Pgt pathotype 40-3 and 15-1. These genes seem to be different from the most commonly postulated stem rust resistance genes in Indian durum wheat germplasm viz., Sr11, Sr12, Sr7b and Sr9e which are ineffective/less effective against the test pathotypes. Hence, the genes identified in the present study can be utilized in broadening the genetic base of stem rust resistance in Indian durum wheat.

Pathogenic Variability of Wheat Stem Rust Pathogen (Puccinia graminis f. sp. tritici) in Hararghe Highlands, Ethiopia

Wheat is one of the important major crops of Hararghe Highlands. It is third in land coverage and total production after sorghum and maize. However, the wheat stem rust disease is threatening production of wheat in this region. So, this research was conducted with the following objective: to determine the population of Puccinia graminis f. sp. tritici in Hararghe Highlands. A total of 200 fields were surveyed and stem rust samples were collected and transported to Kulumsa Agricultural Research Center for race analysis. Inoculation of differentials carrying resistance genes Sr24 and Sr-Tmp indicated typical low infection types on all isolates. Isolates EH5, EH8, and EH3 from East Hararghe and WH2, WH1, and WH3 from West Hararghe showed high virulence of infection in all differential lines. Ten (10) races were identified by using Puccinia graminis tritici code system: TTGSK, PTJQK, TTSSK, TTKSK, TRSSK, and TTJQK from East Hararghe and TTTSK and TTSQK from West Hararghe zones. Race TTSSK was most frequent (25%) followed by TTKSK (25%) in East Hararghe. Race TTSSK showed 50% frequency of occurrence in West Hararghe zones. The low frequency of occurrences indicated high variability of the races in the survey areas. Therefore, monitoring of populations of pathogens is important for the national and regional research centers. Detection of pathogen virulence evolution and of currently effective resistance genes is necessary and must be applied within a system of resistance gene management.

Inheritance of resistance to Ug99 stem rust pathogen in selected barley lines

Stem rust (Puccinia graminis tritici) race Ug99 is a devastating disease of wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.). Barley is the world's fourth most important cereal crop after wheat, maize (Zea mays L.) and rice (Oryza sativa L.). The seedlings of F2 populations were inoculated 7–10 d after planting and when the first leaf was fully emerged (Feekes stage 1). The observed resistant (R):susceptible (S) ratio of the F2 populations HKBL-1385-13×08-UT-86 (χ20.05 = 0.480, P ≥ 0.488), HKBL-1385-13×09-N2-19 (χ20.05 = 0.641, P ≥ 0.424), ND2649 × 09-AB-78 (χ20.05 = 1.05, P ≥ 0.309) and ND25882×09-AB-78 (χ20.05 = 3.599, P ≥ 0.058) exhibited Mendelian segregation of 3R:1S suggesting that the resistance is conferred by major genes. In addition, F2 populations derived from the crosses Karne×09-N2-19 (χ20.05 = 1.343, P ≥ 0.246), Nguzo×09-AB-78 (χ20.05 = 0.429, P ≥ 0.512), ND26249×09-N2-52 (χ20.05 = 2.576, P ≥ 0.111) and ND25882×09-AB-78 (χ20.05 = 0.980, P ≥ 0.322) conformed to a phenotypic ratio of 9:7 indicating that there are genes modifying the resistance to Ug99. The results of this study suggest that there are valuable major genes for stem rust resistance that could be used to improve susceptible barley and wheat germplasm.

Sources of resistance to Indian pathotypes of Puccinia graminis tritici and P. triticina in durum wheat

AbstractStem rust and leaf rust are important diseases affecting durum wheat production in India. Inheritance and extent of diversity in resistance were studied in five durum genotypes, viz. ʽB 662', ʽED 2398‐A', ʽHG 110', ʽIWP 5019' and ʽLine 1172ʼ using Pgt pathotypes 40A and 117‐6, and Pt pathotypes 12‐2 and 104‐2. F2 and F3 analyses showed that resistance was conferred by one or two genes in each line. In all, four genes for resistance to 40A, and eight each for pathotypes 117‐6 and 12‐2 were identified among the five genotypes, and three for resistance to 104‐2 among B 662, ED 2398‐A and IWP 5019 were indicated by tests of allelism. Although the gene identities are not known, at least some of them should be different from Sr2, Sr7b, Sr8a, Sr8b, Sr9e, Sr9g, Sr11, Sr12, Sr13, Sr14, Sr17, Sr23 and Sr28; and from Lr3, Lr14a, Lr23 and Lr27 + Lr31. These genotypes enrich the diversity of resistance to stem rust and leaf rust for durum wheat improvement.

Enhanced resistance in wheat against stem rust achieved by marker assisted backcrossing involving three independent Sr genes

Marker assisted backcrossing (MABC) was used to transfer the three stem rust (Puccinia graminis tritici) resistant genes Sr25, SrWeb and Sr50 into the popular Indian wheat cv. HUW234. The donor was the CIMMYT breeding line PMBWIR4, and each of the target genes was marked by a simple PCR assay. A three step screening strategy was adopted: the first screen comprised foreground selection, the second used markers lying close to the introgression borders to reduce the extent of linkage drag, and the last was background selection based on 149 informative microsatellite assays. Based on the background selection outcomes, at the BC1F1 generation the proportion of the genome fixed for cv. HUW234 alleles ranged from 55% to 67%. Three BC1F1 individuals were crossed a second time with cv. HUW234, resulting in the identification of six BC2F3 families carrying all three target Sr genes; the proportion of their genome inherited from cv. HUW234 ranged from 86% to 92%. BC2F4 and BC2F5 material was planted at three different locations under both disease-free and artificially induced epiphytotic conditions. Compared to recurrent parent, the improved versions of cv. HUW234 displayed significantly superior resistance to stem rust, and their agronomic performance was as good as, or even marginally better than that of the source cultivar.

The Accessory Genome as a Cradle for Adaptive Evolution in Pathogens

Pathogens offer many of the most fascinating and well-studied examples of evolution because their speed of adaptation allows observation of evolutionary change within human lifetimes. The rapid evolution observed in pathogenic viruses, bacteria, and fungi affect human, animal, and plant health globally. For example, influenza viruses regularly recombine genes affecting host range, infection pathways, and virulence prior to the emergence of deadly outbreaks [1]. The emergence of antibiotic resistance in bacteria, including highly resistant Staphylococcus aureus strains and the re-emergence of resistant tuberculosis, is well documented [2], [3]. The recent outbreak in Africa of wheat stem rust caused by the Ug99 pathotype of the fungus Puccinia graminis tritici surprised many plant pathologists, who thought this ancient pathogen was defeated during the green revolution [4]. It is clear that pathogens engage host species in a constant race to evolve new defense mechanisms. By extension, we are constantly challenged to find new treatments and better containment measures to protect human health and essential crops.

The Emergence of Ug99 Races of the Stem Rust Fungus is a Threat to World Wheat Production

Race Ug99 of the fungus Puccinia graminis tritici that causes stem or black rust disease on wheat was first detected in Uganda in 1998. Seven races belonging to the Ug99 lineage are now known and have spread to various wheat-growing countries in the eastern African highlands, as well as Zimbabwe, South Africa, Sudan, Yemen, and Iran. Because of the susceptibility of 90% of the wheat varieties grown worldwide, the Ug99 group of races was recognized as a major threat to wheat production and food security. Its spread, either wind-mediated or human-aided, to other countries in Africa, Asia, and beyond is evident. Screening in Kenya and Ethiopia has identified a low frequency of resistant wheat varieties and breeding materials. Identification and transfer of new sources of race-specific resistance from various wheat relatives is underway to enhance the diversity of resistance. Although new Ug99-resistant varieties that yield more than current popular varieties are being released and promoted, major efforts are required to displace current Ug99 susceptible varieties with varieties that have diverse race-specific or durable resistance and mitigate the Ug99 threat.

Development and characterization of wheat-Ae. searsii Robertsonian translocations and a recombinant chromosome conferring resistance to stem rust

The emergence of a new highly virulent race of stem rust (Puccinia graminis tritici), Ug99, rapid evolution of new Ug99 derivative races overcoming resistance of widely deployed genes, and spread towards important wheat growing areas now potentially threaten world food security. Exploiting novel genes effective against Ug99 from wild relatives of wheat is one of the most promising strategies for the protection of the wheat crop. A new source of resistance to Ug99 was identified in the short arm of the Aegilops searsii chromosome 3S(s) by screening wheat- Ae. searsii introgression libraries available as individual chromosome and chromosome arm additions to the wheat genome. For transferring this resistance gene into common wheat, we produced three double-monosomic chromosome populations (3A/3S(s), 3B/3S(s) and 3D/3S(s)) and then applied integrated stem rust screening, molecular maker analysis, and cytogenetic analysis to identify resistant wheat-Ae. searsii Robertsonian translocation. Three Robertsonian translocations (T3AL·3S(s)S, T3BL·3S(s)S and T3DL·3S(s)S) and one recombinant (T3DS-3S(s)S·3S(s)L) with stem rust resistance were identified and confirmed to be genetically compensating on the basis of genomic in situ hybridization, analysis of 3A, 3B, 3D and 3S(s)S-specific SSR/STS-PCR markers, and C-banding. In addition, nine SSR/STS-PCR markers of 3S(s)S-specific were developed for marker-assisted selection of the resistant gene. Efforts to reduce potential linkage drag associated with 3S(s)S of Ae. searsii are currently under way.

Effect of fungicide on the development of wheat stem rust and yield of wheat varieties in highlands of Ethiopia

Stem rust caused by Puccinia graminis f.sp tritici Erik. & E. Henn. is a highly destructive disease of wheat (Triticum aestivum L.). The effects of fungicide application on stem rust (Puccinia graminis tritici) epidemics and yield of three bread wheat varieties varying in reaction to the disease were studied in two major wheat growing and stem rust prone districts (Agarfa and Sinana) of Bale, Ethiopia. Disease onset was late, generally after ear emergence, at both locations; but stem rust severity increased at high rates and terminal severity levels up to 81,72 and 37% at Agarfa, and up to 37, 32 and 14% at Sinana were recorded on the varieties Sirbo, Maddawalabu and FH4-2-11, respectively. The rates of infection and AUDPC values of stem rust on the varieties were significantly (P

Trigo EMBRAPA 41: Nova cultivar para Minas Gerais, Goiás e Distrito Federal

A cultivar de trigo (Triticum aestivum L.) EMBRAPA 41 foi criada pela Embrapa-Centro de Pesquisa Agropecuária dos Cerrados (CPAC), em Planaltina, DF. Essa cultivar é o resultado da seleção realizada na descendência do cruzamento entre PF 813 e Polo 1; foi avaliada na fase experimental como linhagem CPAC 88118. A nova cultivar foi recomendada, pela Comissão Centro-Brasileira de Pesquisa de Trigo, para cultivo irrigado durante a estação seca, em 1995, nos estados de Minas Gerais e Goiás e no Distrito Federal. Essa cultivar destaca-se por apresentar estatura média, ciclo precoce, alto potencial de rendimento e por sua superior qualidade industrial. Nas avaliações de resistência a enfermidades, apresentou reação de resistência em relação à ferrugem-do-colmo, causada por Puccinia graminis tritici.

Reaction of Turkish barley accessions to Canadian barley pathogens

Recent changes in the virulence patterns of Canadian barley pathogens have necessitated the search for new sources of genetic resistance in barley. Evaluation of 176 Turkish barley accessions for disease reaction to barley pathogens prevalent in Canada indicated that this germplasm is a good source of resistance to Septoria passerinii, Rhynchosporium secalis and the spot-form of Pyrenophora teres, but not to Cochliobolus sativus (spot blotch phase), Puccinia graminis tritici, Ustilago nuda or barley stripe mosaic virus. A small number of accessions with resistance to the net-form of P. teres were identified. Key words:Hordeum vulgare, barley, disease resistance, net blotch, scald, speckled leaf blotch

Components of resistance in barley to stem rust: receptivity, urediniospore production, latent period, and infection response in adult plants

Resistance in barley (Hordeum vulgare) to stem rust, caused by Puccinia graminis f.sp. tritici, is often variably expressed. This study was undertaken to evaluate several components of stem rust resistance in the barley cultivars or lines Tupper, Robust, Q21861, SB90585, SB91702, and Harrington and to compare them with the susceptible wheat cultivar Little Club (Triticum aestivum). Stems of adult plants were quantitatively inoculated with urediniospores of races QCC, QFC, and TPM of P. graminis tritici. Significant differences in receptivity, urediniospore production, and latent period were observed among the barley lines and between all barley lines and Little Club wheat. The degrees of receptivity and the levels of urediniospore production on the barley lines were related to the presence or absence of the specific resistance genes Rpg1, rpg4, and possibly additional noncharacterized gene(s). Receptivity was the most strongly expressed of all of the components measured. Receptivity, spore production, and infection response were highly correlated to each other, but only infection response was significantly correlated to latent period. The usefulness of measuring these components to evaluate resistance in barley breeding is discussed. Keywords: barley, Hordeum vulgare, stem rust, Puccinia graminis tritici, resistance, components.

The transfer of stem rust resistance from the Ethiopian durum wheat St. 464 to common wheat

Two genes for stem rust (Puccinia graminis Pers. f. sp. tritici Eriks. & Henn.) resistance were transferred from the Ethiopian durum wheat (Triticum turgidum L) accession St. 464 to Thatcher and Prelude/8* Marquis common wheat. One gene was shown by monosomic analysis to be on chromosome 4B and proved to be Sr7a. Monosomic analysis failed to locate the second gene. It is only partially dominant and conditions resistance to a range of races. Key words: Rust resistance, stem rust, wheat, Puccinia graminis tritici, Triticum aestivum, Triticum turgidum

Comportamento agronômico e avaliação tecnológica dos cultivares de trigo IAC 120 (Curumi), IAC 286 (Takaoka) e IAC 289 (Marruá) para o estado de São Paulo

Avaliaram-se os cultivares de trigo IAC 120 (Curumi), IAC 286 (Takaoka) e IAC 289 (Marruá) quanto à produtividade, às reações aos agentes causais das ferrugens do colmo e da folha (em condição de campo e de casa de vegetação) e à helmintosporiose, em experimentos instalados em solos corrigidos e não corrigidos em relação à acidez, em condição de sequeiro ou de irrigação por aspersão, em diferentes regiões paulistas em 1988-92. Avaliaram-se também os cultivares por testes de tolerância a ferro, alumínio e manganês, empregando-se soluções nutritivas, em laboratório, além das qualidades físicas de panificação das farinhas obtidas dos seus grãos e o teste final de panificação. A produtividade de grãos do IAC 120 superou a do BH 1146 e do IAC 24 (controle) em 19 e 14% respectivamente, nas condições de sequeiro. O IAC 289, nas mesmas condições de cultivo, apresentou produção de grãos 26 e 19% maior em relação às testemunhas Anahuac e IAC 24 e, em condição de irrigação, foi superior 13 e 9% em relação aos mesmos controles. O IAC 286 produziu 12 e 15% a mais que o Anahuac e o IAC 24 em condições de irrigação. Para a ferrugem do colmo (Puccinia graminis tritici), em casa de vegetação, o IAC 120 demonstrou suscetibilidade às raças G11, G19, G20 e G21; o IAC 286 apresentou resistência somente às raças G11 e G17; o BH 1146 mostrou-se sensível e o IAC 289 e o Anahuac, resistentes, a todas as raças testadas. Os testes para reação à ferrugem da folha (Puccinia recondita) em casa de vegetação demonstraram que os cultivares IAC 120, IAC 286, IAC 289, BH 1146 e Anahuac foram suscetíveis a essa doença, resultados esses confirmados nos testes de campo. Todos os cultivares em estudo se apresentaram sensíveis ao agente causal da helmintosporiose, com exceção do IAC 120, que revelou resistência maior em relação aos demais; o IAC 120 mostrou-se tolerante a Al3+ e Mn 2+ e sensível a Fe 2+; o IAC 286 foi tolerante a altas doses de Al3+ e sensível a Mn2+ e Fe 2+; o IAC 289 demonstrou-se tolerante a Fe 2+ e Mn2+, e sensível a Al3+. Nos testes de panificação, os novos cultivares revelaram qualidade satisfatória: o IAC 120 apresentou farinha de glúten médio a forte, e o IAC 286 e IAC 289, farinha de glúten médio.

Windborne spread of ergot disease (Claviceps africana) in sorghum A‐lines in Zimbabwe

Ergot disease spread rapidly in Zimbabwe amongst replicated plots of male‐sterile sorghum A‐lines, from a group of centrally situated and precociously inoculated plants. Prominent secondary conidiation by the pathogen, Claviceps africana, on the surface of exuded honeydew provided airborne spores which were trapped in a Burkard continuous spore trap and showed diurnal peaks of concentration in air close to the primary source of inoculum. The rate of disease spread (r=0·2; range 0·14–0·58) closely matched that recorded for other plant pathogens such as Phytophthora infestans and Puccinia graminis tritici, and it is concluded that the characteristic secondary conidia of C. africana were the principal epidemiological agents within the experimental area. Ergot spread by windborne secondary conidia has significant epidemiological and economic implications for sorghum hybrid breeding in southern Africa.

Resistance of wild emmer wheat to stem rust: Ecological, pathological and allozyme associations

Seedling resistance to wheat stem rust was determined in populations of wild emmer wheat, Triticum dicoccoides, and characterized by means of ecological factors and allozyme genotypes. Reactions to wheat stem rust were studied in 102 single plant accessions of T. dicoccoides from ten populations by inoculation with Puccinia graminis tritici race 14, isolate GSR-739. Six populations displayed different degrees of response polymorphism with reactions ranging from high resistance to complete susceptibility, whereas four populations contained only susceptible plants. In some of the accession, unexplained intrasib variation in resistance and intraplant variation of infection-types were found. Resistance to stem rust was negatively correlated with two ecological factors, altitude and number of ‘Sharav’ (hot-dry) days which are unfavorable to disease development. Variation in stem rust response was shown to exist in ecogeographic regions where climatic variables enhanced the development of the fungus, conceivably maintained by natural selection. Likewise, allozyme genotypes, single or in multiple loci combinations, appeared to be associated with resistance or susceptibility to rust. Such association need to be verified by genetic studies in order to become established as useful markers.

Microwave fixation of rust-infected wheat leaves

Wheat leaves infected with stem rust (Puccinia graminis tritici) were infiltrated with fixative, subjected to microwave irradiation, and sliced with a vibratome. The slices were probed with antibodies, lectins, or neoglycoproteins, and processed for electron microscopy, In tissue irradiated for 10 sec to 40°C, 45°C, or 50°C, the quality of structural preservation was indistinguishable from that in control tissue subjected to conventional fixation (3 h in fixative at room temperature). The best preservation of fungal antigenic cell surface material was achieved with 10 sec of microwave-induced heating to 45°C in the presence of fixative, followed by 10 min in fixative at room temperature. Under these conditions, twice as many antigenic sites were detected on the fungal surface than in non-irradiated (“power-off” control, or conventionally-fixed) tissue. The microwave fixation protocol with heating to 45°C was used in experiments to probe infected tissue with lectins or neoglycoproteins. Most of these probes had been labelled with biotin, and this label was detected with goat anti-biotin IgG and rabbit anti-goat IgG/gold. The gold markers were localized mainly at some distance outside the outer wall layer of hyphal cells, indirectly confirming the presence of unstained extramural material that had been detected in earlier work in freeze-substituted specimens. Of seven lectins, all with demonstrated ability to bind to cross sections of intercellular hyphal walls, only concanavalin A and wheat germ lectin bound to the fungal surface. Of four neoglycoproteins, α-D-glucosyland α-D-mannosyl-BSA bound to this surface, but only the binding of the glucosyl conjugate was inhibitable with hapten. We concluded that the surface composition of these cells is less complex than previously suggested from studies using post-embedding cytochemistry.

A test of supposed mutants for stem rust resistance in wheat

Eight stem rust (Puccinia graminis tritici Eriks. and Henn.) resistant lines (designated TICENA lines) that had been selected by Veiga et al. (1981) following gamma radiation of BH-1146 wheat (Triticum aestivum L.) were studied. Six of the lines were resistant to race 15B-1 of stem rust and susceptible to race 56, and proved to carry the gene Sr7a. TICENA 4 carries two unidentified genes, each giving resistance to one of the two races. TICENA 10 carries Sr6, Sr7a and an unidentified gene giving resistance to race 56 but not 15B-1. The results raise doubts about the supposed origin of the lines as mutants.

The mode of inheritance of a type of dwarfism in common wheat

A type of dwarfism found in crosses involving the wheat (Triticum aestivum L.) cultivar Webster and a stem rust (Puccinia graminis tritici Erik. &Henn.) susceptible line, LMPG, proved to be due to a dominant gene from cv. Webster and a recessive gene from LMPG. The dominant gene is closely linked to the gene Sr30, which conditions stem rust resistance in cv. Webster and is on chromosome 5D. The dwarf plants have short, dark green, stiff leaves and rarely develop more than two leaves before dying.Key words: dwarfism, Triticum aestivum, Puccinia graminis tritici, stem rust.