1a. Objectives (from AD-416)
The major and long-term objectives of this project are 1) to identify and characterize disease resistance genes in common bean for the management of the soybean rust pathogen (Phakopsora pachyrhizi), (2) to identify and characterize disease resistance genes in common bean for the management of common bean rust (Uromyces appendiculatus), and 3) to use newly discovered and other disease resistance genes to develop common bean germplasm lines with multiple resistances to common bean and soybean rusts and other highly variable pathogens.
1b. Approach (from AD-416)
To identify and characterize disease resistance genes for soybean rust (SBR) control in common bean, a sub sample of the common bean core collection will be evaluated. This core collection will have about 250 bean accessions from the Andean (five countries) and Mesoamerican (six countries) gene pools. Soybean accessions will be included as checks. Several isolates of the SBR pathogen from different countries in Africa, Asia, and South America, and from the United States, will be used to inoculate the common bean accessions. SBR resistant and susceptible accessions will be crossed to characterize the inheritance of SBR resistance and to search for molecular markers linked to the SBR resistance genes. Appropriate populations (F2, RILs, etc.) for these types of studies will be developed and inoculated with selected isolates of the SBR. Leaf tissue from each F2 plant or other appropriate progeny plant will be collected for DNA extraction and the identification of molecular markers linked to SBR resistance genes. To determine yield reduction on common bean caused by SBR, dry bean plots will be established under field conditions in collaboration with scientists from the United States and Brazil. Two locally adapted dry bean cultivars will be used. Locally adapted soybean cultivars will also be included for comparison. Similar methodologies and approach will be used for the identification and characterization of resistance genes in common bean for the control of common bean rust. All the newly discovered genes for resistance to both rusts will be used in the development of new bean cultivars with commercial bean seed type and broad resistance to rusts and other important common bean pathogens.
3. Progress Report
Progress was made in the development and identification of new snap bean lines combining broad resistance to the hyper variable bean rust pathogen and tolerance to high temperatures. Initially, crosses were made to incorporate the Ur-4 and Ur-11 rust resistance genes into eight snap bean germplasm lines having tolerance to high temperatures. Previous research has shown that combining these two genes result in broad resistance to all known strains of the bean rust pathogen. The Ur-4 gene is from the Andean (South America) gene pool and Ur-11 gene from the Middle American (Central America and Mexico) pool. A total of 55 F3 lines were evaluated with phenotypic markers for the presence of the resistance genes. Several lines had either the Ur-4 or Ur-11 genes but 10 F3 lines combined both rust resistance genes. These lines were selected for further evaluations and probable release. This is a collaborative project with Cornell University and ARS-Puerto Rico. Progress was made in the characterization of two new strains (races) of the rust pathogen that appeared under field conditions at the end of the 2007 and 2008 planting seasons in Michigan and North Dakota, respectively. These are the leading U.S. dry bean production states. Characterization of these races was accomplished using an established international set of six Andean and six Middle American bean differential cultivars. Further studies followed the characterization of both races. Both new strains infected most dry bean varieties grown in North Dakota and Michigan and the rest of the U.S. Many of these varieties were previously resistant to the rust disease. The reactions of most commercial and newly developed bean varieties of different market classes grown in the U.S. (pinto, great northern, black, navy, etc.) were evaluated with these two new strains. The reaction of most rust resistance genes available for breeding dry and snap beans with resistance to the rust disease was also evaluated. This research has been conducted in close collaboration with Michigan State University and North Dakota State University. Progress was made in combining various bean rust resistance genes in bean lines of the small-red market class. All known current small-red dry bean varieties grown in the U.S. are highly susceptible to bean rust. The very effective Middle American Ur-11 rust resistance gene was combined with the Middle American Ur-3 gene which is also of Middle American origin and other Andean and Middle American resistance genes in small red dry bean lines. Several lines with commercial color typical of the small-red market class combining two and three rust resistance genes were selected for further evaluations.
1. Development of common bean germplasm lines combining genes for resistance to bean rust and other major diseases. Diseases are one of the principal constraints to common bean production. A research project was initiated by ARS at Beltsville Agricultural Research Center with collaborators at the University of Nebraska to develop common bean germplasm lines with resistance to bean rust and other major diseases of dry beans in the U.S. Bean lines previously developed at the USDA Beltsville combining three and four rust resistance genes with two genes for resistance to bean common mosaic and bean common mosaic necrosis potyviruses were hybridized with beans developed at the University of Nebraska which carry resistance to common and halo bacterial blights and white mold. A combination of traditional (phenotypic) selection and molecular marker analysis was used to confirm the presence of the disease resistance genes. A total of 34 advanced lines have been developed each carrying three or four rust resistance genes. The presence of the rust resistance genes was confirmed using phenotypic markers. In addition to resistance to the bacterial diseases and white mold, all lines had the Middle American Ur -3 and Ur-11 and the Andean Ur-6 rust resistance genes. Fourteen bean germplasm lines were of the great northern and 20 of the pinto market classes. The great northern lines also had the Andean Ur-4 rust resistance gene. The unique resistance gene combinations provide resistance to all known strains of the bean rust, bean common mosaic, and common mosaic necrosis viruses. The potential impact of these great northern and pinto bean germplasm lines on solving significant disease problems facing U.S. common bean production is very significant.
Goncalves-Vidigal, M.C., Vidigal Filho, P.S., Pastor Corrales, M.A. 2008. A New Anthracnose Resistance Gene in Andean Common Bean Cultivar Jalo Listras Pretas. Crop Science. 49:133-138.