Development of a specific marker for detection of a functional AvrLm9 allele and validating the interaction between AvrL
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ORIGINAL ARTICLE
Development of a specific marker for detection of a functional AvrLm9 allele and validating the interaction between AvrLm7 and AvrLm9 in Leptosphaeria maculans Fei Liu1 · Zhongwei Zou1 · Shuanglong Huang1 · Paula Parks1 · W. G. Dilantha Fernando1 Received: 26 April 2020 / Accepted: 28 August 2020 © Springer Nature B.V. 2020
Abstract Blackleg, which is caused by the fungus Leptosphaeria maculans (L. maculans), is a major disease of canola in western Canada and worldwide. Long-term use of one source of resistance could cause the breakdown of its effectiveness. Therefore, appropriate use of R genes is very important, and knowledge about the distribution of avirulence genes is a prerequisite for effectively deploying resistance. Of the 14 avirulence genes identified in L. maculans, AvrLm5 and AvrLm9 were recognized as the two alleles of the same gene based on two single nucleotide polymorphisms, C 85T and G 164A/C. In this study, a specific marker was developed to identify AvrLm5 and AvrLm9 based on two single nucleotide polymorphisms, C 85T and G 164A/C, which are responsible for the function of AvrLm9. The specific marker can be used to discriminate the AvrLm9 from avrLm9 accurately in L. maculans isolates, which is consistent with inoculation tests in isolates without AvrLm4-7. This specific marker was used to screen 1229 isolates collected from fields in the years 2014 through 2016 in Manitoba. From 68 to 84% of the isolates were found to contain the AvrLm9 allele; while 4–7% of them were avirulent on the variety Goéland with Rlm9 loci. Furthermore, no isolates having both AvrLm9 and AvrLm7 were detected using a cotyledon test, while 67% to 84% of isolates contained both avirulence genes via PCR detection, implying suppression of AvrLm9 by AvrLm7. In addition, avirulence gene profiles of the other 10 avirulence alleles were examined with the 1229 isolates using cotyledon tests or PCR amplifications. Taken together, this research enables the fast identification of AvrLm5/9, provides the Avr genes’ landscape of western Canada and elaborates the relationship between AvrLm9 and AvrLm7 using isolates from grower fields. Keywords Brassica napus · Leptosphaeria maculans · Avirulence gene · AvrLm4-7 · AvrLm9
Introduction Blackleg is a major disease of canola [oilseed rape, Brassica napus (B. napus)] in many regions including North America, Australia, and Europe, causing significant economic losses each year [1]. It is mainly caused by the fungus Leptosphaeria maculans (L. maculans), which can colonize cotyledons, leaves, stems and pods. Stem cankers caused by L. maculans occur most frequently and result in serious yield Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11033-020-05779-8) contains supplementary material, which is available to authorized users. * W. G. Dilantha Fernando [email protected] 1
Department of Plant Science, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
loss. Resistant varieties, fungicide applic
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