Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/8/2010
Publication Date: 11/23/2010
Publication URL: http://journal.ashspublications.org/cgi/content/abstract/135/6/521
Citation: Pastor Corrales, M.A., Wasonga, C.J., Porch Clay, T.G., Griffiths, P.D. 2010. Targeting gene combinations for broad spectrum rust resistance in heat tolerant snap beans developed for tropical environments. Journal of the American Society for Horticultural Science. 135(6):521-532. Interpretive Summary: Snap beans are grown extensively in temperate regions for fresh-market and processing and also in tropical and sub-tropical regions including Southern and Eastern African countries, where they are a significant source of income for both small holder and large scale farmers. The bean rust disease is a major constraint to snap bean production in the U.S. and all snap bean production countries in Eastern and Southern Africa. In addition to rust, heat stress often occurs within the same production regions and significantly reduces snap bean yield due to the use of cultivars that are not heat tolerant. The objective of this study was to improve tropical snap bean production through the combination of rust resistance and heat tolerance in the same snap bean cultivars. To accomplish this objective we used previously developed ARS-rust resistant snap beans and Cornell University-heat tolerant snap beans to generate new snap beans that combine both attributes. During the evaluation process we identified snap beans that had two genes for rust resistance coupled with heat tolerance. The broad resistance to rust in these snap beans will be effective in the U.S. as well as in Eastern and Southern Africa. These newly developed snap bean germplasm lines represent a unique combination of rust resistance and heat tolerance that has the potential to increase snap bean production and can be used by snap bean breeders to produce new rust resistant and heat tolerant cultivars.
Technical Abstract: The Common bean rust disease, caused by Uromyces appendiculatus, and heat stress, caused by high ambient temperature, constrain snap bean (Phaseolus vulgaris L.) production in many areas in tropical and temperate zones. Bean rust and heat stress often occur within the same production regions, such as Eastern Africa, and significantly reduce snap bean yield due to the use of susceptible cultivars. The objective of this study was to improve tropical snap bean production through the combination of rust resistance and heat tolerance in the same genetic background. Breeding populations were developed from ARS-USDA snap bean germplasm lines BelJersey-RR-15 and BelFla-RR-1, containing the Ur-4 and Ur-11 rust resistance genes, and heat tolerant snap bean breeding lines HT601, HT603, HT608 and HT611. Eight populations were generated and evaluated for heat tolerance in the F2 and F3 generations. Generation means analysis was used to select the heat tolerant lines that were evaluated for the presence of the Ur-4 and Ur-11 rust resistance genes in the F4 generation. Four F5 lines were identified to be homozygous for the Ur-4 and Ur-11 genes and tolerant to high temperature. The snap bean germplasm developed represents a unique combination of rust resistance and heat tolerance that has the potential to increase production.