三七连作土壤浸提液对其根腐病菌的化感效应

采用甲醇、乙酸乙酯和水分别按液土比3∶1、6∶1和9∶1对三七连作土壤进行浸提,研究其浸提液对三七根腐病菌生长和种群数量的影响。结果表明: 平板培养72 h后,甲醇、乙酸乙酯和水浸提液对尖镰孢菌和腐皮镰孢菌的菌丝生长均表现为化感促进,其中,甲醇和乙酸乙酯浸提液对尖镰孢菌的化感效应指数为14.0%～19.8%和16.2%～20.2%,高于水浸提液的8.9%～14.2%,且不同浸提比例之间差异不显著;而甲醇浸提液对链格孢菌菌丝生长表现为化感抑制,且抑制效应在浸提比例为3∶1时最强,达到-33.2%～-38.5%,乙酸乙酯和水浸提液对链格孢菌菌丝生长无显著影响。土壤培养4周后,甲醇、乙酸乙酯和水浸提液均能增加土壤中尖镰孢菌的数量,其中,水浸提液的增加效应最强,达到每克干土3.49×10⁶～9.56×10⁶拷贝数,高于甲醇(每克干土1.68×10⁴～6.73×10⁴拷贝数)和乙酸乙酯浸提液(每克干土1.77×10⁴～3.72×10⁴拷贝数),且这种增加效应随浸提比例的增加逐渐减弱;水浸提液和低浸提比例的甲醇提取液均能增加土壤中腐皮镰孢菌的数量,而重茬土壤浸提液对链格孢菌的数量影响不显著。因此,三七连作土壤浸提液对根腐病菌如尖镰孢菌和腐皮镰孢菌均表现出明显的化感促进效应,这可能是再植三七易发生根腐病等土传病害的原因之一。

Allelopathic effect of extracts from Panax notoginseng mono-cropped soil on its root rot pathogens

Methanol, ethyl acetate, and water were used to extract the continuous cropping soils of Panax notoginseng, with the solution/soil ratios of 3:1, 6:1, and 9:1. We investigated the effects of those soil extracts on the growth and population of root-rot pathogens of P. notoginseng. Results showed that the methanol, ethyl acetate and water extracts all promoted mycelial growth of Fusarium oxysporum and Fusarium solani after 72 h of plate culture. The response indices of methanol and ethyl acetate extracts on the growth of F. oxysporum were 14.0%-19.8% and 16.2%-20.2%, being higher than that of water extract (8.9%-14.2%), but without significant difference between diffe-rent extraction ratios. However, methanol extract inhibited the mycelial growth of Alternaria spp. The inhibitory effect was highest at the extraction ratio of 3:1, reaching -33.2% to -38.5%. Ethyl acetate and water extracts did not affect the mycelial growth of Alternaria spp. After four weeks of soil culture, methanol, ethyl acetate and water extracts all increased the F. oxysporum populations. The positive effect of water extract was higher than that of methanol (1.68×10⁴-6.73×10⁴ copies·g^-1 dry soil) and ethyl acetate (1.77×10⁴-3.72×10⁴ copies·g^-1 dry soil) extracts, being 3.49×10⁶-9.56×10⁶ copies·g^-1 dry soil. This increment was weakened along with the increase of extraction ratio. Both water extract and methanol extract with low extraction ratio could increase the F. solani populations, while there were no significant effects of methanol, ethyl acetate and water extracts on the population of Alternaria spp. Therefore, the extracts from continuous P. notoginseng cropping soil showed allopathically promoting effects on the growth and population of root-rot pathogens, F. oxysporum and F. solani, which may be one of the reasons for the occurrence of root rot and other soil-borne diseases in replanted P. notoginseng gardens.