Screening of Cucumber Fusarium Wilt Bio-Inhibitor: High Sporulation Trichoderma harzianum Mutant Cultured on Moso Bamboo Medium

Cucumber fusarium wilt is a soil-borne disease which causes serious production decrease in cucumber cultivation world widely. Extensive using of chemical pesticides has caused serious environmental pollution and economic losses, therefore, it is particularly urgent to develop efficient, safe and pollution-free biopesticide. In this study, a mutant strain of Trichoderma harzianum cultivated in moso bamboo medium was proved to be an efficient bio-inhibitor of the disease. The mutant strain T. harzianum T334, was obtained by three microwave mutagenesis cycles with an irradiation power of 600 W and irradiation time of 40 s. In contrast to the original strain, the inhibition rate on cucumber fusarium wilt of the strain T334 increased from 63 to 78%. In this work, disk milling pretreatment of moso bamboo has shown significant beneficial effects on both biotransformation and sporulation of T334. Its sporulation reached 3.7 × 109 cfu/g in mushroom bags with 90% bamboo stem powder (pretreated by disk milli), 9.5% bamboo leaf powder and 0.5% wheat bran when the ratio of solid to liquid was 4:6, the inoculum amount was 10%, and the culture temperature was 28°C. These results provide an alternative bioinhibitor for the control of cucumber fusarium wilt, and a potential usage of moso bamboo in the production of microbial pesticide.

Allelopathic Control Effect of Complex Formulation of Compound Microbial Community and Bio-Organic Fertilizer on Cucumber fusarium Wilt

To study the influence of complex formulation of �WoFengKang� compound microbial community and bio-organic fertilizer on allelopathic effect of cucumber fusarium wilt and field growth traits, in this experiment, different indoor treatments were taken to cultivate cucumber fusarium wilt using soil leaching liquor and Cucumis sativus growth index, fusarium wilt disease index were determined, so that allelopathic control effect of different dosages of compound microbial community on cucumber fusarium wilt can be investigated. The results showed that: compared with conventional CK, cucumber fusarium wilt cultured in different soil leaching liquor had smaller diameter. Where, colony diameter in treatment 3 was the smallest, which was 36.72 mm. Compound microbial community had certain allelopathic effect on cucumber fusarium wilt, and inhibition effect was shown with allelopathic effect reaching 27.13~43.91%. The above differently-treated soil was loaded to seedling-raising pot for Cucumis sativus planting. Cucumber fusarium wilt (FOC) was inoculated in the rough leaf stage of Cucumis sativus, thus reducing the disease index of cucumber fusarium wilt with obvious control effect reaching 55.94~72.63%. Where, treatment 3 demonstrated the best effect and allelopathic control effect reached 72.63% after 15d inoculation. The complex formulation of the two promoted vegetative growth of Cucumis sativus, lowered node of the first female flower bud, increased the number of female flowers within 30 nodes, so that 3.25d early flowering and 4.75d delayed seedling raising were achieved. Therefore, application of microbial community amid and after Cucumis sativus field planting has certain allelopathic control effect on cucumber fusarium wilt, which can effectively reduce the incidence of cucumber fusarium wilt and provide a scientific basis for the allelopathic prevention and control of soil-borne diseases in Cucumis sativus.

Rotations with Indian Mustard and Wild Rocket Suppressed Cucumber Fusarium Wilt Disease and Changed Rhizosphere Bacterial Communities

Crop monocropping usually results in an enrichment of soil-borne pathogens in soil. Crop rotation is an environmentally friendly method for controlling soil-borne diseases. Plant rhizosphere microorganisms, especially plant-beneficial microorganisms, play a major role in protecting plants from pathogens, but responses of these microorganisms to crop rotation remain unclear. Here, we evaluated the effects of rotations with Indian mustard (Brassica juncea) and wild rocket (Diplotaxis tenuifolia (L.) DC.) on cucumber Fusarium wilt disease caused by Fusarium oxysporum f.sp. cucumerinum Owen (FOC). Cucumber rhizosphere bacterial community composition was analyzed by high-throughput amplicon sequencing. Bacteria, Pseudomonas spp., 2,4-diacetylphloroglucinol (an antifungal secondary metabolite) producer and FOC abundances were estimated by real-time PCR. Rotations with Indian mustard and wild rocket suppressed cucumber Fusarium wilt disease and cucumber rhizosphere FOC abundance. Crop rotations increased cucumber rhizosphere bacteria, Pseudomonas spp. and 2,4-diacetylphloroglucinol producer abundances. Moreover, crop rotations changed cucumber rhizosphere bacterial community composition and increased bacterial community diversity. However, crop rotations decreased soil inorganic nitrogen content and inhibited cucumber seedling growth. Overall, rotations with Indian mustard and wild rocket suppressed cucumber Fusarium wilt disease, which might be linked to the increased rhizosphere bacterial diversity and abundances of potential plant-beneficial microorganisms (such as Pseudomonas spp. and 2,4-diacetylphloroglucinol producer).