|Wasonga, Charles - GRAD STUDENT,CORNELL UNIV|
|Griffiths, Phillip - CORNELL UNIVERSITY|
|Pastor Corrales, Marcial|
Submitted to: HortScience
Publication Type: Proceedings
Publication Acceptance Date: July 21, 2008
Publication Date: July 21, 2008
Citation: Griffiths, P.D., Pastor Corrales, M.A., Porch, T.G. 2008. Combining Rust Resistance and Heat Tolerance in Snap Beans. HortScience. 43(4):1151. Technical Abstract: Snap bean (Phaseolus vulgaris L.) is an important crop in many countries both in economic and nutritional terms. However, diseases such as rust (Uromyces appendiculatus) and abiotic stresses including high temperatures limit its productivity in many areas in the tropics. Enhancing snap bean resistance to various races of the rust pathogen is a key strategy for mitigating associated yield losses. High temperature stress limits snap bean production both on temporal and spatial scales particularly through its negative effects on the crop’s reproductive development. Increasing tolerance of the crop to high temperature stress is therefore also an important strategy for increasing yields. Presently there are no snap bean cultivars which combine resistance to rust disease and tolerance to heat stress despite occurrence of these production constraints within the same growing environments. The objectives of this study are to: a) transfer two major rust resistance genes (Ur-4 and Ur-11) into heat-tolerant snap bean genotypes to provide protection against majority of races of the rust pathogen and b) develop rust resistant and heat tolerant breeding lines for field testing under East African conditions. Heat-tolerant snap bean breeding lines including ‘Cornell 502’, ‘Cornell 503’ and lines HT045601, HT045603, HT045608, and HT045611 developed from previous diallel studies that combined heat tolerant lines were crossed with two rust resistant snap bean breeding lines (BelJersey-RR-15 and BelFla-RR1-4) containing Ur-4 and Ur-11 rust resistance genes. The populations combining rust resistance with heat tolerance were advanced to the F2 generation and evaluated for heat tolerance under greenhouse conditions. For each of the populations 48 plants were grown in plastic pots together with a set of eight controls each with six plants. Heat tolerant selections from the trial were advanced to F3 generations and then evaluated with SCAR markers for the Ur-11 and Ur-4 genes and the lines identified to contain the two genes advanced to F4 generations. The rust resistant lines from the F3 generations are also being field tested in collaboration with Tim Porch at USDA TARS Mayaguez PR at the University of Puerto Rico site in Juana Diaz. Subsequent selections will be further improved and then field tested in East Africa in 2009.