| Popis: |
The deterioration of the soil microbial population and the decline of enzyme activity have been regarded as two key factors in the reduction of watermelon yield in long-term continual watermelon cropping systems.To replicate the watermelon cropping system as much as possible,a surface layer(50—200 mm depth) of an Ultisol was sampled from a 3 year-old continuously cropped upland watermelon site,at the Red Soil Experimental Station,Chinese Academy of Agricultural Sciences,Yongzhou,Hunan Province(N26°45′,E111°53′).Pot experiments were conducted to investigate the effects of the addition of Ceratobasidium stevensii B6 on watermelon(Citrullus lanatus) yield(and the associated soil microflora) to study biological control measures for a long-term continual watermelon cropping system.Three treatments were used a control(A),an inactivated B6 mycelia(B) and an activated B6 mycelia treatment(C).At the harvest stage,the application of living B6 mycelia(Treatment C) significantly reduced the number of soil fungal colony forming units(CFU) by 17%,but the quantity of bacteria and actinomycetes increased by 2.2 and 0.4 fold respectively,compared with the control(A).For the treatment using the activated B6 mycelia(C),the quantity of Fusarium oxysporum(FO) in the soil at the harvest stage decreased by 29.9% and 63.3% compared with the control(A) and the inactivated B6 mycelia(B) respectively.Meanwhile,the activities of soil urease,sucrase and polyphenol oxidase were enhanced by 19.0%,159.0% and 31.3% in treatment C compared with treatment A,respectively.Moreover,the activities of superoxide dismutase and peroxidase in the watermelon leaves also increased by 32.7% and 4.6% when compared with treatment A,respectively.In other words,the activated B6 mycelia significantly induced a systemic resistance of watermelons to the invasion of FO.Furthermore,in contrast with treatment A,root activities in treatment C were increased by 46.2% while the malonaldehyde content(MDA) in the leaves was reduced by 51.4%.Compared with the control(A) and inactivated B6 mycelia(B),the individual fruit weight increased by 44.8% and 40.9% respectively in the treatment where activated B6 mycelia were added.Total yield was also increased by 103.8% and 64.9%,respectively.The soluble sugar content of the fruit likewise was increased by 35.1% and 10.0% for treatment C when compared with the other treatments.Although the differences in the vitamin C concentration of the watermelon fruit between all the treatments was not significant,the quality of the watermelons in treatment C was improved,as evidenced by an increase in the soluble sugar content.These results suggested that the addition of the activated B6 mycelia for improving the soil microenvironment and to increase the watermelon yield has promise,and may be able to be commercially used in the future;hence,further research is required on the mechanisms involved. |
