Intercropping with marigold promotes soil health and microbial structure to assist in mitigating tobacco bacterial wilt

Abstract

Marigold is reported to have antibacterial activity, and effectively protect crops against soil-borne diseases. However, it is not known whether and how tobacco bacterial wilt (TBW) could be mitigated via intercropping with marigold under field conditions. In this study, a field experiment was performed to measure and compare the occurrence of TBW, the soil chemical properties, and soil microbial composition and diversity between a tobacco-marigold intercropping system and a tobacco monocropping system. At 100 days (d) post-transplantation, the incidence (I) and disease index (DI) for the tobacco-marigold intercropping system were 30.12% and 58.25% lower than that for tobacco monocropping system, respectively. The results showed that Sobs, Shannon and Chao 1 index of soil bacterial communities in the tobacco-marigold intercropping system were 10.34%, 1.41% and 5.13% higher than that in the tobacco monocropping system at 100 d post-transplantation, respectively. It exhibited a higher richness and diversity of soil bacterial communities in the tobacco-marigold intercropping system. The relative abundance of some beneficial genera in tobacco-marigold intercropping system, such as Lysobacter, Burkholderia, Trichoderma, Mortierella, Chaetomium, Penicillium, was 1.50, 1.61, 3.35, 1.67, 4.40 and 4.50 fold higher than that in tobacco monocropping system. The presence of the intercropping system inhibited soil acidification and loss of soil calcium ions. The redundancy analysis (RDA) indicated that soil pH and exchange Ca2+ were the main environmental factors which seemed to influence the bacterial and fungal community. The results from this study provided valuable insight into the possible mechanisms enhancing soil health in the tobacco-marigold intercropping system.

Integrated Biocontrol of Tobacco Bacterial Wilt By Antagonistic Bacteria and Marigold

“…In addition, the soil microbial community varies at different tobacco growth stages. The results of PCA, suggesting different treatments and growth stages could influence soil microbial community structure, which was similar to previous report 20,30 . It was also testified by the Heatmanp, showing the difference of microbial community structure in different treatments.…”

“…In our previous study, B. amyoliquefaciens ZM9 as an efficient biocontrol agent can reduce TBW by producing lipopeptides to against R. solanacearum and changing the tobacco rhizosphere microbial community 13 . Marigold is reported to have antibacterial activity, and effectively reduce the incidence of TBW 18,20 . The application of single biocontrol agent is difficult to perform sustainable and efficient against pathogens of the plant under diverse soil environmental conditions.…”

“…Solanacearum, and soil pH as an environmental factor can regulate the soil physicochemical properties, metabolites and microbial community composition 20,[25][26][27] . Nutrient P has also been reported to meet the need of plant growth and increase the soil microbial diversity, and the increased P supply significantly decreased the relative density of R. Solanacearum 28,29 .…”

“…Marigold also has been reported to successfully suppress R. solanacearum when used as a rotational or intercropping plant under greenhouse conditions 19 . In our previous study, we found that marigold and tobacco intercropping can effectively reduce the incidence of TBW, affect the soil microbial community and soil physicochemical properties 20 . Kamal et al found that the combination of biocontrol agents and resistance inducers could make biocontrol agents better adapt to environment changes and effectively control of bacterial wilt 21 .…”

Integrated Biological Control of Tobacco Bacterial Wilt (<i>Ralstonia solanacearum</i>) and Its Effect on Rhizosphere Microbial Community

“…(5'-GTGCCAGCMGCCGCGGTAA-3') [16] were used to copy the V4 regions of the 16S rRNA gene, while the primers ITS2-2043R (5'-GCTGCGTTCTTCATCGATGC-3') and ITS5-1737F (5'-GGAAGTAAAAGTCGTAACAAGG-3') [36] were used to copy the ITS1 regions of ITS rRNA gene. The Illumina HiSeq platform was used to conduct all PCR reactions and sequencing libraries were constructed with the use of the TruSeq® DNA (Illumina, USA) following the prescribed procedures and approvals.…”