Indirect Evidence Based on Mating-Type Ratios for the Role of Sexual Reproduction in European and Chinese Populations of Plenodomus biglobosus (Blackleg of Oilseed Rape)

A - Papers appearing in refereed journals

King, K. M., Canning, G., Zhou, K., Liu, Z., Wu, M. and West, J. S. 2023. Indirect Evidence Based on Mating-Type Ratios for the Role of Sexual Reproduction in European and Chinese Populations of Plenodomus biglobosus (Blackleg of Oilseed Rape). Pathogens. 12 (1), p. 3. https://doi.org/10.3390/pathogens12010003

AuthorsKing, K. M., Canning, G., Zhou, K., Liu, Z., Wu, M. and West, J. S.
Abstract

Blackleg (Phoma) disease, caused by the ascomycete fungi Plenodomus biglobosus and P. lingam, threatens oilseed rape (OSR; Brassica napus) crops internationally. In many parts of the world, both species co-occur, but in China only P. biglobosus has so far been reported. Plenodomus biglobosus reproduces asexually (pycnidiospores), but also sexually (pseudothecia-yielding ascospores), via a heterothallic mating system requiring MAT1-1 and MAT1-2 genotypes. However, the roles of airborne ascospore inoculum in driving blackleg disease outbreaks in China are less well understood compared to elsewhere in the world. This is despite the very different agronomic cropping practices in parts of China, in which paddy rice and OSR are often grown in rotation; OSR stubble is often submerged under water for long periods potentially affecting pseudothecial development. Here, we indirectly investigate the potential role of sexual reproduction by developing new polymerase chain reaction (PCR) -based mating-type diagnostics for P. biglobosus and subsequently screening an international collection of 59 European and 157 Chinese isolates. Overall, in both Europe and China, P. biglobosus mating types did not deviate from a 1:1 ratio, such as is generally thought to occur under frequency-dependent selection in sexually reproducing pathogen populations. Both mating types were balanced in all the individual European countries tested (Austria, France, Poland, UK). Conversely, in China, mating types were only balanced in the eastern region; in the northern and southwestern regions there were skewed ratios, more typical of predominantly asexual reproduction, towards MAT1-1 and MAT1-2, respectively. The implications of these findings and future research directions for improved understanding of P. biglobosus epidemiology on OSR, particularly in China, are considered.

KeywordsBlackleg; Epidemiology; Heterothallic; Leptosphaeria biglobosa; Mating type; Oilseed rape; Phoma; Sexual reproduction
Year of Publication2023
JournalPathogens
Journal citation12 (1), p. 3
Digital Object Identifier (DOI)https://doi.org/10.3390/pathogens12010003
Open accessPublished as ‘gold’ (paid) open access
FunderBiotechnology and Biological Sciences Research Council
Funder project or codeBBSRC Strategic Programme in Smart Crop Protection
Publisher's version
Supplemental file
Output statusPublished
Publication dates
Online20 Dec 2022
Publication process dates
Accepted12 Dec 2022
PublisherMDPI
ISSN2076-0817

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