Studies On The Foliar Microflora Of Bamboo Forests In Sichuan

Cultivated bamboo forest, distributed mainly in southwest Sichuan Province, consists of a wide range of species with various usages. In early 2008, an unusual rainfall and a snowstorm destroyed a large population of the bamboo forest, and caused a significant loss in bamboo production in different areas. These adverse weather conditions affected health of the bamboo plants, including bamboo leaves. Not only reflect the growing condition of the entire bamboo plant, bamboo leaves are also important organs which provide an ideal habitat for many microorganisms and an entry for pathogen to colonize the entire system. These microorganisms, both on the surface and inside of the leaves, are abundant, belong to various species, and can form complex yet steady micro-ecosystem.Six species of bamboo plants cultivated in Ya'an (B. pervariabilis×D. grandis, N. affinis), Yibin (P. heterocycla, B. rigida) and Luzhou (D. farinosus, B. multiplex) were studied in this research. After the recovery from the snowstorm, traditional forest pathology and molecular biology methods were used to investigate seasonal dynamics of cultivable microorganisms'quantity and compositions of foliar sample from the bamboo plants. The following results have been obtained:①The foliar microflora of bamboo plants mainly consisted of fungi and bacteria, with bacteria as the dominating microorganism.The total microorganism counts were significantly correlated (P<0.05) or highly significantly correlated (.P<0.01) with bacteria counts. The counts of phylloplane fungi, actinomycetes and microorganism of N. affinis leaves were significantly correlated (P<0.05) with each other; the endophyte counts of B. rigida leaves had significant correlation (P<0.05) with bacteria's and total microorganism's counts as well. Seasonal dynamics of microorganism's total counts were similar to the bacteria counts, but different from fungi and actinomycetes of the same bamboo species. Seasonal dynamics of total microorganism counts were different among different species in different locations, and species in the same locations except the two species in Luzhou area (D. farinosus, and B. multiplex). In this study, bamboo species and seasonal changes were the two major factors that influenced the total microorganism counts. Results of double-factor ANOVA also showed that the two factors had different influences on different microorganism populations.②The microorganisms isolated from the six species at the three locations demonstrated various differences in population composition, dominant population, and their responses to seasonal changes.In Ya'an area, samples isolated contained 43 genera and 60 species of fungi,14 genera and 24 species of bacteria, and 1 genus and 1 species of actinomycetes. The microorganism population was significantly larger than the microorganisms isolated from samples collected from the other two locations. Samples from Yibin contained 26 genera and 33 species of fungi,12 genera and 17 species of bacteria, and sample collected from Luzhou contained 23 genera and 32 species of fungi, and 11 genera and 17 species of bacteria. Similar trend was found with the commonly seen microorganism counts from different locations as well. In Ya'an, the phylloplane and endophytic microflora of two bamboo forests had common species. Similarly, it was also in samples collected in Yibin except the endophytic bacteria. However, samples collected in Luzhou only had common species in phylloplane and endophytic fungi, the bacteria populations were remarkably difference on compositions between phylloplane microflora and endophytic microflora.③The variations of species richness indexes between different bamboo forests in the same area were inconsistent.In samples collected from Ya'an, responses to seasonal changes of different microorganism populations varied. For example, phylloplane population of N. affinis leaves showed the opposite tendency, but similar tendency among endophytic populations in B. pervariabilis×D. grandis leaves. Species richness indexes of same microorganism population between different bamboo species did not show a clear trend, except phylloplane fungi of N. affinis leaves were more abundant than that of B. pervariabilis×D. grandis leaves in four seasons.In Yibin, similar seasonal responses were found among different microorganism populations of P. heterocycla leaves, but not that of B. rigida leaves. Between the two different bamboo species, the species richness indexes of phylloplane fungi of B. rigida leaves were larger than that of P. heterocycla leaves in four seasons, but the endophytic bacteria index were lower in B. rigida than that of P. heterocycla leaves in four seasons except for winter.In Luzhou, results showed different variation tendency between different bamboo species and microorganism populations.④During the survey, commonly seen pests were also discovered at different seasons and among different bamboo species. The main fungal disease was sooty blotch, which was directly related to the widespread phylloplane sooty moulds (C. cladosporioides, Alternaria alternate, et al.). The main insect was defoliator (Algedonia coclesalis, et al.) and aphids (Aphidoidea). There were also some potential pathogens in the foliar microflora and dominant species, and some beneficial microorganisms.