Chocolate spot: Pathogenicity dynamics, population diversity and host resistance to Botrytis fabae

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Chocolate spot, caused by Botrytis fabae, is an important disease of faba bean (Vicia faba) which can cause severe crop losses. B. fabae has a narrow host range with faba bean being the most economically important host.Currently there are no resistant commercial cultivars available, although partially resistant lines have been identified in the UK and elsewhere. However, it is currently unknown if this resistance is universally effective or whether strain specificity occurs. Published results of resistance screens, including partially resistant faba bean lines, have been inconclusive or contradictory, which suggest that the latter may be the case.Aim/approach: This project will investigate whether strain -specific resistance to B. fabae occurs by a) improving the knowledge on genetic resistance in the host (establishing the genetic basis of resistance in partially resistant lines), b) extend screening for novel sources of resistance in Vicia faba, and by c) studying differential virulence in the pathogen. The project will also investigate host-pathogen interactions to identify putative effector molecules by constructing a de novo genome assembly and mapping reads from transcriptomic analyses onto this.The student will attempt to identify the location Quantitative trait loci (QTL) and characterise the genetic basis of resistance of chocolate spot resistance in selected mapping populations. Screening for chocolate spot resistance in a more extensive number of cultivars will aid identification of potential novel sources of resistance.In conjunction with identifying sources of resistance in the host, the genetic diversity and potential for differential virulence in the pathogen will be explored. Although B. fabae has been included in taxonomic studies of the Botrytis genus, no large-scale studies to examine this pathogen's genetic diversity have so far been undertaken . NIAB holds a steadily growing collection of more than 200 UK-isolates of B. fabae which will form the basis of the student's efforts to characterise the genetic diversity mainly within the UK's populations of B. fabae. This will involve the identification of differential virulence through screening of panels of Vicia faba as well as studying the pathogen's diversity on a morphological, molecular and genomic level.The project will enable us to address the following questions including:How genetically diverse is Botrytis fabae within the UK and compared to other countries??Are there distinct strains of B. fabae with differential virulence profile?How are these distributed geographically across the UK and does that distribution change over time and to what extent?Which genes in B. fabae are contributing to virulence/pathogenesis