projects - cabi...protect against a range of black rot isolates. we also aim to fine-map the...

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KNOWLEDGE FOR LIFE RESEARCH projects Cabbage ( Brassica oleracea ssp. capitata) and kales ( B. oleracea ssp. acephala) are key crops for smallholder farmers in East Africa both for home consumption and to generate income. so what’s the problem? Black rot caused by the bacterium Xanthomonas campestris pv. campestris (Xcc) is the most serious threat to brassica production in East Africa. Losses in excess of 90% have been reported in susceptible varieties. The disease is seed-borne meaning that cultural control methods are less effective. Therefore, deploying resistant varieties is the most effective management strategy, although this strategy is complicated by the high variability of the pathogen. what is this project doing? This multidisciplinary project combines expertise in genetics, breeding, genomics and pathology to generate new information on quantitative resistance – a way of determining the ranges of resistance – to black rot. The major objectives include determining the race structure of the East African strain of black rot. Because cabbages and kales are highly susceptible to black rot while Chinese cabbage (Brassica rapa) is not, our studies will concentrate on charactering factors essential for resistance and the potential of this resistance to protect against a range of black rot isolates. We also aim to fine-map the original identified genomic regions that control this resistance to identify the closely linked molecular markers that can be used in plant breeding. Finally, we will identify black rot resistant varieties for cabbage and kale breeding programmes in East Africa. Combined, this information will help the region’s breeders to develop and deploy potentially resistant brassicas. breeding black rot resistant brassicas locations UK – scientific experiments Kenya, Tanzania, Uganda – field experiments dates March 2008 – March 2012 CABI project team Joseph Mulema Daniel Karanja Lucy Karanja Duncan Chacha

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Page 1: projects - CABI...protect against a range of black rot isolates. We also aim to fine-map the original identified genomic regions that control this resistance to identify the closely

KNOWLEDGE FOR LIFE

research projects

Cabbage (Brassica oleracea ssp. capitata) and kales (B. oleracea ssp. acephala) are key crops for smallholder farmers in East Africa both for home consumption and to generate income.

so what’s the problem?Black rot caused by the bacterium Xanthomonas campestris pv. campestris (Xcc) is the most serious threat to brassica production in East Africa. Losses in excess of 90% have been reported in susceptible varieties. The disease is seed-borne meaning that cultural control methods are less effective. Therefore, deploying resistant varieties is the most effective management strategy, although this strategy is complicated by the high variability of the pathogen.

what is this project doing?This multidisciplinary project combines expertise in genetics, breeding, genomics and pathology to generate new information on quantitative resistance – a way of determining the ranges of resistance – to black rot.

The major objectives include determining the race structure of the East African strain of black rot. Because cabbages and kales are highly susceptible to black rot while Chinese cabbage (Brassica rapa) is not, our studies will concentrate on charactering factors essential for resistance and the potential of this resistance to protect against a range of black rot isolates. We also aim to fine-map the original identified genomic regions that control this resistance to identify the closely linked molecular markers that can be used in plant breeding. Finally, we will identify black rot resistant varieties for cabbage and kale breeding programmes in East Africa. Combined, this information will help the region’s breeders to develop and deploy potentially resistant brassicas.

breeding black rot resistant brassicas

locationsUK – scientific experiments Kenya, Tanzania, Uganda – field experiments

datesMarch 2008 – March 2012

CABI project teamJoseph Mulema Daniel Karanja Lucy Karanja Duncan Chacha

Page 2: projects - CABI...protect against a range of black rot isolates. We also aim to fine-map the original identified genomic regions that control this resistance to identify the closely

contactCABI, ICRAF Complex, United Nations Avenue, Gigiri, PO Box 633-00621, Nairobi, Kenya T: +254 20 72 24450 F: +254 20 71 22150 E: [email protected] www.cabi.org/africa ID

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results so farA survey of black rot status was conducted on smallholder farms in East Africa, from which a total of 250 isolates of the bacterium (141, 79 and 30 isolates from Kenya, Tanzania and Uganda respectively) were isolated and categorized. Race 1 was observed in Kenya and Tanzania while race 4 was observed in the three countries. Genomic fingerprinting with repetitive-PCR (a type of polymerase chain reaction that targets the repetitive sequences in bacterial genomes) revealed clusters that did not depict significant correlations between isolates and geographical location, isolates and host adaptation or isolates and race. It did however demonstrate existence of genetic differences within the East African black rot strains indicating that it is not just a cloned population.

Next, assessments of field resistance to black rot of third-generation brassicas bred during the project, cabbage and kale varieties commonly grown in East Africa, and pre-breeding cabbage and kale lines will be undertaken. This will involve replicated field trials over two seasons in Kenya. Ongoing work involves fine mapping of the identified genomic regions.

www.cabi.org/blackrot

Joseph Mulema, Project Manager

partnersHarper-Adams University College

University of Warwick

Kenya Agricultural Research Institute (KARI)

Food and Environment Research Agency (FERA) in the UK

The World Vegetable Centre – Regional Centre for Africa (AVRDC-RCA)

sponsorsBiotechnology and Biological Sciences Research Council (BBSRC)

Department for International Development (DfID)