AUTHOR=Lu Lu , Choi Su Ryun , Lim Yong Pyo , Kang Si-Yong , Yi So Young 

TITLE=A GBS-based genetic linkage map and quantitative trait loci (QTL) associated with resistance to Xanthomonas campestris pv. campestris race 1 identified in Brassica oleracea

JOURNAL=Frontiers in Plant Science

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2023.1205681

DOI=10.3389/fpls.2023.1205681

ISSN=1664-462X

ABSTRACT=<p>The production of <italic>Brassica oleracea</italic>, an important vegetable crop, is severely affected by black rot disease caused by the bacterial pathogen <italic>Xanthomonas campestris</italic> pv. <italic>campestris</italic>. Resistance to race 1, the most virulent and widespread race in <italic>B. oleracea</italic>, is under quantitative control; therefore, identifying the genes and genetic markers associated with resistance is crucial for developing resistant cultivars. Quantitative trait locus (QTL) analysis of resistance in the F<sub>2</sub> population developed by crossing the resistant parent BR155 with the susceptible parent SC31 was performed. Sequence GBS approach was used to develop a genetic linkage map. The map contained 7,940 single nucleotide polymorphism markers consisting of nine linkage groups spanning 675.64 cM with an average marker distance of 0.66 cM. The F<sub>2:3</sub> population (N = 126) was evaluated for resistance to black rot disease in summer (2020), fall (2020), and spring (2021). QTL analysis, using a genetic map and phenotyping data, identified seven QTLs with LOD values between 2.10 and 4.27. The major QTL, <italic>qCaBR1</italic>, was an area of overlap between the two QTLs identified in the 2<sup>nd</sup> and 3<sup>rd</sup> trials located at C06. Among the genes located in the major QTL interval, 96 genes had annotation results, and eight were found to respond to biotic stimuli. We compared the expression patterns of eight candidate genes in susceptible (SC31) and resistant (BR155) lines using qRT-PCR and observed their early and transient increases or suppression in response to <italic>Xanthomonas campestris</italic> pv. <italic>campestris</italic> inoculation. These results support the involvement of the eight candidate genes in black rot resistance. The findings of this study will contribute towards marker-assisted selection, additionally the functional analysis of candidate genes may elucidate the molecular mechanisms underlying black rot resistance in <italic>B. oleracea</italic>.</p>