AUTHOR=Webb Anne , Reynolds Tom R. , Wright Tally I. C. , Caiazzo Rosa , Lloyd David C. , Thomas Jane E. , Wood Thomas A. 

TITLE=Identification of Faba bean genetic loci associated with quantitative resistance to the fungus Botrytis fabae, causal agent of chocolate spot

JOURNAL=Frontiers in Plant Science

VOLUME=15

YEAR=2024

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2024.1383396

DOI=10.3389/fpls.2024.1383396

ISSN=1664-462X

ABSTRACT=<sec><title>Introduction</title><p>Chocolate spot, caused by the ascomycete fungus <italic>Botrytis fabae</italic>, is a devastating foliar disease and a major constraint on the quality and yield of faba beans (<italic>Vicia faba</italic>). The use of fungicides is the primary strategy for controlling the disease. However, high levels of partial genetic resistance have been identified and can be exploited to mitigate the disease.</p></sec><sec><title>Methods</title><p>The partially resistant <italic>V. faba</italic> cultivar Maris Bead and susceptible Egyptian accession ig70726 were crossed, and a genetic mapping population of 184 individuals was genotyped in the F<sub>2</sub> generation and screened for resistance to <italic>B. fabae</italic> infection in the F<sub>3</sub>, F<sub>5</sub>, and F<sub>6</sub> generations in a series of field experiments. A high-density linkage map of <italic>V. faba</italic> containing 3897 DArT markers spanning 1713.7 cM was constructed.</p></sec><sec><title>Results</title><p>Multiple candidate quantitative trait loci (QTLs) in 11 separate regions of the <italic>V. faba</italic> genome were identified; some on chromosomes 2, 3, and 6 overlapped with loci previously linked to resistance to Ascochyta leaf and pod blight caused by the necrotrophic fungus <italic>Ascochyta fabae</italic>. A transcriptomics experiment was conducted at 18 h post-inoculation in seedlings of both parents of the mapping population, identifying several differentially expressed transcripts potentially involved in early stage defence against <italic>B. fabae</italic>, including cell-wall associated protein kinases, NLR genes, and genes involved in metabolism and response to reactive oxygen species.</p></sec><sec><title>Discussion</title><p>This study identified several novel candidate QTLs in the <italic>V. faba</italic> genome that contribute to partial resistance to chocolate spot, but differences between growing seasons highlighted the importance of multi-year phenotyping experiments when searching for candidate QTLs for partial resistance.</p></sec>