Isolation and characterization of phosphate-solubilizing bacteria from rhizosphere of poplar on road verge and their antagonistic potential against various phytopathogens.

BACKGROUND: Phosphate-solubilizing bacteria (PSB) can solubilize insoluble phosphate compounds and improve phosphate availability in soil. Road verges are important in urban landscaping, but the population structure of PSB and their ecological functions in the road verge soil is still unclear. RESULTS: Twenty-one mineral PSB strains and 14 organic PSB strains were isolated from the rhizosphere of poplar on urban road verge. All the mineral PSB strains showed better solubilization to Ca3(PO4)2 than FePO4 or AlPO4. Among them, 7 strains showed high phosphate-solubilizing (PS) activities to Ca3(PO4)2 (150-453 mg/L). All the organic PSB strains displayed weak solubilization to lecithin. 16S rRNA gene-based phylogenetic analysis showed good species diversity of the PSB strains, which belongs to 12 genera: Bacillus, Cedecea, Cellulosimicrobium, Delftia, Ensifer, Paenibacillus, Pantoea, Phyllobacterium, Pseudomonas, Rhizobium, Sinorhizobium and Staphylococcus. Moreover, 8 PSB strains showed various degrees of growth inhibition against 4 plant pathogenic fungi, Fusarium oxysporum S1, F. oxysporum S2, Pythium deliense Meurs Z4, Phomopsis sp. AC1 and a plant pathogenic bacterium, Pectobacterium carotovorum TP1. CONCLUSIONS: The results indicated that these PSB strains could perform multiple ecological functions on road verge. The development and application of bio-agents based on the strains would provide a new strategy for maintaining and improving the ecosystem stability of road verges.

Genetic diversity and genome-wide association analysis of pine wood nematode populations in different regions of China.

Introduction: Pine wilt disease (Bursaphelenchus xylophilus) was recently detected in Liaoning Province, which was previously considered an unfavourable area for B. xylophilus due to its low temperatures. This study aims to compare the reproductivity and genetic variations of B. xylophilus isolates from Liaoning Province and other parts of China to explore their phenotypic and genomic differences. Methods: The samples from Liaoning, Anhui, Hubei, Henan, Zhejiang and Jiangsu were isolated and purified to obtain the strains. The reproductivity of the strains was determined at 15 °C. The genetic structure was analyzed by using SNP molecular markers, and the whole genome association analysis was carried out by integrating SNP information and feculence traits. Results: A reproductivity experiment showed that Liaoning isolates have higher reproductive ability at 15 °C. Subsequent SNP profiling and population differentiation analysis revealed obvious genetic differentiation of Liaoning isolates from other isolates. A genome-wide association study showed that SNPs closely related to low-temperature tolerance were mainly located in GPCR, Acyl-CoA, and Cpn10, which are responsible for adaptation to environmental factors, such as temperature change. Discussion: Pine wood nematodes likely adapted to the climate in Liaoning and maintained a certain reproductive capacity at low temperature via variants of adaptation-related genes. This study provides a theoretical basis for elucidating the prevalence and diffusion status of B. xylophilus in China.