pH值对香蕉枯萎病菌4号生理小种生长的影响

【背景】香蕉枯萎病菌4号生理小种(镰刀菌)是香蕉产业的致命威胁。已有研究表明土壤pH值越高,香蕉枯萎病发病率越低,但是现有pH值对镰刀菌影响的研究大都是用强酸强碱调节pH值,pH值没有缓冲体系保护,而且尚未检测试验终点时介质的pH值。此外,关于pH值对香蕉枯萎病菌4号生理小种(Foc4)影响的研究尚不系统,难以用于指导生产实践。【目的】为系统地了解土壤酸碱度对Foc4生长的影响。【方法】在pH 3.0-11.0之间设定9个pH值梯度,模拟酸性到碱性土壤pH值条件,于室内培养条件下系统研究pH值对Foc4生长、产孢、孢子萌发的影响及其生长过程对环境pH值的影响。【结果】弱酸性至中性环境(pH 5.0-7.0)最适宜于香蕉枯萎病菌的生长、产孢和孢子萌发。弱碱性处理(pH8.0和pH9.0)孢子平均萌发率较弱酸性环境处理(pH5.0和pH6.0)下降了73.1%。与pH 6.0酸性处理相比,pH 8.0和pH 9.0处理的产孢量分别下降了52.3%和68.1%。【结论】香蕉枯萎病菌Foc4生长和萌发过程会产酸,但是在缓冲体系液体培养基中,除了pH 9.0和pH10.0处理终点培养液pH值分别下降了0.34和0.27个单位外,其它处理起始和终点的pH值无差异。说明在缓冲体系液体培养基中的研究结果可以反映环境pH值对Foc4生长和萌发的影响。在作物可以生长的pH值范围内(pH5.0-9.0),碱性和微碱性条件(pH8.0-9.0)能明显抑制Foc4生长、产孢和孢子萌发。

Effect of pH on the growth of Fusarium oxysporum f. sp. cubense race 4 of banana

Background] Fusarium oxysporum f. sp. cubense race 4 (Foc4) has been a life-threatening disease to banana production. Present studies have shown that soil pH is negatively correlated to the onset of banana wilt disease. However, most studies of influence of the pH on growth of Foc4 of banana were done under the condition of the pH being adjusted with strong acid and alkali, without tested the terminal pH of the test medium. In fact, the investigation of the pH on Foc4 is not systematic and the results of the study are not practice to guide farmers to remedy the Foc4 disease by modifying the soil pH. Objective] to study the effect of pH on growth, sporulation and spore germination of Foc4 as well as the side effect of growth, sporulation and spore germination of Foc4 on the environmental pH throughly. Methods] Laboratory incubations with 9 pH treatments from pH 3.0 to pH 11.0 were applied in the study. Results] The most suitable condition for growth, sporulation and spore germination of the Foc4 is weak acid to neutral environment, being pH 5.0 to 7.0. The average germination rate of spores in weakly alkaline environment (pH 8.0 and pH 9.0) was decreased by 73.1% compared to that in weakly acidic environment (pH 5.0 and pH 6.0). Compared with the acid treatment under pH 6.0, the sporulation rate under pH 8.0 and pH 9.0 decreased by 52.3% and 68.1%, respectively. Conclusion] The growth and germination of Foc4 is able to secrete acid. However, terminal pH of the liquid medium has been stable when pH buffer system is used in the medium to culture the Foc4, except for treatment of pH 9.0 and pH 10.0. The terminal pH of the treatment of pH 9.0 and pH 10.0 only decreased by 0.34 and 0.27 units respectively. The results indicated that the reliable results of the effect of pH on the Foc4 growth and germination should be under the pH buffer system liquid medium. Within the pH range where the crop can grow (pH 5.0?9.0), alkaline and slightly alkaline conditions (pH 8.0?9.0) are capable to inhibit the growth, sporulation and spore germination of Foc4 significantly.