The common bean (Phaseolus vulgaris L.) is an important crop grown widely in Uganda. It is
also an important source of income for smallholder farmers particularly women. Despite its
importance, production in the cool highland regions is constrained by anthracnose disease
which causes losses in both the quantity and the quality of beans produced. The principal aim of
this research was to elucidate on the status of dry bean anthracnose and the genetics
governing its resistance.
A participatory rural appraisal study was conducted to explore farmers' knowledge, experience,
problems and cultivar preferences in association with managing dry bean anthracnose disease. This
study revealed that anthracnose is an important constraint to production which is not controlled in any
way. Although farmers have varying cultivar preferences, they use mostly home saved seed and only
1% could access improved seed. The study suggested the need for practical approaches in the
provision of quality anthracnose resistant seed in consideration of farmers' preferences and the
dynamics of their rural livelihoods.
A study was conducted to determine the variability of the anthracnose (Colletotrichum
lindemuthianum) pathogen in some of the major bean growing regions of Uganda. Use was
made of a set of 12 internationally accepted anthracnose differential cultivars to identify the
physiological races present. The results obtained indicated the presence of eight races with one
race (767) being dominant and most aggressive. Differential cultivars AB 136 and G2333 were
resistant to all the eight races, and can be utilised as potential sources of resistant genes.
A germplasm collection of mostly Ugandan accessions was screened for anthracnose
resistance. Using the area under disease progression curve as the tool for assessing disease
severity, eleven accessions were identified that posses good levels of anthracnose resistance.
The yield loss attributed to the anthracnose disease was determined on three susceptible
Ugandan market-class dry bean cultivars and two resistant cultivars. The results showed that
the yield of susceptible cultivars was reduced by about 40% and an almost equivalent yield was
lost due to poor quality seed. In comparison, the yield lost by the resistant cultivars was not
significant. The study suggested the use of resistant cultivars as the best solution in combating
anthracnose resistance.
Three susceptible Ugandan market class dry bean cultivars and six resistant cultivars were
used for the study of the inheritance of resistance to the anthracnose pathotype 767 in a
complete 9x9 diallel design. The results clearly indicated that the resistance was predominately
conditioned by additive gene action. It was also established that epistatic gene action was
important. More than one pair of genes displaying partial dominance were responsible for
determining resistance and the maternal effect did not have an influence on resistance.
Additionally, the result showed that some of susceptible cultivars combined very well with the
resistant cultivars and that anthracnose resistance heritability estimates in both the narrow and
broad sense were high. These results suggested that the use of simple pedigree breeding
procedures such as backcross selection could be useful in improving anthracnose resistance
levels in the Ugandan market class varieties. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/4501 |
| Date | January 2006 |
| Creators | Nkalubo, Stanley. |
| Contributors | Melis, Rob W., Laing, Mark D. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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