Single Pustule Research Articles

Puccinia graminis f. sp. tritici races identified on wheat and Berberis spp. in northern Turkey

Wheat is a commonly grown crop in Turkey. Rust diseases are among the most important biotic factors affecting wheat yield and quality. Stem rust of wheat caused by Puccinia graminis f. sp. tritici is one of the oldest known diseases of wheat. Wheat stem rust is common in Kastamonu province located in the northern part of Turkey. In addition, Berberis species are also common in Kastamonu province. In this study which was conducted in 2016 and 2017 in Kastamonu province, stem rust races occurring on Berberis species and wheat plants were determined. Forty single pustule aeciospores from Berberis plants were obtained. The most common stem rust race originating from Berberis plants was TTTTF. Other stem rust races from Berberis plants were RTTTF, RTTTC, TTTTC, and TTKTF. From wheat, 74 single pustule isolates of stem rust were obtained. The most common stem rust race originating from wheat was also TTTTF. Other stem rust races from wheat plants were TTKTF, TTTTC, TTKTC, RTTTF, and RTTTC.

Distribution and Physiological Races of Wheat Stem Rust (Puccinia graminis F. Sp tritici) in North and East Shoa Zones of Ethiopia

Wheat (Triticum aestivumL.) is the most important staple crop in temperate zones and is in increasing demand in countries undergoing urbanization and industrialization. However, its production is affected by many biotic and abiotic factors. Among biotic production constraints; wheat stem rust ( Puccinia graminis f.sp tritici) is the most important one. This study was (i) to assess the importance of wheat stem rust in North and East Shoa zones of central Ethiopia and (ii) to identify physiological races. Purposive multistage sampling was used to select major wheat growing districts and farmers associations from each zone. Wheat stem rust race identification was carried out via inoculation of isolates on susceptible line (McNair); single pustule isolation; inoculation on standard differential sets and infection type evaluation of each line fourteen days after inoculation. One hundred fifty wheat fields (75 from each zone) were assessed. Wheat stem rust was observed in 71 (94.7%) and 52 (73.3%) of wheat fields in East and North Shoa zones, respectively. Disease incidence and severity were significantly different (p < 0.0001) between the two zones. Six physiological races of Puccinia graminis f.sp tritici (pgt) namely; TKTTF, TTTTF, TKKTF, TTKTT, TTKTF and TTTTT were identified. TKKTF was the dominant race which was detected from 40 (48.2%) samples followed by TKTTF (Digelu race) which was identified from 28 (33.7%) samples. But, TTTTT, TTKTT and TTTTF were less frequent races. They were identified from 1 (1.2%), 2 (2.4%) and 4 (4.8%) samples, respectively. The majority of resistance genes in differential host lines (80-100%) were defeated with the races. Resistance genes Sr24 and Sr31 were effective to majority of races identified. Hence, they can be used as source of resistance in breeding program.

Occurrence and pathogenicity of Puccinia coronata var avenae f. sp. avenae on oat in South Africa

Crown rust, caused by Puccinia coronata Corda var. avenae f. sp. avenae (Urban & Marková) (Pca), can negatively impact oat (Avena sativa L.) production in South Africa and little is known about pathogenic variability and cultivar response. Pca infected leaves were obtained from oat trial plots, commercial fields and wild oat (Avena spp.) during the 2016 and 2017 growing seasons for race analysis. Uncharacterised collections from 1998 to 2005 were also included. Single pustule isolates were derived from field collections and used for race typing on 16 international differential lines. Six races were identified from 88 isolates pathotyped with race JBLL originating from wild oat samples, SGLL, SQPL and SSTL from commercial oat samples and SBLL+ from both wild and commercial oat samples. Isolates collected in 1998 typed as races SBLL and SBLL+ and the 2005 isolates as race SQPL. Race SBLL was not detected in the 2016 and 2017 samples with SBLL+ being dominant during 2016–17. This is the first report of South African races with virulence for the resistance genes Pc38, Pc58 and Pc59. Seedling infection types of 70 additional oat lines and cultivars to the described races showed incompatible phenotypes for 27 entries. Field data revealed moderate to high levels of adult plant resistance for a few cultivars to races SBLL+ and SSTL. Genetic analysis of 31 isolates, including two USA control isolates, revealed three genetic lineages. No apparent correlation was observed among year of collection, geographic origin, phenotype and genotype of isolates except for race JBLL that originated from wild oat collections in the Western Cape.

Habilidad competitiva de razas de roya de la hoja provenientes de trigos cristalinos

En el proceso de mejoramiento genético de trigo, la evaluación de genotipos por resistencia a royas es fundamental, se tienen que mezclar distintas razas; sin embargo, es primordial conocer su habilidad competitiva y en que genotipo se deben incrementar; por lo que el objetivo del estudio fue medir la habilidad competitiva de cuatro razas de roya de la hoja causada por Puccinia triticina E. que atacan trigos cristalinos (Triticum durum). El estudio se realizó en invernadero durante el año 2015. Las razas BBG/BN, BCG/BN, BBG/BP y CBG/BP, fueron mezcladas y multiplicadas por tres generaciones sucesivas en genotipos susceptibles (Atil C2001 y Morocco), genotipos resistentes (Samayoa C2004 y Thatcher-Lr16 (RL6005)) además de Júpare C2001 resistente a BBG/BN y BCG/BN, pero susceptible a BBG/BP y CBG/BP. Después de la reproducción de urediniosporas, se obtuvieron 100 aislamientos que se incrementaron en Morocco y se procedió a la identificación. La raza identificada con más frecuencia fue CBG/BP con 46%, seguida de BBG/BP con 34% y BBG/BN con 18%, mientras que BCG/BN fue la menos frecuente con 2%. Solo en urediniosporas del compuesto masal (CM) obtenidos de RL6005 y Morocco permitió identificar las cuatro razas, en Atil C2001, Júpare C2001 y Samayoa C2004 solo se identificaron tres. La raza identificada con más frecuencia en Atil C2001, RL6005 y Samayoa C2004 fue BBG/BP, mientras que en Morocco y Júpare C2001, fue CBG/BP. Se concluye que CBG/BP es más competitiva que BBG/BP, BBG/BN y BCG/BN y se recomienda usarse en la mezcla.

Diversity of virulence phenotypes of Puccinia triticinain different agroclimatic zones of the North Caucasus

The phenotypic composition of the North Caucasian population of wheat leaf rust pathogen (Puccinia triticina Erikks.) in various agro-climatic zones of the region in 2016-2018 is analyzed. 233 single pustule isolates were studied, of which 212 virulence phenotypes were identified. In all the years of research, a high level of population diversity was established (the Shannon index (Sh) was 0.92-0.99). The dominant phenotype in 2016 was the PHRS phenotype, which was identified in the southern foothill, western Azov and eastern steppe agro-climatic zones. In the population of 2016, phenotypes with a high and medium number of virulence genes prevailed. In 2017, the most represented are the phenotypes of DCRL, LBLL (Western Azov zone) and PCQB (Northern zone). Avirulent phenotype BBBB was common for populations of 20162018. In 2016, a phenotype with virulence to Lr9 (TLGS) was first detected. In 2017 and 2018, phenotypes virulent to the Lr24 gene (PKTT, SFGQ, CFPQ, TKTS, MKTT, LKSR) were detected in the populations of the fungus. A high level of population differences in phenotypic composition between the years of research was established (Rogers index (R) was 0.96 -0.99).

Diversity in Puccinia graminis f. sp. avenae and its impact on oat cultivar response in South Africa

Puccinia graminis f. sp. avenae (Pga) samples were collected from cultivated oat (Avena sativa L.) in trial plots and commercial fields and from wild oat (Avena spp.) during the 2016 and 2017 seasons. Field samples were purified through selection of single pustule isolates and subsequent urediniospore increases using the susceptible cultivar Swan. For race phenotyping, a set of 12 international differential lines was used that resulted in the identification of races RSJ, RJS and RJJ. Race RSJ was the most prevalent (60% of isolates) followed by races RJS (34%) and RJJ (6%). These races varied in virulence for Pg6 and Pg12, with no avirulence recorded for Pg1, 2, 4, 8, 9, 13 and Pg15 and no virulence for Pg3, 10 and Pg16. Seedling infection types of 32 oat cultivars to the three described races showed compatible phenotypes for all cultivars towards at least one of the races. Moderate levels of adult plant resistance against races RJS and RSJ were recorded for seven cultivars during field tests in 2017 and 2018. Thirteen microsatellite markers used to assess genetic variability amongst twenty four field isolates revealed three sub-populations of which only one correlated with the race phenotype. The results contributed to our understanding of the diversity of the Pga population in South Africa, including useful resistance sources and cultivar responses.

Additive Manufacturing of Devices Used for Collection and Application of Cereal Rust Urediniospores.

Optimized inoculation procedures are an important consideration in achieving repeatable plant infection when working with biotrophic rust fungi. Several plant pathology laboratories specializing in rust research employ a system where the collection and application of fungal spores are accomplished using an exchangeable gelatin capsule. Urediniospores are collected from erumpent pustules on plant surfaces into a capsule fitted to a cyclone collector controlled by a vacuum pump. By adding light mineral oil to the same capsule, the spore suspension is then sprayed onto plants by means of a dedicated atomizer (inoculator) connected to an air pressure source. Although devices are not commercially available, modern day technologies provide an opportunity to efficiently design and manufacture collectors and inoculators. Using a process called Additive Manufacturing (AM), also known as “3D printing,” the bodies of a collector and inoculator were digitally designed and then laser-sintered in nylon. Depending on availability, copper or aluminum tubes were fitted to the bodies of both devices afterward to either facilitate directed collection of spores from rust pustules on plant surfaces or act as a siphon tube to deliver the spore suspension contained in the capsule. No statistical differences were found between AM and metal inoculators for spray delivery time or spore deposition per unit area. In replicated collection and inoculation tests of wheat seedlings with urediniospore bulks or single pustule collections of Puccinia triticina and P. graminis f. sp. tritici, the causal organisms of leaf rust and stem rust, consistent and satisfactory infection levels were achieved. Immersing used devices in acetone for 60 s followed by a 2 h heat treatment at 75°C produced no contaminant infection in follow-up tests.

ВИРУЛЕНТНОСТЬ ПОПУЛЯЦИЙ PUCCINIA TRITICINA ERIKSS. В НЕЧЕРНОЗЕМНОЙ ПОЛОСЕ РОССИИ

As a result of surveys of wheat crops in the Moscow region in 2009-2017 there were collected 27 wheat samples leaf rust infected. Isolates from single pustule were studied by the standard method. To study the frame of leaf rust population there was used a set of 42 Lr-lines monogenic of cv. Thatcher. For the period from 2009 to 2017 there were studied for virulence 120 isolates of P. triticina. Isolates differed significantly in virulence. By virulence formulas all leaf rust isolates were attributed to 103 phenotypes, differing by one or two or several genes. During all the years of testing the population of P. triticina was showed high virulence affecting from 30 to 34 Lr-lines of wheat. Annually in the population of P. triticina there were found out 18 virulence genes with a high frequency (average 78.0-98.9%): p1, p2c, p3a, p3b, p3ka, p10, p14a, p14b, p17, p18, p21, p27 + p31, p30, p32, p33, p39, p40, pB, and 7 genes were never met: p24, p29, p41, p42, p47, p51, p53. The genes p2a, p2b, p11, p15, p20, p23, p25, p26, p46 were constantly detected in the fungus population, but their frequency varied greatly over the years (on average, from 34.5 to 72.0%). As for the genes p9, p16, p19, p28, p36, p38, p44, p45, they there were not found every year in the population of P. triticina. Depending on the stability of the isogenic Lr-line of wheat, the type reactions to disease development were differed: from high susceptibility to immunity. By the number of virulent isolates of the fungus to wheat Lr-lines there were determined the degree of effectiveness of resistance genes. Lr-genes so as Lr24, Lr29, Lr41, Lr42, Lr47, Lr51, Lr53 were effective to leaf rust. They can be recommended for breeders as donors of resistance to leaf rust.

Physiological specialization of Puccinia triticina, the causal agent of wheat leaf rust, in Canada in 2012

Two hundred and thirty-three single pustule isolates of Puccinia triticina were recovered from leaf rust infected wheat leaves from across Canada in 2012. These were tested for virulence on 16 standard differential lines and two additional lines containing Lr21 and LrCen, respectively. There were 49 different virulence phenotypes found, the most common of which were TBBG (18.9%), TNBG (15.0%), TDBJ (7.7%) and MBDS (6.4%). From Manitoba and Saskatchewan, 28 virulence phenotypes were found among 177 isolates, with the most common being TBBG (22.0%), TNBG (18.6%), TDBJ (10.2%) and MBDS (7.3%). There were 13 virulence phenotypes among 22 isolates from Ontario – MBTN (34.8%), MCGJ and TDPN (9.1% each) were the most common. Thirteen virulence phenotypes were found from 20 isolates in Quebec, with TBBG (25%), TNBG, MBDS, MBTN (each at 10.0%) being the most frequent. Two virulence phenotypes were found from among 14 isolates from Prince Edward Island, 12 isolates were TBRK, and two were TBRJ. There were some changes in virulence frequencies in 2012 compared with 2011, including increases for Lr2a, Lr2c, Lr9, Lr18 and Lr21, while there were decreases to Lr24, Lr26, Lr3ka, Lr17, LrB and Lr14a. Virulence to Lr21 was first found at 5.2% in Canada in 2011, and this increased to 7.7% in 2012. Since many Canadian wheat cultivars have Lr21, this could lead to greater susceptibility to leaf rust. However, all the Lr21 virulent isolates were found only in western Canada and in just four virulence phenotypes.

Phenotypic and genotypic description of Puccinia graminis f. sp. tritici race 2SA55 in South Africa

Race 2SA55 of the wheat stem rust pathogen, Puccinia graminis f. sp. tritici, was described for the first time during 2000 in South Africa. This race is of particular interest as it was the first local report of increased virulence towards barley cultivars by wheat stem rust. Using three original accessions of 2SA55 from the rust collection of the University of the Free State, nine single pustule isolates were established. Phenotyping of isolates to characterise 2SA55 according to the North American nomenclature system revealed variation in virulence for Sr9g on the tester lines Kubanka and Acme, which was not detected in the initial description of 2SA55. Seven isolates coded as BNGSC, which except for virulence on Sr9b resembled the initial avirulence/virulence description for 2SA55. The remaining two isolates with Sr9g virulence coded as BPGSC. The seedling infection types for the two 2SA55 derived races BNGSC and BPGSC on the Stakman differential set as well as on an extended set of Sr lines and 144 South African wheat cultivars and advanced breeding lines revealed no further distinction in reaction between them. Microsatellite analysis indicated that while race BN/PGSC shares phenotypic similarity with several of the South African non-Ug99 races, it was genetically distinct.

Characteristics of virulence of Puccinia triticina populations and the potential of the Lr24, Lr25, LrSp genes for spring common wheat breeding in the Southern Ural

Monitoring of pathogen populations is important for successful genetic wheat protection against leaf rust and identification of pathotypes with virulence to the resistance genes used. The aim of this work was analysis of Puccinia triticina populations in the Chelyabinsk region for virulence and studying the effectiveness of Lr-genes at the field for improving and stabilization of genetic protection from wheat leaf rust in the Southern Urals. Infection materials were collected in the experimental field of the Сhelyabinsk Research Institute of Agriculture from breeding lines, commercial and perspective wheat varieties in 2014–2016. In total, 383 single pustule isolates were studied: 180 in 2014, 131 in 2015, and 72 in 2016. The Lr24 gene was characterized as highly effective. The single isolate virulent to ТсLr19 line was revealed only in 2014. Isolates virulent to the Lr9 gene occurred annually both on the varieties carrying this gene and those without it, and all of them were characterized by avirulence to the Lr26 gene. According to the Nei index (N), no significant differences in virulence were revealed between Chelyabinsk populations in 2014–2016. 27 virulence phenotypes were determined using 20 TcLr-lines. The phenotypes TQTTR and TGTTR avirulent to lines ТсLr19, ТсLr24, ТсLr26 and ТсLr9, ТсLr19, ТсLr24, ТсLr26, respectively, were common in 2014–2016. The results on the effectiveness of Lr-genes at the seedling stage correlated with estimates for Thatcher Lr-lines, breeding materials and varieties with known Lr-genes grown at the field on the breeding nursery of the Сhelyabinsk Research Institute of Agriculture. The highly effective genes Lr24, Lr25, Lr28, Lr29, Lr37 and some others were found to have promise for use in wheat breeding in the Ural. The use of these genes and combination of these genes with non-effective ones will allow the genetic diversity of new wheat varieties to be increased and the fungus populations to be stabilized. By now, at the field conditions in the Ural region, the effective combinations of Lr-genes revealed are Lr9+Lr19, Lr9+Lr26, Lr9+Lr37, Lr9+Lr10+Lr26, and Lr9+Lr26+Lr37.

Physiologic specialization of Puccinia triticina, the causal agent of wheat leaf rust, in Canada in 2010

Puccinia triticina Eriks., the causal agent of wheat leaf rust, was collected across Canada in 2010 to determine the virulence spectrum present in the pathogen population. From 314 infected leaf collections, 399 single pustule isolates were recovered, including 341 from Manitoba and Saskatchewan, 38 from Ontario, nine from Quebec and 11 from Prince Edward Island (PEI). When analysed for virulence on 16 standard differential lines, 41 different virulence phenotypes were identified. The most common were MLDS (26.1%), TDBJ (22.8%) and TDBG (11.8%). In Manitoba and Saskatchewan, the most common phenotypes were MLDS (29.6%), TDBJ (25.5%) and TDBG (13.8%), which were also abundant in 2009. In Ontario, the most common were MBTN (23.7%), TDBJ (10.5%), MCGJ, MCTN and MLDS (each at 7.9%), whereas in Quebec, each of the nine isolates analysed had a different phenotype. In PEI, the more commonly isolated phenotypes were MBNQ (six isolates), MBTN and MHNQ (two isolates each). Each population had unique virulence phenotypes, and the eastern populations were more diverse than the Manitoba and Saskatchewan population. Virulence trends from previous years continued in 2010, with increasing levels of virulence found for Lr9 and Lr17 while decreasing virulence was found for Lr2a, Lr14a and Lr24. There was no virulence found in 2010 for Lr19, Lr21, Lr22a, Lr29, Lr32 or Lr52.

Short communication: Emergence of a new race of leaf rust with combined virulence to Lr14a and Lr72 genes on durum wheat

Leaf rust is a foliar disease caused by the fungus Puccinia triticina that may severely reduce durum wheat yield. Resistance to this pathogen is common in modern durum germplasm but is frequently based on Lr72 and Lr14a. After accounts of races with virulence to Lr14a gene in France in 2000, the present study reports the detection in 2013 for the first time of a new race with virulence to Lr14a and Lr72. The aim of this work was to characterize the virulence pattern of four Spanish isolates with virulence to Lr14a, and to discuss the consequences of this presence. Rusted leaves from cultivars ‘Don Jaime’ (Lr14a) and ‘Gallareta’ (Lr72) were collected in 2013 in the field at two Spanish sites, one in the south (near Cadiz) and another in the north (near Girona). Spores from single pustule for each cultivar and site were multiplied on susceptible cultivar ‘Don Rafael’. Then, the four isolates were inoculated on a set of 19 isogenic lines Thatcher to characterize their virulence spectrum. All isolates presented the same virulence pattern. They were virulent on both Lr14a and Lr72 and the race was named DBB/BS. This race was very similar to those reported in 2009-11, but with added virulence to Lr14a. The resistance based on Lr14a has therefore been overcome in Spain, by a new race that has likely emerged via stepwise mutation from the local predominating races. This information is important to guide breeders in their breeding programmes and gene deployment strategies.

Virulence Analysis of Wheat Powdery Mildew (Blumeria graminis f. sp. tritici) and Effective Genes in Middle Delta, Egypt.

Wheat powdery mildew (Blumeria graminis f. sp. tritici) has increased in Delta Egypt in recent years as a result of growing susceptible cultivars of bread wheat. Fifty-two isolates of B. graminis f. sp. tritici collected in 2013 and 2014 from commercial fields in five provinces were analyzed for virulence, using 21 genes conferring resistance to powdery mildew (Pm genes) as well as 12 local wheat cultivars. First true leaves of 10-day-old wheat differentials were inoculated with isolates derived from a single pustule of B. graminis f. sp. tritici. No virulence to the resistance genes Pm3d, Pm12, Pm16, Pm24, Pm35, Pm36, and Pm37 was detected, indicating that these genes could be used for resistance breeding. Virulence to Pm2, Pm4a, and Pm6 was low, while high virulence to genes Pm1a, Pm3a, Pm3c, Pm3f, Pm5a, Pm7, Pm8, Pm9, and Pm17 was found, indicating that breeders should be very cautious in using these genes. At the adult stage, genes Pm2, Pm3d, Pm3f, Pm4a, Pm6, Pm12, Pm16, Pm17, Pm24, Pm35, Pm36, and Pm37 were completely effective in both years. All the tested Egyptian wheat cultivars were susceptible under natural field conditions. The virulence of B. graminis f. sp. tritici population and resistance Pm genes have been assessed for the first time in Egypt.

Virulent Race Overcome Wheat Stem Rust Resistance Gene Sr27 in Egypt

Triticale is an excellent source of resistance to wheat stem rust, caused by Puccinia graminis f.sp. tritici. Stem rust historically is one of the most destructive diseases of wheat (Triticum aestivum L.) worldwide. Deployment of resistant genotypes successfully prevented rust epidemics over the past several decades. This is primarily due to the on-going incorporation of effective stem rust resistance genes into new wheat breeding materials; this may place the pathogen under great selection pressure. Although Sr27 has little effect on the commercial wheat production, it has a major impact on the commercial triticale cultivars. In Egypt, high levels of stem rust infection were observed on wheat cultivar (Cooring) which carrying Sr27 grown at Gemmiza Research Station during May 2015. Samples collected from rusted stems of wheat cultivar (Cooring) were cut and artificially inoculated on primary leaves of 8-day-old seedlings of highly susceptible wheat Cv. Morocco. Four single pustules were collected and race analysis was done. Results showed that out of the four identified races, race QQQCM was the most virulent one wheat seedling carrying Sr27 with infection type (4), whereas the rest of races were a virulent to Sr27. This race (QQQCM) first time toappear in Egypt from previous identified races. Regarding to the performance of 20 stem rust resistant genes at seedling stage, (Sr 9e,7b,8a,9g,30,17,9a,9d,10,31and Sr38) were resistant to race QQQCM, meanwhile the rest Srs were susceptible

Physiologic specialization of Puccinia triticina in Syria

Leaf rust, caused by Puccinia triticina Eriks., is one of the major diseases of wheat in Syria. Surveys of durum wheat fields were carried out in all durum wheat growing regions in Syria during 2010. A total of 120 samples of P. triticina were collected. Single pustules from each collection were multiplied on the susceptible cultivar Cham1. Eighty-five percent of the surveyed fields were infested with wheat leaf rust, the greatest rate recorded in Syria during the previous seven growing seasons (2003–09). Twenty physiologc races were identified using the North American system of nomenclature, and six groups of races were identified using the Unified System. Races varied in their frequency and virulence. Four races were recorded for the first time in Syria, including LBBT, PMRR, SCBK and TBRM. The most virulent races found in the study were TBRT, first recorded in Lebanon in 2008, and PMRR, followed by PBPT, TBLR, TBRM, TLRB, CBRT, and SBRN. Some of the older races, such as CBRT which was first found in 2005 only in a few fields in Latakia in Western Syria, were found in most regions sampled. The host resistance gene Lr24 was completely effective against all twenty physiologic races identified. This gene is recommended for use by wheat breeders to improve the resistance for leaf rust in new wheat cultivars.

Virulence Spectrum of Puccinia hordei of Barley in Western and Central Highlands of Ethiopia

Virulence surveys of Puccinia hordei of barley were conducted in the main and off crop seasons of 2010/11 and 2011/12 in West Shewa, Wellega (western part of the country) and Arsi (central part of the country) zones of Oromiya region, Ethiopia to determine the virulence spectrum of the pathogen, and identify the effective resistance genes to the pathotypes. In the two crop seasons, 56 leaf (brown) rust samples in the main and 32 in the offseason were collected. From each barley field, single pustule descent spores were multiplied and inoculated onto the seedlings of 12 leaf rust differentials carrying Rph1 - Rph12 genes to designate the pathotypes. A total of 88 leaf rust isolates were processed and based on infection phenotype on the resistance genes, 7 pathotypes (ETPh6631, ETPh6611, ETPh6671, ETPh7671, ETPh7631, ETPh7611 and ETPh7651) were identified. The most frequently isolated pathotype was ETPh6631 with 43.2% followed by ETPh6611 with 19%. Moreover, virulence spectrum of P. hordei pathotypes identified in this study was diverse. Resistance genes with Rph1 (Sudan), Rph4 (Gold), Rph8 (Egypt4), Rph9 (Hor 2596), Rph11 (Clipper BC68) and Rph12 (Triumph) were non-effective to all pathotypes identified whereas genes Rph5 (Magnif), Rph6 (Bolivia) and Rph10 (Clipper BC 8) were effective to 26.1, 73.9 and 78.4% of the isolates, respectively. Virulence against Rph2 (Peruvian), Rph3 (Estate) and Rph7 (Cebada Capa) was absent. Therefore, the effective major genes to the existing leaf rust populations could be utilized as sources of resistance in the barley breeding program.

First Report of Rust Caused by Puccinia psidii on Eucalyptus dunnii in Uruguay.

Eucalypt rust caused by Puccinia psidii Winter represents a major disease affecting eucalypt production in South America, and is threatening myrtaceous hosts worldwide. In Uruguay, it was first detected infecting Eucalyptus globulus in 2001 (4) and later on E. grandis, Myrrhinium atropurpureum, and Myrcianthes pungens, two myrtaceae hosts native to Uruguay (3). Over the summer 2013, bright orange-yellowish pustules were detected on stock plants of E. dunnii in a nursery located in western Uruguay, province of Paysandú. A severe and explosive epidemic was readily observed. Affected leaves were taken to the laboratory and examined under the microscope. Uredinia and urediniospores were similar with those described previously in Uruguay on other hosts (3,4). Uredioniospores were 18 to 25 × 15 to 21 μm, yellow, unicellular, spherical to elliptical, base truncate, finely and uniformly echinulate with spines up to 1 μm long, with an evident bald patch without spines. To confirm identity of this fungus, genomic DNA was extracted from single-pustule urediniospores, and ITS region was amplified using primers PR1 and PR2 (1) with PCR conditions previously described (3). Forward and reverse sequences from three single pustules were obtained, assembled, and compared with those available in GenBank using BLAST searches. Obtained sequences showed to be identical to those analyzed by Pérez et al. (2011) collected from E. grandis and E. globulus, with no variation found in the analyzed region. A 100% identity was found with isolates UY1374 and UY1375 obtained from E. globulus, and with isolate UY1731 obtained from E. grandis (FJ710805, FJ710806, and FJ710807, respectively). Sequences were deposited in GenBank with accession numbers KM083129, KM083130, and KM083131. Even though this pathogen is known to occur in a wide variety of myrtaceous species, to our knowledge, this is the first natural infection record of P. psidii on E. dunnii in Uruguay and worldwide. This report confirms previous studies that indicated the susceptibility of E. dunnii when inoculated under controlled conditions (2,5). E. dunnii is being widely planted in Uruguay, eastern Argentina, and southern Brazil, with increasing significance to the pulp industry. Although the consequences of this finding have yet to be realized, scouting plantations is essential to estimate the real impact of this pathogen on this tree species. Our study contributes to expand the host range known for this globally important pathogen.

First Report of Puccinia triticina (Leaf Rust) Race FBPT on Wheat in South Africa

Eleven isolates of Puccinia triticina Erikss. collected from bread wheat (Triticum aestivum L.) in the Western Cape during the 2010 annual rust survey were pathotyped to a race not previously recorded in South Africa. Replicated race analysis on seedlings of 16 Thatcher (Tc) near-isogenic differential lines at two rust laboratories confirmed avirulence (infection types [ITs] 0; to 2+) for lines with Lr1, Lr2a, Lr9, Lr11, Lr16, Lr24, and Lr26 and virulence (ITs 3 to 4) for lines with Lr2c, Lr3, Lr3ka, Lr10, Lr14a, Lr17, Lr18, Lr30, and LrB. Thatcher lines with LrB, Lr10, Lr14a, and Lr18 were added as the fourth set to the 12 original differential lines (1,2). This profile codes to race FBPT according to the North American system, and, based on these differentials, resembles a P. triticina isolate from Gwebi, Zimbabwe, in 2012 (Z. A. Pretorius, unpublished data). When additional single gene lines were tested with FBPT (race 3SA147 according to the ARC-Small Grain Institute rust notation procedure), lines with Lr2b, Lr15, Lr19, Lr20, Lr21, Lr25, Lr27+31, Lr28, Lr29, Lr32, Lr36, Lr38, Lr45, Lr47, Lr50, Lr51, and Lr52 were effective, whereas lines with Lr3bg, Lr23, Lr28, and Lr33 were ineffective. In adult plant tests in a greenhouse, Thatcher lines containing Lr12 (IT ;1c), Lr13 (IT ;1c), Lr22a (IT 1), Lr35 (IT ;1+), and Lr37 (IT ;1) were resistant, whereas Thatcher (Lr22b) was susceptible. Of 146 South African cultivars and lines infected as seedlings with 3SA147 (FBPT), 83% were resistant (IT ≤ 2) and 5% showed within-line variation. Entries showing compatible ITs with 3SA147 (FBPT) were also susceptible to either or both of 3SA133 (PDRS) and 3SA146 (MCDS). In addition, the new race was genotyped using 16 simple sequence repeat (SSR) primer-combinations (3). Three single pustule isolates of 3SA147 (FBPT) were identical and showed 82% and 76% similarity with the recently described races 3SA146 (MCDS) and 3SA145 (CCPS), respectively (4). Minimum spanning network analysis confirmed this close genetic relationship among the three races. However, since their virulence phenotypes differ, it is proposed that 3SA147 (FBPT) is not a stepwise mutation from either 3SA145 (CCPS) or 3SA146 (MCDS), but rather a foreign introduction into South Africa. As most current breeding lines and wheat cultivars are resistant, it is unlikely that race FBPT will threaten wheat production in South Africa, but its detection underlines the fact that new P. triticina variants have been occurring at regular intervals in the region.

English

&nbsp; Bean rust (Uromyces appendiculatus&nbsp;(Pers.:Pers.) Unger var.&nbsp;appendiculatus) is one of the most devastating and variable pathogens of common bean (Phaseolus vulgaris&nbsp;L.) worldwide that can cause total crop loss. Characterization of bean rust races can help in screening resistant materials during gene pyramiding. The aims of the present research were first, to characterize bean rust isolates collected from snap bean growing areas in Kenya. Secondly, to identify which of the available rust resistance genes in common bean differentials are most effective to control rust in those areas. Snap bean leaf tissues with rust pustules were collected from different farms in eight locations in central and western Kenya during the years 2010 and 2011. Forty seven single pustule isolates were obtained and inoculated on 12 bean rust differential cultivars. For consistent results, the inoculation was repeated twice. The new international classification system and the binary nomenclature grouped the 47 single pustule isolates of&nbsp;U. appendiculatus&nbsp;into 9 different races, most of this affected the Andean gene pool. Hierarchical cluster analysis grouped the races into two major clusters depending on the virulence of the races on the host differential cultivars. The most resistant genes for pyramiding in Kenya were identified as&nbsp;Ur-5,&nbsp;Ur-11&nbsp;and&nbsp;Ur-CNC. An important output of this study was the identification of races with potential use during gene pyramiding process. &nbsp; Key words:&nbsp;Uromyces appendiculatus, snap bean, races, genes, characterization.