Accelerated breeding of black rot resistant brassicas for the benefit of east African smallholders

Lead Research Organisation: Harper Adams University
Department Name: Crops and Environment Sciences

Abstract

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Technical Summary

This multidisciplinary project will combine expertise in genetics, breeding, genomics and pathology to generate novel information on quantitative resistance to black rot caused by Xanthomonas campestris pv. campestris, a major disease of Brassicas. Quantitative resistance, involving the cumulative phenotype expressed by numerous genes, is generally expected to be more durable than resistance due to single dominant genes. However, this kind of resistance is more difficult to exploit in breeding programmes. We will dissect the resistance in Brassica rapa into major components and determine their relative contribution. We will utilise new developments in B. rapa genomics and emerging information on synteny between the Brassica and Arabidopsis genomes to fine- map and identify the genes involved. The spectrum of the resistance will be determined against a wide range of pathogen isolates from our culture collection. Representative sets of the Brassica genepool will be screened to identify allelic variation and potential new candidates for resistance breeding. Well defined resistant germplasm with tightly linked molecular markers and information on allelic variation in Brassica genomes will be key practical outcomes. Specific objectives of this study are: 1. Characterisation of the major components of quantitative Xanthomonas campestris pv. campestris (Xcc) race 1 and race 4 resistance from Brassica rapa; 2. Fine-scale mapping to identify closely linked markers and candidate genes using synteny between the Arabidopsis and Brassica genomes. 3. Clone candidate genes and transform into B. oleracea for functional testing in a C genome recipient. 4. Assess the broad spectrum potential of the B. rapa resistance for protection against a range of Xcc isolates. 5. Survey allelic variation for resistance loci in other Brassica genomes using Brassica Differential Fixed Foundation Sets (DFFS)

Publications

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Description The grant provided training and resources to significantly improve the capability of KARI pathologists to identify and characterise Xcc and the opportunity to develop further research links in this area.
Exploitation Route Our findings on the race structure and distribution of the xcc pathogen in sub-Saharan Africa will assist plant breeders in choosing suitable germplasm and targets for resistance breeding, and provide information to extension specialists advising farmers on suitable Brassica cultivars for planting.

The training of a KARI visiting scientist in the identification of Xcc race types and protocols for DNA sample preparation will give the organisation the capacity to train local pathologists in these diagnostic techniques.
Sectors Agriculture, Food and Drink