2008 Annual Report
This research addresses three of the four components of National Program 303, Plant Diseases; Component 1. Disease Diagnosis: Detection, Identification and Characterization of Plant Pathogens; Component 2. Biology, Ecology, Epidemiology, and Spread of Plant Pathogens and Their Relationships with Hosts and Vectors; and Component 3: Plant Disease Resistance.
Stem rust resistance gene Sr36 in wheat is important because it is highly effective against Ug99 and a major component for Ug99 resistance in U.S. soft winter wheat. The occurrence of a combination of virulence on Sr36 and Sr31 (as well as the virulence combination of Sr24 and Sr31 detected in 2006) has substantially increased the vulnerability of wheat to stem rust worldwide, raised serious concerns on the potential impacts.
NP 303 - Problem Statement 3B. Disease resistance in new germplasm and varieties.2. New, effective crown rust resistance found in wild tetraploid slender oat, Avena barbata. Crown rust caused by Puccinia coronata is the most destructive disease of oat worldwide. Resistant oat varieties quickly succumb to new races of the pathogen, so new resistance genes are needed. The USDA collection of A. barbata was screened for resistance to a very diverse population of P. coronata. Forty-eight accessions were found to be resistant to this population which contained virulence to all the described crown rust resistance genes in cultivated oat. A. barbata represents a new, unexploited pool of novel resistance genes that can be used in oat improvement programs in the U.S. and elsewhere.
NP 303 - Problem Statement 3B. Disease resistance in new germplasm and varieties.3. Microarray developed for the wheat stem rust pathogen, Puccinia graminis f. sp. tritici.
Stem rust is a potentially devastating disease, having been responsible for several historical, destructive epidemics. The development of genomic tools to better understand the genetic basis for pathogenicity and the obligate parasitic nature of P. graminis represents a significant advance. A microarray containing approximately 21,000 predicted genes from the annotated genome sequence of P. graminis f. sp. tritici was developed and preliminary analysis of the array has been completed. This microarray will be a crucial tool for dissecting genes involved in pathogenicity and their expression during disease development, and could pave the way for novel approaches to controlling rust diseases of crops.
NP303 - Problem Statement 2A: Pathogen Biology, Virulence Determinants, and Genetics of the Pathogen.4. Genetic variation in populations of wheat leaf rust (Puccinia triticina) in North and South America indicate pathogen migration between the two continents.
Leaf rust of wheat, caused by Puccinia triticina is the most common disease of wheat in the U.S. and world-wide. Isolates of P. triticina from the U.S. and South America were analyzed using virulence to specific resistance genes and molecular markers. Over 90% of isolates in both continents were placed into two different groups, with no significant genetic differentiation between isolates from the two continents in either group. Isolates of leaf rust that first appeared in the mid 1990s in the U.S. were found to be closely related to isolates that first appeared in South America in the late 1990s. It is highly likely that recent migration of leaf rust between the U.S. and South America has occurred, although weather and wind patterns would not predict regular movement of spores between continents. Races of leaf rust selected by host resistance genes in one continent may easily migrate and infect wheat cultivars in the U.S. The high degree of virulence variation in P. triticina populations indicates the need for use of non-specific resistance in wheat cultivars to minimize yield losses.
NP 303 - Problem Statement 3B. Disease resistance in new germplasm and varieties.5. Mapping and designation of leaf rust resistance genes in wheat.
Leaf rust of wheat, caused by Puccinia triticina is the most common disease of wheat in the U.S. and world-wide. Over 60 races of leaf rust are identified annually in the U.S. as a result most of the Lr resistance genes in wheat cultivars in the U.S. do not condition effective resistance. A leaf rust resistance gene in bread wheat line RL6137 that was originally derived from Triticum monococcum was mapped to chromosome 3AS in wheat, and was officially designated as Lr63. A leaf rust resistance gene in wheat line RL6149 originally derived from durum wheat was mapped to chromosome 6AL in wheat and officially designated as Lr64. Both genes Lr63 and Lr64 condition effective resistance to most of the leaf rust races in the U.S. and will be useful for improving leaf rust resistance in U.S. wheat cultivars.
NP 303 - Problem Statement 3B. Disease resistance in new germplasm and varieties.
5.Significant Activities that Support Special Target Populations
Baenziger, P., Beecher, B., Graybosch, R.A., Ibrahim, A., Nelson, L., Jin, Y., Wegulo, S., Watkins, J., Chen, M., Bai, G. 2008. Registration of 'NE01643' Wheat. Journal of Plant Registrations 2:36-42.
Jin, Y., Szabo, L.J., Pretorious, Z., Singh, R., Fetch, Jr., T. 2008. Detection of Virulence to Resistance Gene Sr24 within Race TTKS of Puccinia graminis f. sp. tritici. Plant Disease. 92:923-926.
Zhang, X., Singh, R., Kolmer, J.A., Huerta-Espino, J., Jin, Y., Anderson, J. 2008. Inheritance of Leaf Rust Resistance in the CIMMYT Wheat Weebill 1. Crop Science. 47:1037-1047.
Zhang, X., Jin, Y., Rudd, J., Bockelman, H.E. 2008. New fusarium head blight resistance spring wheat germplasm identified in the USDA National Small Grain Collection. Crop Science. 48:223-235.
Fetch, T.G., Jin, Y. 2007. International system of nomenclature for Puccinia graminis f. sp. avenae. Plant Disease. 91:763-766.
Jin, Y., Singh, R.P., Ward, R.W., Wanyera, R., Kinyua, M., Njau, P., Fetch, T., Yahouyi, A., Pretorious, Z. 2007. Characterization of seedling infection types and adult plant infection responses of known Sr genes to race TTKS of Puccinia graminis f. sp. tritici. Plant Disease. 91:1096-1099.
Steffenson, B.J., Olivera, P., Roy, J., Jin, Y., Smith, K., Muehlbauer, G. 2007. A walk on the wild side: mining wild wheat and barley collections for rust resistance genes. Australian Journal of Agricultural Research. 58:532-544.
Tsilo, T.J., Jin, Y., Anderson, J.A. 2007. Microsatellite markers linked to stem rust resistance allele Sr9a in wheat. Crop Science. 47:2013-2020.
Kolmer, J.A., Ordonez, M.E. 2007. Genetic differentiation of Puccinia triticina populations in Central Asia and the Caucasus. Phytopathology. 97:1141-1149.
Zhang, X., Singh, R.P., Kolmer, J.A., Huerta-Espino, J., Jin, Y., Anderson, J.A. 2008. Genetics of leaf rust resistance in CIMMYT "Brambling" wheat. Plant Disease. 92:1111-1118.
Kolmer, J.A., Long, D.L., Hughes, M.E. 2008. Physiologic Specialization of Puccinia triticina on Wheat in the United States in 2006. Plant Disease. 92:1241-1246.
Barnes, C.W., Szabo, L.J. 2008. A Rapid Method for Detection and Quantification of Bacterial DNA in Rust Fungal DNA Samples. Phytopathology. 98:115-119.
Castell-Miller, C., Szabo, L.J., Gale, L.R., O'Neill, N.R., Samac, D.A. 2008. Molecular variability of a Minnesota population of Phoma medicaginis var. medicaginis, the causal agent of spring black stem and leaf spot of alfalfa. Canadian Journal of Plant Pathology. 30:85-96.
Carson, M.L. 2008. Virulence Frequencies in Oat Crown Rust in the United States from 2001 through 2005. Plant Disease. 97:379-384.
Tsilo, T.J., Jin, Y., Anderson, J.A. 2008. Diagnostic microsatellite markers for detection of stem rust resistance gene Sr36 in diverse genetic backgrounds of wheat. Crop Science. 48:253-261.
Klindworth, D.L., Miller, J., Jin, Y., Xu, S.S. 2007. Chromosomal locations of genes for stem rust resistance in monogenic lines derived from tetraploid wheat accession ST464. Crop Science. 47:1441-1450.
Szabo, L.J., Koike, S.T., Hill, J.P. 2008. Rust. In: Schwartz, H.F, Mohan, S.K., editors. Compendium of Onion and Garlic Diseases and Pests. 2nd Edition. Minneapolis, Minnesota: APS Press. p. 41-44.
Bonman, J.M., Bockelman, H.E., Jin, Y., Hijmans, R.J., Gironella, A. 2007. Geographic Distribution of Stem Rust Resistance in Wheat Landraces. Crop Science. 47:1955-1963.