Submitted to: Euphytica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 28, 2004
Publication Date: May 28, 2004
Citation: Aggarwal, V.D., Pastor-Corrales, M.A., Chirwa, R.M. and Buruchara, R.A. 2004. Andean beans (Phaseolus vulgaris) with resistance to the angular leaf spot pathogen (Phaeoisariopsis griseola) in Southern and Eastern Africa. Euphytica 136: 201-210.
Interpretive Summary: In Malawi and other countries of Eastern and Southern Africa, the common bean is a major source of dietary protein, fiber, and complex carbohydrates to millions of women, men and children. Among the many constraints that reduce bean production in Africa, a disease known as angular leaf spot (ALS) is the most significant. The fungus that causes ALS has many strains that are genetically different. That is why a bean variety that is resistant in one location or year, maybe susceptible in another. In this study, we report the first bean variety, known as CAL 143, with resistance to the ALS disease in Malawi. This is a bean of the Andean type with large seeds, which are preferred in Malawi. CAL 143 was also found to be ALS resistant in South Africa, Tanzania, and Zambia but not in Uganda. The strains of the ALS pathogen that rendered CAL 143 susceptible in Uganda were not found in other African countries. This was discovered while exploring the strain diversity of the ALS pathogen in several countries in Eastern Africa. We found several different strains in Malawi but none caused ALS on CAL 143. Although most of the strains found in Uganda were different from those found in Malawi, they did not cause ALS on CAL 143, except for one strain that was virulent on CAL 143. We also report here two additional Andean types, AND 277 and AND 279 that were found later to be resistant to ALS in Malawi. CAL 143 has been released as a variety for use by farmers in Malawi.
We identified CAL 143 as the first Andean bean with resistance to the angular leaf spot disease (ALS) in Malawi. ALS, caused by the fungus Phaeoisariopsis griseola, is the most widespread and economically important disease of common bean (Phaseolus vulgaris) in Eastern and Southern Africa. CAL 143 was also resistant to ALS in South Africa, Tanzania, and Zambia but was susceptible in Uganda. This was attributed to the presence in Uganda of races of the ALS pathogen not present in the other countries. We identified two additional Andean bean lines, AND 277 and AND 279, with resistance to ALS in Malawi. The resistance in these two lines and CAL 143 might have come from the same donor parent. We also characterized the virulence diversity of 15 isolates of P. griseola from Southern and Eastern Africa into 9 different races. Five of six isolates from Malawi, and two of seven from Uganda, obtained from large-seeded Andean beans were characterized into four different races of the ALS pathogen considered Andean: these races were compatible only or mostly with large-seeded Andean differential cultivars. The other isolates from Uganda, Malawi, and the Democratic Republic of Congo were from small or Medium-seeded Middle American beans that were characterized into four different races considered Middle American: they were compatible with both Middle American and Andean differential cultivars. CAL 143 was resistant or intermediate under greenhouse conditions to all but one isolate of the ALS pathogen from Uganda obtained from a medium-seeded Middle American bean.