Analysis of soil bacterial diversity under cucumber-celery intercropping and its influence on cucumber Fusarium wilt

Cucumber wilt is a soil disease that is highly prevalent in the production and cultivation of cucumber. The disease is highly difficult to prevent and cure. A number of studies have shown that intercropping was one of the most effective methods of reducing the occurrence of plant soil diseases. Also celery has been proven to have high allelopathy. To explore the application of allelopathic effects of celery on cucumber fusarium wilt control, we conducted cucumber and celery intercropping experiment. In the experiment, three planting patterns were set, which were cucumber-celery intercropping, celery monocropping and cucumber monocropping. The cucumber-celery intercropping pattern was regarded as treatment group and monocropping patterns of celery and cucumber regarded as the control group. The Miseq platform of Illumina Company was used to analyze 16S rDNA bacterial community diversity through high-throughput sequencing to discuss the influence of cucumber-celery intercropping on cucumber soil bacterial diversity. Cucumber was planted in soil from different planting patterns and inoculated with Fusarium oxysporium f.sp.cucumerinum (Foc) in the pot experiment to investigate the control effect of cucumber-celery intercropping on cucumber fusarium wilt. The 16S rDNA sequencing results showed that total bacterial species amount and community diversity were highest in soil under cucumber-celery intercropping, which significantly enhanced observed bacteria species index, Shannon index and Chao1 index (P < 0.05). Beta diversity clustering analysis showed there existed a difference in environmental community species between soil from cucumber-celery intercropping and mono-cropped cucumber or celery. Moreover, 15 bacterial phyla were detected. Proteobacteria, which was followed by Acidobacteria and Actinobacteria, had a distinct advantage (35.7%-38.0%). Then the proportion of bacterial species derived from cucumber-celery intercropped soil was highest (98.63%). About 428 bacterial genera were detected with 5 dominant bacterial genera, which were GP6, GP16, GP4, Gemmatimonas and Arthrobacter. Arthrobacter, Rhodoplanes, Sphingomonas and Blastococcus were dominant bacteria genera in cucumber-celery inter-cropped soil. The 4 genera demonstrated that cucumber and celery intercropping enriched the diversity of bacterial communities compared with monocropped celery or cucumber. The results of fusarium wilt inoculation experiment of cucumber suggested that the control efficiency of cucumber-celery intercropping to cucumber fusarium wilt reached 57.03%-63.54% and 66.95%-72.15% relative to monocroped celery and cucumber, respectively. Therefore cucumber-celery intercropping increased the diversity of bacterial communities, and reduced incidence rate of cucumber fusarium wilt. This was of scientific interest for the prevention and control of soil borne diseases.