| Endophytes are widespread hosted within various plants. Attention was paid to them by researchers in disciplines for their promoting growth, improving resistance of host, being ideal vectors for expressing exogenous genes within plant, and producing active substances against microbes, insects and cancers. Oilseed rape (Brassica napus) is an important oleaginous crop. Kinds of diseases during its growth period are responsible for dramatic yield losses. The objects of this study were to investigate preliminarily the endophytic diversity and fluctuation. We hope to obtain some basic information for further using endophytes and for carrying out the research on endophytes-oilseed rape interactions. In this survey, we isolated endophytic fungi from surface-sterilized healthy oilseed rape and identified them. Forty five endophytic fungi were achieved, including 1 Ascomyteces, 1 Basidiomycetes and 43 Deuteromycetes (40 in Hyphomycetes and 3 in Coelomycetes). Thirty seven belonged to 20 genera, and 8 species were unidentified. There were no apparent dominant species. Alternaria alternate from leaf was the highest frequency, 7.04%. The species amounts of endophytic fungi isolated from different tissues of oilseed rape was variable. We found 25 species from leaf, 12 species from root, 11 species from flower, 12 species from stem and 2 species from seedling. Chaetomium globosum preliminary by re-inoculation was proved a systemic endophytic fungus of oilseed rape. It could be seen from our results that oilseed rape was rich in endophytic fungi. Abundant groups of endophytic bacteria were isolated from surface-sterilized leaves, roots, stems and stalks of oilseed rape. They were categorized to 34 groups based on morphological characters on colony. Dominant groups were obvious different among tissues. Dominant group in root was group B03 (isolative frequency 28.3%), group B01(isolative frequency 20.4%) in leaves. Group B05 (isolative frequency 9.7%) was community from the all tissues. The endophytic bacteria amounts in all tissues were at the high level of 105 cfu/g above. In order to understand the amount fluctuation and interactions between endophytic bacteria within host, endophytic strains bYM3-1 and bYb1-4 with different color were selected. The antibiotics, streptomycin, rifampicin and chloromycetin were used to induce di-anti-antibiobics mutant. Mutant strain SC-bYM3-1 against streptomycin and chloromycetin, and DA-bYb1-4 against streptomycin and rifampicin were obtained. Two kinds of inoculation, seed dipping and root injuring were used respectively with suspensions of strain SC-bYM3-1. We found the amount of endophytic bacteria very high, up to 49.8×103cfu/g at the 1st day after germinating with seed dipping, then decreased to 4.1×103 cfu/g at the 4th day, and an increasing from the 7th to 10th day up to the second peak, thereafter decreased again. It could be isolated at the 22nd day. When treated with root injuring, we found that the amount within oilseed rape increased firstly, and to the first peak at the 7th day with 2.5×103 cfu/g, up to the second peak at the 13 day with 6.6×103 cfu/g before the valley floor at the 10th day, then decreased again. It still could be isolated at the 28th day. The results show that endophytic bacteria could colonize well in oilseed rape and their amounts obviously fluctuate within host. When rape seeds dipped with two strains, SC-bYM3-1 and DA-bYb1-4 at the same time or one by another, we found that fluctuation of the two bacteria were obviously different from that by one strain, and the amount were apparently lower than that of each bacteria. Two endophytic bacteria were competed each other while infecting, and the dominant strain showed high invasive power. |
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