Impact of carbon-starved Pseudomonas aeruginosa strain IE-6S+ on the diversity of culturable fungi in the rhizosphere and within roots of mungbean.

摘要

Mung bean (Vigna radiata) was grown repeatedly in sandy loam soil which was either left untreated (control) or was treated with Pseudomonas aeruginosa strain IE-6S+ or its carbon-starved derivatives. Bacterial inoculants were applied to the soil at the start of each 52-day-long mung bean growth cycle and their effect on the diversity of the rhizosphere populations of cultureable fungi was assessed at the end of the first and fourth cycles. A total of 23 fungal species belonging to 18 genera were isolated from the rhizosphere of mung bean. There was a marked difference among the growth cycles with respect to fungal community composition; only slight differences occurred across the bacterial treatments. At fourth growth cycle, general diversity and equitability were lower in soils treated with wild type IE-6S+ while higher in those treated with IE-6S+ PBK1 or IE-6S+ KUC2. Following IE-6S+ KUC2 treatment, fungal abundance pattern was described by geometric series while those following treatment with IE-6S+ or IE-6S+ PBK1 were found to conform to MacArthur's broken-stick model at first growth cycle. Nine fungal species comprising 7 genera were found to colonize mung bean root tissues. Roots grown in untreated soils gave high colony forming units of the parasitic fungi while those treated with bacterial treatments harboured mostly saprotrophic fungi. When compared to the controls, general diversity, equitability and species richness of the culturable endophytic fungi were slightly higher in mung bean roots treated with the bacterial inoculants. Abundance patterns of root-fungi in the controls and following bacterial treatments could be described by both geometric and broken-stick models..