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Project
Update on "Genetic Improvement of Bush and Climbing Beans"
by
Robin Buruchara, CIAT, Uganda; Email: R. BURUCHARA@CGIAR.ORG
The
objective and major outputs by of the Rockefeller Foundation funded
project on “Increasing
Food Security and Rural Incomes in Eastern, Central and Southern Africa
through Genetic Improvement of Bush and Climbing Beans’ are presented below.
Project
objectives
1.
Define the composition and distribution of Pythium species
causing root rots of common bean in Uganda, Rwanda and Kenya
2.
Develop standardized molecular markers for defining and
characterizing the angular leaf spot pathogen, Phaeoisariopsis
griseola
3.
Characterize the nature and inheritance of angular leaf spot
resistance in common bean and develop molecular markers for marker
assisted selection breeding
4.
Combine and pyramid angular leaf spot, Pythium root rot and
Fusarium wilt resistance into bean varieties that are preferred in the
region (market class beans).
5.
Disseminate the results to scientists from participating
countries and bean researchers through a series of workshops and student
training.
Major Outputs:
·
Nineteen Pythium
species, including known bean pathogens, putative new species and two
potential biological control agents, were identified by sequencing the
ITS1 and ITS2 regions of the ribosomal DNA of 130 isolates associated
with common bean affected with Pythium root rot in Kenya, Rwanda and
Uganda.
·
Seven locus-specific microsatellite derived markers that
can distinguish the main pathogen groups (Andean and Mesoamerican) of Phaeoisariopsis
griseola, the causal agent of angular leaf spot disease, and between
the pathogen groups found in Africa from those found in Latin America were
developed and are being validated before being widely used in
pathogen characterization in Africa.
·
Several resistance genes against P.
griseola, that are controlled by major genes that are either
dominant or recessive; acting singly or duplicated, and which may
interact in an additive manner, with or without epistasis were
identified in 12 genotypes including Mex 54, an important source of resistance in Africa, which appears to have more
(recessive and dominant) than one resistant gene.
·
RAPDs,
SSR and AFLP markers linked
to some of the angular leaf spot resistance genes were identified in
promising parental lines (Mex 54, MAR 1, G 10474, G 1090) and SCARs for some of these markers have been developed and their utility for MAS is being evaluated.
·
Several populations were developed to transfer, combine
and pyramid resistance to angular leaf spot, Pythium root rot, fusarium
wilt into a number of locally adapted but susceptible commercial bush
and climbing bean cultivars.
·
Two workshops/courses have been conducted to train project
and bean networks partners on the use of biotechnological tools in bean
improvement: firstly, on application of molecular techniques in pathogen
characterization and secondly, in marker assisted selection where,
markers developed for ALS resistance were successfully tested, potential
for marker assisted selection breeding under different settings
evaluated, and an inventory made of the potential of MAS in bean
breeding in Africa, traits that are likely to benefit from MAS,
genotypes for which markers are available and when and where markers
have a comparative advantage in breeding.
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