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Title: The FonSIX6 gene acts as an avirulence effector in the Fusarium oxysporum f. sp. niveum - watermelon pathosystem

Author
item NIU, XIAOWEI - Zhejiang Academy Of Agricultural Sciences
item ZHAO, XIAOQIANG - Zhejiang Academy Of Agricultural Sciences
item Ling, Kai-Shu
item Levi, Amnon
item SUN, YUYAN - Zhejiang Academy Of Agricultural Sciences
item FAN, MIN - Zhejiang Academy Of Agricultural Sciences

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/27/2016
Publication Date: 6/20/2016
Citation: Niu, X., Zhao, X., Ling, K., Levi, A., Sun, Y., Fan, M. 2016. The FonSIX6 gene acts as an avirulence effector in the Fusarium oxysporum f. sp. niveum - watermelon pathosystem. Scientific Reports. 6:28146.

Interpretive Summary: Fusarium wilt is a serious disease on watermelon and a number of other vegetable crops. In plant and pathogen interaction, a specific pathogen gene that is involved in causing the disease on a susceptible cultivar could also be the gene that triggers a resistance response (effector) in a resistant cultivar. Identification and functional characterization of a gene(s) that is involved in virulence or non-virulence of a pathogen will likely facilitate the process in finding a resistance gene in the host plant. In the present study, ARS scientists at the U.S. Vegetable Laboratory in collaboration with scientists at the Zhejiang Academy of Agricultural Sciences in China identified for the first time the presence of a candidate gene in the Fusarium pathogen and demonstrated its protein was able to trigger a resistance response in watermelon. The identification and characterization of the effector gene in the Fusarium pathogen will likely facilitate breeding efforts to develop watermelon cultivars with a durable resistance to fusarium wilt.

Technical Abstract: There are three generally accepted Fusarium oxysporum f. sp. niveum (Fon) physiological races (0, 1, and 2) that infect watermelon (Citrullus lanatus). Among them, race 1 is the most prevalent on watermelon throughout the world, while race 2 is highly aggressive to all commercial watermelon cultivars and hybrids. The avirulence genes of Fon races affecting watermelon are currently unknown. In the present study, the SIX (secreted in xylem) protein 6 was identified in Fon races 0 and 1, but not in the more virulent Fon race 2. A knock-out mutant 'FonSIX6 was constructed in the Fon race 1 to disrupt the FonSIX6 gene function. Disrupting the FonSIX6 gene in Fon race 1 did not affect fungal sporulation or growth rate, but significantly enhanced Fon virulence in watermelon. Complementation of the wild-type race 2 with FonSIX6 reduced its virulence, confirming that FonSIX6 is an AVR gene. Identifying FonSix6 as an avirulence factor sets the first step to elucidate the mechanisms of Fon virulence and resistance in watermelon.