| Verticillium wilt of strawberry,caused by Verticillium dahliae,is a serious soil-borne disease of strawberry.The compost extracts extracted from the compost can be used as an efficient liquid fertilizer.In this paper,the inhibitory effect of compost extracts on Verticillium dahliae was studied,and the optimum extraction conditions were determined.The control effect of compost extracts on strawberry verticillium wilt was studied by greenhouse pot experiments.Finally,the biocontrol mechanisms of compost extracts were discussed.According to the mycelial growth inhibition test and conidia germination inhibition test results,the compost extracts extracted under aeration and non aeration conditions had obvious inhibitory effect on Verticillium dahliae,the inhibitory rate of 16 d reached 82.84% and 86.99%,the inhibition rate of conidia germination of 24 h reached 61.34% and 68.90%,respectively.The results of single factor experiment showed that the aerated compost extracts was better than the non-aerated compost extracts.The effects of extracting time,extracting temperature and ratio of compost to water on the inhibitory rate of compost extract were investigated under aeration conditions.The results showed that the extracting time had the most significant effect on inhibitory rate,and the best extracting conditions was the following: extracting temperature of 30?,extracting time of two days and compost to water ratio of 1:6.The effects of different dilutions of compost extracts on the growth of strawberry were studied by greenhouse pot experiments.In terms of disease control,when strawberry plants were treated with 3 times diluted compost extracts,at 90 d after inoculation,the disease index was 46.67,and the biocontrol effect reached the maximum value of 35.63%.In promoting plant growth,when strawberry plants were treated with 3 times diluted compost extracts,at 90 d after inoculation,the indicators were superior to other treatments,the plant height was 15.40 cm,the stem diameter was 19.43 mm,the petiole length was 9.68 cm,the petiole diameter was 3.36 mm,the leafarea was 30.36 cm2,the green degree of leaf was 60.45,the dry weight of shoot was 3.30 g,and the dry weight of root was 2.41 g.Compared with the control,the corresponding increase ratio were respectively 30.51%,34.19%,39.28%,23.99%,43.75%,14.27%,25.26%,respectively.In conclusion,3times diluted compost extracts had the best effect.The biocontrol mechanisms of compost extracts were studied.Compared with the original compost extracts,the inhibitory rate of heat-sterilized and filter-sterilized compost extracts after incubation of 16 days decreased by about 85% and 80%,and the inhibition rate of conidia germination after incubation of 24 h decreased by about 55% and 25%,respectively.It was proved that the competitive effect of the microorganisms in the compost extracts was the important reason of its inhibitory effect.217 strains of microbes were isolated from compost extracts.13 antagonistic strains of Verticillium dahliae were screened out by preliminary screening.Finally,G19 strain was proved to have the strongest inhibitory effect,and was identified as Streptomyces griseorubens.When strawberry plants were stimulated by the pathogen,the activities of peroxidase(POD)and polyphenol oxidase(PPO)in the leaves of strawberry increased significantly after applying compost extracts,and showed a trend of increasing first and then decreasing during 11 days.On the 5th day,the activities of POD and PPO reached the maximum values of 455.9 U/gˇmin and 257.6 U/gˇmin,respectively.The content of malondialdehyde(MDA)in the leaves decreased significantly after applying compost extracts.On the 11 th day,the MDA content decreased by 33.03% compared with that of water treatment.These results indicated that the competitive effect of the microorganisms,antagonistic effect and the promoting effect of compost extracts on the induction of plant disease resistance result in biocontrol effect of compost extracts on strawberry verticillium wilt. |
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