All BGRI Abstracts

Displaying 411 - 415 of 415 records | 42 of 42 pages

Wheat rust status and its implications in Pakistan

Mirza Crop Diseases Research Institute, Pakistan Agricultural Research Council, Pakistan

Detailed rust surveillance of wheat growing areas in Pakistan was conducted from 2011 to 2014. Information about varietal distribution, growth stage, and rust incidence and severity was collected at 950 locations, and rust samples collected from these locations were subjected to race analysis. Yellow rust showed increasing incidence of high to moderate severity. Commercial cultivars released during 1991 to 2011 showed MS to S reactions. Twenty eight races were identified, most with wide virulence ranges. The frequencies of virulence to Yr1, Yr6, Yr7, Yr8, Yr9, Yr17, Yr27, Yr43, Yr44 and YrExp2 all exceeded 50%. Leaf rust also showed increasing incidence, mainly due to cultivation of the susceptible cv. Sehr-06. Fourteen races were identified. The frequencies of virulence to Lr1, Lr2c, Lr3a, Lr16, Lr26, Lr3c, Lr17a, Lr30, LrB, Lr10, Lr14a, Lr14b and Lr21 exceeded 50%. Virulences to Lr2, Lr9, Lr24, Lr18 and Lr19 were not detected and frequencies of virulence to Lr11 and Lr20 were low. Current and old commercial cultivars showed MS to S reactions. In 2011 and 2014 stem rust incidence was sporadic, but in 2013 it was present at 33 of 232 locations in Sindh, Punjab, Khyber Pakhtunkhwa and Baluchistan. Race RRTTF was identified in all samples.

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Genomic selection for wheat traits and trait stability

Huang Horticulture and Crop Science, the Ohio State University, Ohio Agricultural Research and Development Center, USA

Trait and trait stability are important for wheat breeding. Our objectives were to assess the relative efficiency of genomic selection (GS) for various wheat traits and trait stability using four different models. Genotyping was conducted with a 90K SNP chip panel. SNP tagging was used to obtain a subset of 3,919 relatively independent markers for downstream analysis. Phenotyping was conducted on a population consisting of 273 lines, from seven different soft red winter wheat breeding programs in the U.S.A. Eberhart and Russells’ regression and additive main effects and multiplicative interaction (AMMI) models were used to assess trait stability. GS accuracy (r) was assessed for ridge regression best linear unbiased prediction (rr-BLUP), Bayesian ridge regression (BRR), reproducing kernel hilbert space (RKHS), and elastic net (EN). Across all models, GS produced a wide range of accuracies for trait stability (0.1 to 0.65) that varied by trait and stability method. Accuracy was 0.35 for yield and 0.44 for yield stability using AMMI, indicating the viability of GS in selecting lines with both high and stable yield. Our findings lay the foundation for wheat breeding programs in northeastern U.S.A. to implement GS. It also provides useful information for wheat rust researchers: as phenotypic selection for rust resistance can be both expensive and time consuming and rapid evolution of rust pathogens require an emphasis on durable resistance controlled by multiple genes, the GS approach applicable for complex traits thus has potential to achieve higher gains per unit time than traditional breeding for rust resistance.

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Breeding Studies of Resistant Varieties to Stripe and Stem Rust Diseases in West Transitional Zone of Turkey

Belen Transitional Zone Agricultural Research Institute, Turkey

The most serious wheat diseases affecting yield and quality in West Transitonal Zone of Turkey is rust diseases. Breeding resistant varieties is the most economic and confident way to struggle with these diseases. In this study, it was aimed to determine the genotypes which are resistant to stripe and stem rust diseases existing in our region and use these genotypes as material in breeding program. The study was carried out in 2014 at natural and artificial epidemic conditions in the experimental field of  Transitional Zone Agricultural Research Institute. The reactions of some wheat genotypes to stripe and stem rust diseases caused by the fungal agents P.striformis ve P.graminis were detected. For this purpose,  310 lines and  18 variety of  bread wheat belonging to Transitional Zone Agricultural Researh Institute were sown in a way 1 m x 1 row. The disease assessments were conducted in May-June 2014 according to the Modified Coob Scale. As a result of infection coefficient observations, it was determined that 49% of the material are resistant to stripe rust and 60% of the material are resistant to stem rust.

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Emerging new virulence gene combinations in the Mexican Pst population

Huerta-Espino Campo Experimental Valle de México INIFAP, México

Yellow (stripe) rust continues to be an important disease of wheat in the irrigated EL Bajio region and northwestern Mexico, and in the High Plateau of Central Mexico. Isolate MEX 96.11, virulent to race-specific resistance genes Yr2, Yr3, Yr6, Yr7, Yr9 and Yr27, represented the most prevalent Pst race until 2001 and evolution of new virulences was slow. Several additional R-genes, including a gene in Pollmer triticale, are now defeated. The aggressive Pst race with Yr8 virulence, first detected in the United States in 2000, not only became widespread in Mexico by 2003 but continued to evolve at a more rapid rate with virulence to Yr1 occurring in 2003. However these races did not cause crop losses other than increased levels of head infections in some cultivars. Variants with virulences to Yr17 and Yr31 were detected in 2007 and 2008, respectively. These resistance genes are known to occur in some wheat varieties and breeding materials. 2010 disease data from trap nurseries that included the Avocet isolines and other varieties indicated the existence of virulence for Yr1, 2 (Siete Cerros), 3 (Tatara), 6, 7, 8, 9, 17, 27 and 31 (Rebeca F2000) in different Pst isolates. During the 2014 crop season, an epidemic occurred in farm fields and samples were collected and analyzed in greenhouse tests. Virulence combination V2, 3, 6, 7, 8, 9, 17, 27 and 31 first identified and represented in isolates CEVAMEX14.25 and MEX 14.141, and a similar isolate MEX14.146 virulent to Yr1 were the most frequent. These new virulence combinations caused yield losses in cultivar Nana F2007 grown in the Mexican highlands and Luminaria F2012, released for the irrigated areas of Bajio. Our results indicate a continuing evolution and accumulation of virulences in the aggressive Pst lineage. Determination of the defeated genes in Nana F2007 and Luminaria F2012 is underway.

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The features of wheat rust development and the resistance of local cultivars in Kazakhstan

Koyshibayev Kazakh Research Institute of Plant Protection and Quarantine, Kazakhstan

The climatic conditions of Kazakhstan are suitable to grow the high-quality grain of spring wheat on an area of 12-14 mil.ha. The country’s sharply continental climate limits the wheat yield as well as biotic stresses. Among latter factors, diseases significantly reduce yield up to 25% and more during epyphytoties. In the Northern Kazakhstan the considerable threat for common wheat comes from leaf rust (Puccinia  triticina), stem rust (Puccinia graminis), septoria (Stagonospora nodorum, Septoria tritici), and tan spot (Pyrenophora tritici-repentis); yellow rust (Puccinia striiformis) infects wheat plants in the South and South-east regions, where the winter wheat is more common. Epiphytoties of leaf rust were observed in 2000, 2002, 2005, and 2007. Many years research has led to conclusion that local wheat varieties do not possess resistance to mentioned diseases. Last year screening of 46 cultivars at Kostanay province designated virulence to local pathotypes, except of couple of them (Kazakhstanaskaya 19 and Karabalykskaya 20). Russian varieties (Omskaya 37, Omskaya 39, Omskaya 41, Uralo-sibirskaya, Pamyati Mayestrenka, Lyubava, and Altayskaya zhnitza) demonstrated “slow rusting”. In the period of 2001-2014 the effectiveness to leaf rust was identified using Thatcher isogenic lines under northern Kazakhstan conditions and showed avirulence to local Pt pathotypes in lines carrying Lr9, Lr24, Lr29, Lr35, and Lr37 as well as the pyramid of Lr genes and/or “slow rusting” genes. The essential spread of stem rust was recorded in 2007, 2008, 2013, and 2014. Taking into account the absence of local sources of infection.  In addition, the monitoring of pathogen with use of a set of lines with Sr genes detected the absence of aggressive race within north of Kazakhstan. In order to create resistant cultivars the sources of resistance are recommended to apply from current study.

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