AUTHOR=Elnahal Ahmed S. M. , Li Jinyang , Wang Xiaoxia , Zhou Chenyao , Wen Guohong , Wang Jian , Lindqvist-Kreuze Hannele , Meng Yuling , Shan Weixing 

TITLE=Identification of Natural Resistance Mediated by Recognition of Phytophthora infestans Effector Gene Avr3aEM in Potato

JOURNAL=Frontiers in Plant Science

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.00919

DOI=10.3389/fpls.2020.00919

ISSN=1664-462X

ABSTRACT=<p>Late blight is considered the most renowned devastating potato disease worldwide. Resistance gene (<italic>R</italic>)-based resistance to late blight is the most effective method to inhibit infection by the causal agent <italic>Phytophthora infestans</italic>. However, the limited availability of resistant potato varieties and the rapid loss of <italic>R</italic> resistance, caused by <italic>P. infestans</italic> virulence variability, make disease control rely on fungicide application. We employed an <italic>Agrobacterium tumefaciens</italic>-mediated transient gene expression assay and effector biology approach to understand late blight resistance of Chinese varieties that showed years of promising field performance. We are particularly interested in <italic>PiAvr3a<sup>EM</sup></italic>, the most common virulent allele of <italic>PiAvr3a<sup>KI</sup></italic> that triggers a <italic>R3a</italic>-mediated hypersensitive response (HR) and late blight resistance. Through our significantly improved <italic>A. tumefaciens</italic>-mediated transient gene expression assay in potato using cultured seedlings, we characterized two dominant potato varieties, Qingshu9 and Longshu7, in China by transient expression of <italic>P. infestans</italic> effector genes. Transient expression of 10 known avirulence genes showed that <italic>PiAvr4</italic> and <italic>PiAvr8 (PiAvrsmira2)</italic> could induce HR in Qingshu9, and <italic>PiAvrvnt1.1</italic> in Longshu7, respectively. Our study also indicated that <italic>PiAvr3a<sup>EM</sup></italic> is recognized by these two potato varieties, and is likely involved in their significant field performance of late blight resistance. The identification of natural resistance mediated by <italic>PiAvr3a<sup>EM</sup></italic> recognition in Qingshu9 and Longshu7 will facilitate breeding for improved potato resistance against <italic>P. infestans</italic>.</p>