| Tomato yellow leaf curl virus disease is caused by Tomato yellow leaf curl virus(TYLCV),transmitted by Bemisia tabaci in the wild and has become one of the most serious diseases in tomato production in China.Tomato yellow leaf curl virus has a bad effect on yield and quality of tomato and is difficult to control as it has a strong epidemic,heavy damage and rapid spread.Currently,using chemical pesticides and planting resistant varieties are main measures in controlling the disease.However,it has been found that the effect of chemical pesticides on the disease is not ideal,and extensive use of chemical pesticides poses a risk of pesticide residues.Soil fungi are able to produce metabolites with various biological activities and play an important ecological role in the natural world.Therefore,it has received widespread attention and made great progress worldwide.However,there are few studies on Alternaria alternata metabolites inducing yellow leaf curl in tomato plants.Taishan strain of Alternaria alternata(TS001)was isolated and collected by laboratory previously and its promoting effect on plant growth had been proved.In this study,the effects of TS001 on tomato growth and its control efficacy against tomato yellow leaf curl virus were investigated.The results of the study were summarized as follows:1.Seeds of cucumber,corn,tomato and radish treated with 1 mg/L crude metabolites from TS001 could significantly increase root length and root hair number when compared to control group.The germination rate and emergence rate of different varieties of tomato were all above 90% after treated with 1 mg/L crude metabolite of TS001,which was not significantly different from the control group.Meanwhile,the inhibition rate of germination and emergence of several treated tomatoes were negative,indicating that TS001 had a certain promoting effect on tomato.Therefore,spraying TS001 on tomatoes was safe,and had a certain role in promoting the growth of tomato plants,which could reduce the sensitivity of tomato plants to a certain extent,thereby increasing the yield and quality of tomato.2.Field trials demonstrated that TS001 significantly reduced the incidence of tomato yellow leaf curl virus and exhibited remarkable control efficacy.The relative control effects of 1 mg/L,2 mg/L,and 4 mg/L were 41.84%,61.71%,and 75.18% respectively.Control efficacy was the highest when TS001 at 4 mg/L,and there was a significant difference between each treatment and untreated controls.In addition,the height of tomato plants treated with TS001 was significantly higher than that of the control group,and the 4 mg/L treatment was as high as 147.42 cm,which was an increase of 31.47% compared with the control group(112.13 cm).Compared with the pre-administration,4 mg/L,2 mg/L,and 1 mg/L treatments had 36.81 cm,25.13 cm,and 14.54 cm higher plant height than the control.It showed that TS001 could improve the growth of tomato,and reduced the infection of virus effectively.3.miRNA sequencing was conducted on the leaves of tomato plants with yellow leaf curling and shrinkage collected from greenhouses in Fangcun,Shandong Province.Tomato yellow leaf curl virus(TYLCV)and tomato chlorotic viruses were detected in the samples.Tomato chlorosis virus(ToCV),with tomato yellow leaf curl virus accounting for 3.21%.The PCR-identified individual tomato yellow leaf curl virus infection rate was about 53%.Tomatoes treated with TS001 significant influenced the activity of enzymes related to disease resistance.The activity of POD and PPO reached the highest value at 7 days after application of TS001.The maximum values of the 4 mg/L treatment group reached 251.22U/(min·g FW)and 2.62 U/g,which were 1.42 and 1.56 times as much as control group respectively.The experiments showed that TS001 could induce the activity of POD,PPO and SOD in tomato plants.The chlorophyll content of susceptible plants treated with TS001 was significantly higher than that of the control group,and the photosynthetic rate of the plants was enhanced,thereby increasing the yield of the tomato plants.The content of MDA in the treatment group was lower than that in the control group,indicating that the ability of self-regulation and anti-lipid peroxidation of tomato plants was enhanced after spraying TS001.The results showed that the TS001 was able to induce defense enzyme activities in plants to prevent viral diseases.The trial initially demonstrated that the TS001 could promote crop growth,enhance plant disease resistance and stress resistance to some extent. |
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