A New Pathotype of Puccinia striiformis f. sp. tritici on Wheat in South Africa

Following the detection of Puccinia striiformis f. sp. tritici for the first time on wheat (Triticum aestivum) in the Western Cape in August 1996, stripe rust has spread to all the important wheat production areas in South Africa. Only the introduced pathotype (pt. 6E16) was detected in surveys of these areas during 1996 and 1997. In 1998, a severe stripe rust epidemic occurred in the eastern Free State on the extensively grown cultivars Hugenoot and Carina, both which are resistant to pt. 6E16. Stripe rust severities of 100% were common on flag and lower leaves, and widespread applications of fungicides were necessary. Avirulence/virulence characteristics of P. striifomis f. sp. tritici isolates collected from Hugenoot and Carina were determined on 17 standard stripe rust differential wheat lines and 11 supplementary testers. The latter testers included the wheat lines TP981 and TP1295 (supplied by R. Johnson, Cambridge, UK), both of which have a major resistance gene in common with the differentials Heines Peko, Reichersberg 42, Strubes Dickkopf, Clement, and Heines VII (1). Isolates obtained from Hugenoot and Carina differed from pt. 6E16 based on virulence to Reichersberg 42 (Yr7,25), Heines Peko (Yr2,6,25), TP981 (Yr25), and TP1295 (Yr25). The new variant, designated as 6E22, was also identified in collections from the province KwaZulu-Natal. Seedling tests with 6E16 and 6E22 have shown that Hugenoot, Carina, and Tugela-DN are the only local cultivars affected by the new pathotype. The occurrence of pt. 6E22, which appears to be a single-step adaptation from 6E16 adding virulence to Yr25, emphasizes the vulnerability of monogenic resistance to this disease. Reference: (1) R. A. McIntosh et al. Wheat Inform. Serv. 85:56, 1997.

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Establishment, Distribution, and Pathogenicity of Puccinia striiformis f. sp. tritici in South Africa

Plant Disease ◽

10.1094/pdis.2002.86.5.485 ◽

2002 ◽

Vol 86 (5) ◽

pp. 485-492 ◽

Cited By ~ 42

Author(s):

W. H. P. Boshoff ◽

Z. A. Pretorius ◽

B. D. van Niekerk

Keyword(s):

South Africa ◽

Stripe Rust ◽

Puccinia Striiformis ◽

Free State ◽

Grass Species ◽

Western Cape ◽

Eastern Cape ◽

Kwazulu Natal ◽

Rust Pathogen ◽

Eastern Free State

Stripe rust, caused by Puccinia striiformis Westend. f. sp. tritici Eriks., has become an endemic disease of wheat (Triticum aestivum L.) in South Africa since it was first observed near Moorreesburg, Western Cape during August 1996. The main objectives of this study were to monitor the occurrence, spread, and the possible development of new variants of the stripe rust pathogen and the susceptibility of grass species to the pathogen. Results of surveys conducted during 1996 to 1999 revealed that rainfed wheat produced in the Western Cape, Eastern Cape, and the eastern Free State, as well as irrigated wheat produced in KwaZulu-Natal and the Free State, are most likely to be affected by stripe rust epidemics. Pathotype 6E16A- with virulence to Yr2, Yr6, Yr7, Yr8, Yr11, Yr14, Yr17, and Yr19 and pathotype 6E22A- with added virulence to Yr25 were detected. The occurrence of pathotype 6E22A- is currently restricted to KwaZulu-Natal and the Free State. Stripe rust isolates found on Hordeum murinum L. in the Western Cape were identified as pathotype 6E16A-, and both pathotypes 6E16A- and 6E22A- were collected from Bromus catharticus Vahl (= B. unioloides H.B.K.) in the eastern Free Sate. Urediospores from infections similar to stripe rust found on the grass species Dactylis glomerata L. (Eastern Cape), Poa pratensis L. (= P. bidentata Stapf; Western Cape), and P. annua and P. triviales L. (eastern Free State) failed to infect wheat cv. Morocco seedlings in the glasshouse. The possible role of grasses in the over-summering of the stripe rust pathogen has not yet been established. Stripe rust infections, however, have been found on summer-sown wheat in the south Western Cape during 1998, volunteer wheat growing in the summer and autumn months in the eastern Free State from 1998 to 2000, and on summer-sown wheat in Lesotho.

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First Report of Puccinia striiformis f. sp. tritici on Wheat in South Africa

Plant Disease ◽

10.1094/pdis.1997.81.4.424d ◽

1997 ◽

Vol 81 (4) ◽

pp. 424-424 ◽

Cited By ~ 19

Author(s):

Z. A. Pretorius ◽

W. H. P. Boshoff ◽

G. H. J. Kema

Keyword(s):

South Africa ◽

Triticum Aestivum ◽

South African ◽

Stripe Rust ◽

Puccinia Striiformis ◽

Yellow Rust ◽

Climatic Conditions ◽

Western Cape ◽

South African Isolate ◽

Western Asia

During August 1996, stripe (yellow) rust, caused by Puccinia striiformis f. sp. tritici, was observed for the first time on bread wheat (Triticum aestivum) in the Western Cape, South Africa. Ensuing surveys during the growing season indicated that stripe rust occurred throughout most of the wheat-producing areas in the winter rainfall regions of the Northern, Western, and Eastern Cape provinces. The disease was also observed on irrigated wheat in the summer rainfall area south of Kimberley. Stripe rust was most severe in the Western Cape, where prolonged cool and wet conditions favored epidemic development and necessitated extensive and often repeated applications of triazole fungicides. Due to spike infection and destruction of foliage, significant losses in grain quantity and quality occurred in certain fields. Avirulence/virulence characteristics of 32 stripe rust isolates, collected from commercial wheat fields, trap nurseries, and triticale, were determined on 17 standard differential wheat lines and seven supplementary testers supplied by C. R. Wellings, Plant Breeding Institute, Cobbitty, Australia. All isolates were representative of one pathotype, characterized by avirulence to Chinese 166 (Yr1), Vilmorin 23 (Yr3), Moro (Yr10), Strubes Dickkopf, Suwon 92/Omar, Clement (Yr2,9), Triticum aestivum subsp. spelta var. album (Yr5), Hybrid 46 (Yr4), Reichersberg 42 (Yr7), Heines Peko (Yr2,6), Nord Desprez (Yr3), Carstens V, Spaldings Prolific, Heines VII (Yr2), Federation*4/Kavkaz (Yr9), and Avocet-S/Yr15, and by virulence to Kalyansona (Yr2), Heines Kolben (Yr2,6), Lee (Yr7), Compair (Yr8), and Federation 1221. Cultivars Trident (Yr17), Avocet-R (YrA), and Selkirk (YrSk) appeared heterogeneous for stripe rust reaction. The pathotype resembled race 6E16, previously detected in East and North Africa, the Middle East, and western Asia. Pathotype identity was confirmed at IPO-DLO, Wageningen, using one South African isolate of P. striiformis f. sp. tritici. In view of the rapid dispersal of the pathogen during 1996, susceptibility of several high-yielding cultivars, and favorable climatic conditions in many wheat-growing areas, stripe rust is considered potentially damaging to South African wheat production. Field observations and seedling tests have shown, however, that certain cultivars are resistant to the introduced pathotype. At present the genetic basis of this resistance is largely unknown.

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A Survey for ‘Candidatus Liberibacter’ Species in South Africa Confirms the Presence of Only ‘Ca. L. africanus’ in Commercial Citrus

Plant Disease ◽

10.1094/pdis-94-2-0244 ◽

2010 ◽

Vol 94 (2) ◽

pp. 244-249 ◽

Cited By ~ 19

Author(s):

G. Pietersen ◽

E. Arrebola ◽

J. H. J. Breytenbach ◽

L. Korsten ◽

H. F. le Roux ◽

...

Keyword(s):

South Africa ◽

Western Cape ◽

Chain Reaction ◽

Citrus Production ◽

Candidatus Liberibacter ◽

Citrus Orchards ◽

Polymerase Chain ◽

Serious Disease ◽

Production Areas ◽

Representative Samples

Greening disease of citrus is a serious disease known in South Africa since the late 1920s. In South Africa, it is associated with infection by ‘Candidatus Liberibacter africanus’, a heat sensitive, phloem-limited, noncultured alpha-proteobacterium. Huanglongbing (HLB), a similar, but more devastating disease that was described initially from China but which now occurs in several citrus producing countries, is associated with a different Liberibacter species, ‘Ca. L. asiaticus’. A ‘Ca. L. africanus’ subspecies, ‘Ca. L. africanus subsp. capensis’, has been found only in South Africa infecting an indigenous Rutaceous species, Calodendrum capense (Cape Chestnut), in the Western Cape in 1995. The discovery of a new Liberibacter species in Brazil, ‘Ca. L. americanus’, and the spread of ‘Ca. L. asiaticus’ to a number of additional countries over the last few years prompted us to assess whether only ‘Ca. L. africanus’ is present in commercial citrus orchards in South Africa. Samples displaying greening or similar symptoms were collected from 249 citrus trees from 57 orchards distributed throughout the greening affected citrus production areas of South Africa. Multiplex polymerase chain reaction (PCR) was performed on DNA extracts to detect the known citrus Liberibacters. Amplicons were obtained from 197 samples. None of the samples yielded a 1,027-bp amplicon indicative of ‘Ca. L. americanus’ infection. The amplicons of 84 samples were sequenced, and all were identical to the cognate ‘Ca. L. africanus’ Nelspruit sequence in GenBank. No instance of ‘Ca. L. asiaticus’ or ‘Ca. L. africanus subsp. capensis’ sequence was found. Geographically representative samples that tested negative for Liberibacter also tested negative for phytoplasmas based on real-time PCR results. Based on the results of this survey, it is concluded that to date only ‘Ca. L. africanus’ is associated with citrus greening in commercial citrus in South Africa.

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First Report of Stripe Rust caused by Puccinia striiformis f. sp. tritici on Wheat in Florida

Plant Health Progress ◽

10.1094/php-2005-0304-01-hn ◽

2005 ◽

Vol 6 (1) ◽

pp. 32 ◽

Cited By ~ 1

Author(s):

Ann R. Blount ◽

Shabbir A. Rizvi ◽

Ronald D. Barnett ◽

Xianming Chen ◽

Timothy S. Schubert ◽

...

Keyword(s):

Stripe Rust ◽

Puccinia Striiformis ◽

Wheat Stripe Rust ◽

First Report ◽

Documented Case ◽

Rust Pathogen ◽

Wheat Lines ◽

Yield Trials

The wheat stripe rust pathogen occured on several experimental wheat lines planted at Quincy, FL in early February 2003. Several experimental lines in the 2003 Advanced Wheat A, the Advanced Wheat B, and the Uniform Southern Wheat Nursery yield trials then showed traces of stripe rust on the leaves of the plants. An unusually cool and wet winter and spring encouraged a scattered outbreak of stripe rust of wheat on susceptible experimental lines of wheat. This report constitutes the first documented case of stripe rust of wheat in Florida. Accepted for publication 22 February 2005. Published 4 March 2005.

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Population genetic analyses of Phytophthora cinnamomi reveals three lineages and movement between natural vegetation and avocado orchards in South Africa

Phytopathology ◽

10.1094/phyto-10-21-0414-r ◽

2022 ◽

Author(s):

Juanita Engelbrecht ◽

Tuan A. Duong ◽

Trudy Paap ◽

Joseph Michael Hulbert ◽

Juanita Joyce Hanneman ◽

...

Keyword(s):

South Africa ◽

Genetic Diversity ◽

Phytophthora Cinnamomi ◽

Resistance Breeding ◽

Natural Vegetation ◽

Economic Losses ◽

Western Cape ◽

Natural Ecosystems ◽

Agricultural Industries ◽

Production Areas

Phytophthora cinnamomi is the causal agent of root rot, canker and dieback of thousands of plant species around the globe. This oomycete not only causes severe economic losses to forestry and agricultural industries, but also threatens the health of various plants in natural ecosystems. In this study, 380 isolates of P. cinnamomi from four avocado production areas and two regions of natural vegetation in South Africa were investigated using 15 microsatellite markers. These populations were found to have a low level of genetic diversity and consisted of isolates from three lineages. Shared genotypes were detected between isolates from avocado orchards and natural vegetation, indicating the movement of isolates between these areas. The population from the Western Cape natural vegetation had the highest genotypic diversity and unique alleles, indicating this could be the point of introduction of P. cinnamomi to South Africa. Index of association analysis suggested that five out of six populations were under linkage disequilibrium suggesting a clonal mode of reproduction whereas genotypes sampled from a recently established avocado orchard in the Western Cape were derived from a randomly recombined population. This study provided novel insights on the genetic diversity and spread of P. cinnamomi in South Africa. It also reported on the predominance of triploidy in natural occurring populations and provided evidence for recombination of P. cinnamomi for the first time. The presence of two dominant genotypes in all avocado production areas in South Africa highlight the importance of considering them in disease management and resistance breeding programmes.

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Development, Validation, and Re-selection of Wheat Lines with Pyramided Genes Yr64 and Yr15 Linked on the Short Arm of Chromosome 1B for Resistance to Stripe Rust

Plant Disease ◽

10.1094/pdis-03-18-0470-re ◽

2019 ◽

Vol 103 (1) ◽

pp. 51-58 ◽

Cited By ~ 8

Author(s):

Yanmin Qie ◽

Yan Liu ◽

Meinan Wang ◽

Xing Li ◽

Deven R. See ◽

...

Keyword(s):

Stripe Rust ◽

Puccinia Striiformis ◽

Durable Resistance ◽

Genotype Data ◽

Wheat Cultivars ◽

Wheat Line ◽

Individual Gene ◽

High Level ◽

Wheat Lines ◽

Selection Of

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most destructive diseases of wheat worldwide. The disease is most preferably managed by developing and growing cultivars with high-level, durable resistance. To achieve high-level and long-lasting resistance, we developed a wheat line, RIL-Yr64/Yr15, by pyramiding Yr64 and Yr15, both on the chromosome 1BS and providing high resistance to all tested Pst races. To validate RIL-Yr64/Yr15 possessing both genes, we crossed it to Avocet S (AvS). The F4 RILs from this cross were phenotyped with Pst races under controlled greenhouse conditions and also under natural Pst infection in the field. The population was genotyped with SSR markers previously reported to be linked to the resistance gene loci and with additional SSR and SNP-KASP markers along chromosome 1B. Both phenotype and genotype data confirmed the copresence of Yr64 and Yr15 in RIL-Yr64/Yr15, and the high-resolution linkage map dissected the chromosomal regions and traced their origins. New lines possessing these genes were selected from the F5 population of cross AvS × RIL-Yr64/Yr15 by marker-assisted selection. These lines with the two highly effective genes should be more useful than individual gene lines for developing high-level, durable resistant wheat cultivars.

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First Detection of Virulence in Puccinia striiformis f. sp. tritici in China to Resistance Genes Yr24 (=Yr26) Present in Wheat Cultivar Chuanmai 42

Plant Disease ◽

10.1094/pdis-94-9-1163c ◽

2010 ◽

Vol 94 (9) ◽

pp. 1163-1163 ◽

Cited By ~ 43

Author(s):

T. G. Liu ◽

Y. L. Peng ◽

W. Q. Chen ◽

Z. Y. Zhang

Keyword(s):

Stripe Rust ◽

Puccinia Striiformis ◽

Wheat Cultivar ◽

Triticum Aestivum L ◽

Fluorescent Light ◽

Rust Disease ◽

Crop Season ◽

Wheat Seedlings ◽

Stage 1 ◽

Wheat Lines

Stripe rust disease of wheat caused by Puccinia striiformis f. sp. tritici was observed on previously resistant bread wheat (Triticum aestivum L.) cv. Chuanmai 42 during the 2008–2009 crop season in Pi County, Sichuan Province, China. More than 10 single pustules were isolated from the diseased leaf samples collected in the field and inoculated on 7-day-old susceptible wheat seedlings cv. Mingxian 169. After 18 to 24 h of incubation at 100% relative humidity in darkness, the plants were moved into the greenhouse, maintained at 15 to 18°C, and supplemented with 10,000 lx of fluorescent light for 10 h per day. The second leaves were clipped when chlorotic spots appeared on leaves (~7 days postinoculation), and plants were covered with glass cylinders to prevent cross contamination. Urediniospores of each isolate were collected 16 days after inoculation and temporarily kept in a dryer at low temperature (3 to 4°C). The virulence spectra of the isolates were tested on Chinese differentials and wheat lines with known Yr genes at the seedling stage (1). A new Yr24 (=Yr26) virulent pathotype, different from currently known pathotypes in China, was identified. To our knowledge, this is the first detection of Yr24 virulence in Puccinia striiformis f. sp. tritici populations on Chuanmai 42. In addition, the new pathotype was also virulent to Lantian 17, Guinong 22 (Chinese differential), and 92R137 derived wheat lines Nannong 04Y10 and Nannong 05Y628, known to carry Yr24 (2,3). The avirulence/virulence formula of the new pathotype is Yr1, 3, 4, H46, 5, 6, 15, 17, 18, 32, Sp, Sd/Yr2, 8, 9, 10, 12, 24 (=26), 31, and Su. Wheat cultivars and breeding materials, previously protected by Yr24 gene, are now vulnerable to stripe rust epidemics in the region. Pure isolates of the new pathotype (Accession No. 09-6-16-3) are stored in the Chinese Academy of Agricultural Sciences (CAAS; Beijing) stripe rust collection. References: (1) W. Q. Chen et al. Plant Dis. 93:1093, 2009. (2) G. Q. Li et al. Theor. Appl. Genet. 112:1434, 2006. (3) Z. F. Li et al. Plant Dis. 90:1302, 2006.

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Seedling and Slow Rusting Resistance to Stripe Rust in Chinese Common Wheats

Plant Disease ◽

10.1094/pd-90-1302 ◽

2006 ◽

Vol 90 (10) ◽

pp. 1302-1312 ◽

Cited By ~ 38

Author(s):

Z. F. Li ◽

X. C. Xia ◽

X. C. Zhou ◽

Y. C. Niu ◽

Z. H. He ◽

...

Keyword(s):

Stripe Rust ◽

Resistance Genes ◽

Rust Resistance ◽

Puccinia Striiformis ◽

Gene Pyramiding ◽

Stripe Rust Resistance ◽

Slow Rusting ◽

Cropping Seasons ◽

Wheat Lines ◽

Rust Resistance Genes

Identification of seedling and slow stripe rust resistance genes is important for gene pyramiding, gene deployment, and developing slow-rusting wheat cultivars to control the disease. A total of 98 Chinese lines were inoculated with 26 pathotypes of Puccinia striiformis f. sp. tritici for postulation of stripe rust resistance genes effective at the seedling stage. A total of 135 wheat lines were planted at two locations to characterize their slow rusting responses to stripe rust in the 2003-2004 and 2004-2005 cropping seasons. Genes Yr2, Yr3a, Yr4a, Yr6, Yr7, Yr9, Yr26, Yr27, and YrSD, either singly or in combinations, were postulated in 72 lines, whereas known resistance genes were not identified in the other 26 accessions. The resistance genes Yr9 and Yr26 were found in 42 and 19 accessions, respectively. Yr3a and Yr4a were detected in two lines, and four lines may contain Yr6. Three lines were postulated to possess YrSD, one carried Yr27, and one may possess Yr7. Thirty-three lines showed slow stripe rusting resistance at two locations in both seasons.

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