Arbuscular mycorrhizal fungi improve the growth and disease resistance of the invasive plant Wedelia trilobata.

AIMS: Arbuscular mycorrhizal fungi (AMF) are symbiotic partners of many invasive plants, however, it is still unclear how AMF contribute to traits that are important for the successful invasion of their host and how environmental factors, such as nutrient conditions, influence this. This study was to explore the effects of Glomus versiforme (GV) and Glomus mosseae (GM) on the growth and disease resistance of the invasive plant Wedelia trilobata under different nutrient conditions. METHODS AND RESULTS: We found that GV and GM had higher root colonization rates resulting in faster W. trilobata growth under both low-N and low-P nutrient conditions compared to the normal condition. Also, the colonization of W. trilobata by GV significantly reduced the infection area of the pathogenic fungus Rhizoctonia solani under low-N conditions. CONCLUSIONS: These results demonstrated that AMF can promote the growth and pathogenic defence of W. trilobata in a nutrient-poor environment, which might contribute to their successful invasion into certain type of habitats. SIGNIFICANCE AND IMPACT OF THE STUDY: In this study, we report for the first time that AMF can promote growth and disease resistance of W. trilobata under nutrient-poor environment, which contribute to a better understanding of plant invasion.

Wickerhamiella slavikovae sp. nov. and Wickerhamiella goesii sp. nov., two yeast species isolated from natural substrates.

Two novel yeast species were isolated during three independent studies of yeasts associated with natural substrates in Brazil and Taiwan. Analysis of the sequences of the D1/D2 domains of the large subunit rRNA gene showed that these novel species belong to the Wickerhamiella clade. The first was isolated from freshwater and a leaf of sugar cane (Saccharum officinarum) in Brazil and from leaves of Wedelia biflora in Taiwan. Described here as Wickerhamiella slavikovae sp. nov., it differs by 56 nucleotide substitutions and 19 gaps in the D1/D2 region of the large subunit rRNA gene from Candida sorbophila, the least divergent species. The second species, named Wickerhamiella goesii sp. nov., was isolated from leaves and the rhizosphere of sugar cane collected in Rio de Janeiro, Brazil. The species differs by 54 nucleotide substitutions and nine gaps in the D1/D2 domains from Candida drosophilae, its least divergent relative. The type strains are Wickerhamiella slavikovae sp. nov. IMUFRJ 52096(T) (= CBS 12417(T) = DBVPG 8032(T)) and Wickerhamiella goesii sp. nov. IMUFRJ 52102(T) (= CBS 12419(T) = DBVPG 8034(T)).

Microbial community overlap between the phyllosphere and rhizosphere of three plants from Yongxing Island, South China Sea.

Phyllosphere and rhizosphere are unique and wide-ranging habitats that harbor various microbial communities, which influence plant growth and health, and the productivity of the ecosystems. In this study, we characterized the shared microbiome of the phyllosphere and rhizosphere among three plants (Ipomoea pes-caprae, Wedelia chinensis, and Cocos nucifera), to obtain an insight into the relationships between bacteria (including diazotrophic bacteria) and fungi, present on these host plants. Quantitative PCR showed that the abundances of the microbiome in the soil samples were significantly higher than those in the phyllosphere samples, though there was an extremely low abundance of fungi in bulk soil. High-throughput sequencing showed that the alpha-diversity of bacteria and fungi was higher in the rhizosphere than the phyllosphere samples associated with the same plant, while there was no obvious shift in the alpha-diversity of diazotrophic communities between all the tested phyllosphere and soil samples. Results of the microbial composition showed that sample-specific bacteria and fungi were found among the phyllosphere and rhizosphere of the different host plants. About 10%-27% of bacteria, including diazotrophs, and fungi overlapped between the phyllosphere and the rhizosphere of these host plants. No significant difference in microbial community structure was found among the tested rhizosphere samples, and soil properties had a higher influence on the soil microbial community structures than the host plant species.

[Induction and in vitro culture of Wedelia trilobata hairy roots].

To study the possibilities for improvement of the ornamental character and production of secondary metabolites by using Wedelia trilobata hairy roots, we investigated the induction of W. trilobata L. hairy roots and its consumption changes of carbon resource, nitrogen resource, phosphate and calcium in the medium during liquid culture. The results showed that hairy roots could be incited from the cut edges of leaf explants 7 days after inoculation with Agrobacterium rhizogenes ATCC15834 and could have an autonomous growth on the medium without phytohormones. The PCR amplification showed that rol genes of Ri plasmid of A. rhizogenes was integrated and expressed into the genome of transformed hairy roots. The hairy root line grew very slowly in 0-7 days, very fast from 7 to 21 days. During the liquid culture of hairy roots, sucrose, NO3(-)-N, PO4(3-) and Ca2+ in the medium could be gradually absorbed and utilized with time. The content of NO3(-)-N in the medium was 5.8% of the initial amount at day 7, while sucrose content was about 50% of the initial amount. At day 35, the NO3(-)-N and sucrose content in the medium was 1.82% and 3.39% of the initial amount, respectively. In combination with Ca2+ consumption, PO4(3-) of the medium was rapidly absorbed and utilized. At day 7, the content of PO4(3-) in the spent medium was only 1.76% of the initial amount; but even at day 35, the content of Ca2+ in the spent medium was still 61.3% of the initial amount. The results presented here had provided the possibilities on improvement the ornamental character and how to prepare optimum medium for large scale cultivation and production of secondary metabolites from W. trilobata L. hairy roots.