JIA-2018-09

2048 ZHENG Na et al. Journal of Integrative Agriculture 2018, 17(9): 2042–2053 be equal to or over 5×10 6 conidia mL –1 . 3.4 Conidia of an isolated F. solani alone are able to be virulent to soybean To our best knowledge, the virulence of Fusarium to plants is usually caused by the secreted cell degrading enzymes (Cooper et al . 1998; Jayasinghe et al . 2004; Paccanaro et al . 2017) and toxins such as fusaric acid, FvTox1, T-2 toxin, and endo-xylarases (Brito et al . 2006; Brar et al . 2011), and no studies were reported that conidia of Fusarium underlies virulence to plants alone so far. Truly, for almost L A B C D E F G K J H I Fungus Isolate (#) Virulence PI 437654 Zhonghuang 13 Fusarium oxysporum 2 Vir Vir 3 Vir Vir 5 Vir Vir 8 Vir Vir 9 Vir Vir 14 Vir Vir 15 Vir Vir 17 Vir Vir Fusarium solani 4 Vir Vir Fusarium equiseti 6 Vir Vir 7 Vir Vir 10 Vir Vir 11 Vir Vir 16 Vir Vir 18 Avir Vir Fusarium commune 12 Vir Vir 13 Vir Vir Fig. 4 Virulence of Fusarium spp. isolated from soybeans. A, symptoms of roots and stem base at 5 days post infection with (left) and without (right) infection of Fusarium , respectively. B and C, wilting of seedlings at different degrees at 5 days post infection. D–K, virulence of isolate #18 to soybeans. D–G, PI 437654. H–K, Zhonghuang 13. D, F, H and J, CK. E, G, I and K, infection of conidia cultures of isolate #18. D, E, H and I, 0 day post infection. F, G, J and K, 5 days post infection. L, summary of the virulence of Fusarium spp. isolated to soybean. The conidia culture at the concentration of 1×10 7 conidia mL –1 was used. The Fusarium species is virulent (Vir) to soybean if the soybean seedlings were wilted, while the Fusarium species is avirulent (Avir) to soybean if the soybean seedlings were not wilted, at 5 days post infection. A B H G I C D F E J Fig. 5 Determination of effective concentration of conidia cultures of Fusarium spp. causing wilting of soybean seedlings. Taken together with the results that the conidia cultures at the concentration of 1×10 7 conidia mL –1 caused the wilting of seedlings (Fig. 4), the results show that the conidia cultures at the concentration of equal to or over 5×10 6 conidia mL –1 caused the wilting of seedlings. A–E, 0 day post infection. F–J, 5 days post infection. A and F, CK. B and G, C and H, D and I, and E and J, conidia cultures at the concentration of 5×10 6 , 1×10 6 , 5×10 5 , and 1×10 5 conidia mL –1 , respectively. F. equiseti isolate #11 was used to infect soybean Zhonghuang 13.