Zheng-Qin Su

Aucklandia lappa Decne is a valuable medicinal herb highly susceptible to root rot, a disease that severely affects its yield and quality. This study provides a comprehensive characterization of the soil ecosystems in A. lappa habitats by integrating biogeochemical and microbial functional analyses. Rhizosphere soil samples were collected from healthy plants growing in loam soil (HLS), root-rot-affected plants growing in loam soil (RRLS), and healthy plants growing in clay soil (HCS) from habitats in the Kaizhou District of Chongqing, China. We analyzed soil physicochemical properties (pH, available nitrogen, potassium, phosphorus, organic matter content, and total carbon), enzyme activities (amylase, cellulase, saccharase, β-glucosidase, β-xylosidase, and laccase), and microbial community structure (using 16S/ITS sequencing). The results demonstrated significant differences in nutrient levels and enzyme activities between healthy and diseased soils, with root-rot-affected soils displaying higher nutrient content and distinct microbial diversity. Specific bacterial (Rahnella) and fungal genera (Trichosporiella, Cyberlindnera, Barnettozyma, and Ilyonectria) were enriched in root-rot-associated soils. This suggests that these microorganisms may participate in rhizosphere ecological responses associated with root rot occurrence, although their roles may include pathogen-associated processes or potential plant adaptation responses. The results demonstrate that root rot occurrence in A. lappa is associated with coordinated changes in rhizosphere nutrient status, enzyme activities, microbial community composition, and predicted functional profiles. However, the observational nature of this study does not allow causal relationships between these changes and root rot development to be established.

Insects and their endosymbionts have a close mutualistic relationship. However, the precise nature of the bacterial endosymbiont-mediated interaction between host plants and whitefly Bemisia tabaci MEAM1 is still unclear. In the present study, six populations of Bemisia tabaci MEAM1 sharing the same genetic background were established by rearing insects for ten generations on different host plants, including poinsettia, cabbage, cotton, tomato, and tobacco, and an additional population was reared on cotton and treated with antibiotics. The physiological and nutritional traits of the insects were found to be dependent on the host plant on which they had been reared. Systematic analysis was conducted on the endosymbiont titers, the amino acid molecules and contents, as well as developmental and oviposition changes in the MEAM1 populations reared on each host plant tested. The results indicate that B. tabaci contained the primary symbiont Portiera and the secondary symbionts Hamiltonella and Rickettsia. In addition, the titer of endosymbiotic bacteria in females is higher than that in males. Among the MEAM1 populations reared on each host plant, the variation pattern of Portiera titer generally corresponded with changes in biological characteristics (body length, weight and fecundity) and AA contents. This suggests that changes in the amino acid contents and biological characteristics of different B. tabaci populations may be due to changes in the Portiera content and the differences in the nutrition of the host plants themselves. Our findings were further confirmed by the reduction in Portiera with antibiotic treatment. The amino acids, body size, body weight, and fecundity of B. tabaci were all reduced with the decrease in the Portiera titer after antibiotic treatment. In summary, our research revealed that host plants can affect the content of symbiotic bacteria, particularly Portiera, and subsequently affect the nutrition (i.e., the essential amino acids content) of host insects, thus changing their biological characteristics.