Allelopathy of the root exudates from different resistant eggplants to verticillium wilt(Verticillium dahliae Kleb.)

Verticillium Wilt is one of the most destructive deceases of eggplant in China.Up to now,the allelochemicals from eggplant root exudates have been found in relation to the outbreak of Verticillium Wilt.However,the relationship between root exudates from different eggplant cultivars and their resistance to Verticillium Wilt has not been determined.Four eggplant cultivars were inoculated with Verticillium Wilt(Verticillium dahliae Kleb.) to assess their resistance to Verticillium Wilt in the present study.The results showed that Solanum tor and S.sis were resistant,Liyuanziqie was tolerant,and Xi′anlvqie susceptible.The variation of main microorganism and Verticillium dahliae in rhizospheric soil,the allelopathy of root exudates to mycelium growth of Verticillium dahliae and the chemical substances of root exudates from eggplant cultivars with different resistance to Verticillium Wilt were investigated in this experiment.The experiment results exhibited that the root exudates of resistant and susceptible types inhibited the mycelium growth of Verticillium dahliae,while the susceptible one promoted the mycelium growth,during the whole incubation period.But the influence was waned gradually with time elapsing.The number of Verticillium dahliae sclerotia in the soils of all cultivars was increased with eggplant growth.The resistant types showed significantly lower population of Verticillium dahliae at each growth stage compared to the susceptible one.These conclusions were consistent with the disease incidence and the disease index of Verticillium wilt in the field.The root exudates of resistant types could not only affect the growth and development of Verticillium dahliae,but also influence Verticillium dahliae indirectly through regulating soil microbial community composition.With the reduction of bacterium,the population of total microorganisms(including bacterium,actinomyces and fungi) in rhizophere decreased,especially Xi′anlvqie.Comparing with the eggplants without inoculation,the population of actinomyces in rhizosphere of Xi′anlvqie phased down,the number of actinomyces decreased by 29.70% in 14 days after inoculation.But the population of actinomyces of resistant and tolerant types increased,the increasing rate showed as S.torS.sisZ.The population of fungi increased in all cultivars during the whole period.As a result,the ratios of B to F and A to F increased gradually until 14 days after inoculation,then decreased,and appeared as S.torS.sisLiyuanziqie Xi′anlvqie.The microorganisms,especially those in the rhizopheric soils,affected the production and transformation of root exduates,and were fed by the root exduates or some component parts.The root exudates of different resistant eggplant cultivars mainly contained Hydrocarbon,Ketone,Ester,Phenol,Phenolic acid,Aldehyde,Alcohol,Quinones and others detected by gas chromatography mass pectrometry.The category and quantity of these chemical substances were in close relation to the resistance to Verticillium wilt.It was inferenced that the resistant types contained some special components,such as Alcohol,Amide,Pyranoid,Fluorene.This may be one of the reasons for the increase of disease resistance.However,the susceptible type exhibited an opposite trend.It comprised more components,i.e.,Phenol,Ester and Phenolic acid.Many of these chemical substances were found to be allelochemical.The change of allelochemicals may be one of the reasons of resistant difference.