The Applicaton Of Endophytic Fungi In Reducing The Content Of Heavy Metals In Tobacco

Endophytic fungi play import roles in plant resistance to biotic stress and abiotic stress. Soil heavy metals (HM) contamination is one of the most serious environmental problems in China. This thesis mainly studies the application of the endophytic fungi of tobacco in reducing the content of HM in tobacco, the main contents include: optimization of solid-state fermentation medium for heavy metal-resistance fungal endophyte of tobacco; the effect of mierobial on tobacco HM contents; the influence of chemical fertilizer to fungal endophytic fertilizer in reducing HM of tobacco during tobacco production, the influence of fungal endophytic fertilizer to tobacco disease-resistance to black shank caused by Phytophthora nicotianae.(1) The effect of fungal endophytic agents on tobacco HM contentIn pot tests, tobacco was treated with heavy metal in two methods including the single cadmium stress (5mg/kg) and three kinds of heavy metal stress which were composed of arsenic (4mg/kg), cadmium (5mg/kg) and lead (200mg/kg). The results showed that the HM contents in tobacco leaves were reduced in different degree when application of fungal endophytic agents. Under a single cadmium stresses, tobacco treated by seven fungal endophytic agents:YCEF005, YCEF053, YCEF191, YCEF193, NYN8C05, NYN8G01, NYN771C06, the content of HM Cd2+was reduced by39.10%,35.65%,25.98%,39.10%,26.28%,18.83%and21.85%, respectively. Under the three kinds of HM stress, tobacco treated by seven fungal endophytic agentss, the arsenic, cadmium and lead contents in tobacco leaves were reduced. The rate of arsenic, cadmium and lead contents reducing were highest in YCEF005, YCEF191and NYN771C06treatment by36.07%,50.56%and53.86%, respectively.Under the field trials condition, the fungal endophytic agents can reduce arsenic, cadmium and lead contents in tobacco leaves. The rate of HM reducing was achieved better in YCEF005, YCEF053fungal endophytic agents than that of YCEF191, YCEF193in field trials. The extent of reducing the HM content was different in different geographical field. The geographical factor on fungal endophytic agents has remarkable effect on the contents of cadmium and lead but without significant effect on the content of arsenic. The effects of HM reducing by fungal endophytic agents were more significant in the soils with higher HM. The leaves factor on fungal endophytic agents has remarkable effect on the content of lead but without significant effects on the content of arsenic and cadmium The varieties factor on fungal endophytic fertilize has no significant effect on the content of three kinds of HM.(2) The influence of endophytic fungi on tobacco disease resistanceAfter inoculation of Phytophthora nicotianae, tobacco disease symptom reduced significantly in the treatment with YCEF005, YCEF053, and the relative disease index were0.81,0.75, respectively, improve the disease resistance to Phytophthora nicotianae.(3) Optimization of solid-state fermentation medium for HM-resistance endophytic fungi of tobacco.For tobacco endophytic fungi Fusarium sp. YCEF005and Prenochaeta sp. YCEF053, the composition of fermentation substrates were optimized through single-factor experiment and orthogonal experimental design. For YCEF005:50%Wheat bran,10%Bean cake powder,20%Rice bran,20%Corn flour. For YCEF053:60%Wheat bran,10%Bean cake powder,10%Rice bran,20%Corn flour. Preliminary screening of additional nutritions:carbon source, nitrogen source, phosphate and metal ions were conducted by single-factor experiment on the basis of the fermentation substrates. The solid-state fermentation model of endophytic fungi was established by using the data of uniform design as training sample of ANN. Additional nutritions of solid-state fermentation substrates and inoculation amount were optimized by genetic algorithm (GA). For YCEF005(/kg):Sucrose12.96g, Peptone12.70g, NH4NO34.00g, KH2PO41.50g, MgSO40.48g, CaSO410.00g, water content500g inoculation amount240mL. For YCEF053(/kg):Sucrose13.37g, Peptone14.02g,NaNO33.85g,KH2PO41.23g, MgSO40.52g, CaSO410.89g, water content480g, inoculation amount200mL.(4) The influence of chemical fertilizers on the effect of fungal endophytic agentsBy Plackett-Burman test design, the influence of chemical fertilizers on the effect of HM reducing in tobacco by fungal endophytic agents was investigated. The results showed that four kinds of agents, NH4NO3, K2SO4, KNO3and NaNO3, have inhibitory effect to YCEF005in various degree, the order was NH4NO3>KNO3>K2SO4> NaNO3. While three fertilizer, H2NCONH2, KH2PO4and (NH4)2SO4, have promotion effect to YCEF005in various degree, the order was:NH4NO3> H2NCONH2>(NH4)2SO4. But, no one have a significant impact on the growth of YCEF005.