西芹鲜根浸提液作用后黄瓜枯萎病菌弱毒菌株的筛选

Screening of virulence-attenuated strains for Fusarium oxysporum f. sp. cucumerinum after treatment with parsley fresh root extract

结合室内化感抑菌作用试验和温室人工接菌盆栽试验,研究了西芹鲜根浸提液连续处理对黄瓜枯萎病菌菌丝生长的影响及病菌致病力的变化。结果表明,在连续5代浸提液作用下,50 mg.mL 1的西芹鲜根丙酮、乙醇浸提液与其对照相比,显著抑制了黄瓜枯萎病菌菌落的生长,表现为化感抑制作用。50 mg.mL 1的西芹鲜根蒸馏水浸提液处理只有在第3代培养过程中,对菌落生长表现为化感抑制作用,其他几代则既有抑制作用又有促进作用。温室人工接菌各代不同处理的黄瓜枯萎病菌进行菌株致病力测定,并于1周开始发病后调查病情。结果显示,连续5代继代培养后接种过程中,西芹鲜根丙酮、乙醇、蒸馏水浸提液处理较其对照致病力降低,表现为浸提液对黄瓜枯萎病菌毒力的致弱作用;且随继代培养代数的增加,病菌的致病力表现为逐渐降低。继代培养至第5代时,丙酮浸提液处理的致病力为0,表现为致弱作用最强。试验通过西芹鲜根浸提液的连续处理筛选到了黄瓜枯萎病菌的弱毒菌株。

Previous studies have shown that parsley extracts from fresh roots,rotten roots,rhizospheric soils,rhizospheric rotten soils,seed or volatiles have allelopathic effects on Fusarium oxysporium f.sp.cucumerinum（Foc）.Different parsley extracts had different allelopathic effects on Foc and were related to extract concentration and action time.In terms of time-invariance,allelopathic effects increased with increasing concentration of different extracts.However,in terms of concentration,allelopathic effects weakened with prolonged duration of action of different extracts.Other studies have noted that different extracts（ethanol,acetone and distilled water） of fresh parsley roots inhibit mycelia growth of Foc,reduce the number of pathogenic spores and limit spore germination rate.Did treatment of Foc with successive generations of different parsley fresh root extracts always resulted in allelopathic inhibition of pathogens？ Did any such allelopathic inhibition influence Foc virulence？ Based on the above issues,the effect of fresh parsley root extract on Foc growth and pathogenicity were studied in laboratory antifungal experiments and artificially inoculated potted cucumbers in greenhouse conditions.In the first part of the study,Fusarium colonies were treated with 50 mg.mL 1 of fresh parsley root extracts respectively in acetone,ethanol,distilled water and the corresponding control,and colony diameters assessed for 5 generations.Compared with the control,both acetone and ethanol extracts had lower colony diameter after continuous assessment for 5 generations.Aqueous extracts had lower colony diameters than the control only in the 3 rd generation.Both inhibition and promotion of allelopathy on Foc were expressed in the other generations.In the second part of the study,each generation of treated Foc strains was used to inoculate cucumber in order to determine their pathogenicity.After 7 days,disease index was assessed on the seedlings.The results showed that fresh parsley root acetone,ethanol and distilled water extract treatments had lower disease index than the control after 5 continuous generations of inoculation.It also had attenuation effect on Foc virulence.Foc virulence gradually decreased with increasing subculture generation.By the time when the 5 th generation strain was inoculated,disease index of acetone extract dropped to 0.It also had the greatest attenuation of virulence and colonial morphology change.Colony color changed from white to lavender and colony density dropped from dense to sparse.The study screened virulence-attenuated Foc strain through fresh parsley root extracts under continuous processing.