Location: Subtropical Plant Pathology ResearchTitle: Study on plant endophyte PLFAs polymorphism in different spatial of citrus HLB (huanglongbing)) Author
Submitted to: Chinese Journal of Eco-Agriculture
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/8/2012
Publication Date: 7/15/2012
Citation: Zheng, X., Liu, B., Sun, D., Zhu, T., Duan, Y., Xia, Y., Ruan, C., Xiao, R. 2012. on plant endophyte PLFAs polymorphism in different spatial of citrus HLB. Chinese Journal of Eco-Agriculture. 20(7):1-13. Interpretive Summary: Huanglongbing (HLB) is the most destructive citrus disease worldwide and the natural, non-disease forming microbial communities of citrus may be associated with the disease. In this research the endophytic community in red pomelo was analyzed using phospholipid fatty acid (PLFA) profiles to study the microbial community structure. A total of 42 PFLAs were detected in red pomelo. Nine were distributed throughout the plant samples and 33 were mainly distributed in different leaf orientations. Spatially the PLFA’s clustered in two groups where group I had an incomplete distribution, but group II appeared in almost all samples. Differences in the PLFA content and composition existed in leaves of differing health conditions and spatial orientations. The maximum PLFA content was in east-oriented leaves and healthy leaves contain more PLFAs than HLB-affected leaves. In addition, south-oriented leaves had the highest fungi/bacteria PLFAs ratio and also a higher Gram+/Gram- PLFA ratio than north/west-oriented leaves. There was no significant difference in fungi-to-bacteria PLFAs ratio at different leaf levels. However, significant differences existed in PLFAs Gram+/Gram- ratio with the highest ratio being in the upper leaves and the lowest ratio being in the middle leaves of the plant. The fungi-to-bacteria PLFA ratio was higher in healthy leaves than in HLB-affected leaves. Diversity indexes indicated significant differences among the endophytic communities of leaves with different spatial orientations and different health status. The two major principle components accounted for 83% of this variation. HLB-affected leaves were clustered in a separate group from the healthy leaves. The results indicate that the distribution of PLFAs was related more closely with the leaves health condition than their orientation.
Technical Abstract: Huanglongbing (HLB, a yellow shoot disease) is the most destructive citrus disease in the world. Plant endophytic communities of red pomelo have been associated with HLB. It was therefore important to investigate the endophytic community of red pomelo plant in relation to HLB. In this paper, endophytic community structures in different spatial positions and healthy conditions of HLB-affected red pomelo plants were analyzed using phospholipid fatty acids [PLFAs biomarkers based at Sherlock MIS (MIDI Inc.)]. Based on the results, 42 PLFAs were detected and 9 of them had wild distributions across all the samples while the other 33 were mainly distributed in different leaf orientations. Cluster analysis showed that PLFAs in different leaves in space existed into two community groups. While PLFAs in the group I belonged to an incomplete distribution, PLFAs in group ' were distributed almost in all samples. There existed some differences in PLFAs content and composition in leaves of HLB-affected red pomelo plants in different spatial positions and health conditions. When compared among each other, it was noted that PLFAs content in east-oriented leaves were maximum among different orientations. The same was true for lower parts leaf in PLFAs content. Healthy leaves contain more PLFAs than HLB-affected leaves. Furthermore, south-oriented leaves had the highest fungi/bacteria PLFAs ratio and also higher G+/G- (gram-positive bacteria/gram-negative bacteria) PLFAs ratio than north/west-oriented leaves. There was no significant difference in fungi-to-bacteria PLFAs ratio at different leaf levels. However, significant differences existed in PLFAs G+/G- ratio in different height leaves. While the highest ratio occurred in the leaves at the upper parts of plant, the lowest ratio was in leaves at the middle parts of plant. Fungi-to-bacteria PLFAs ratio was higher in healthy leaves than that in HLB-affected leaves. Diversity indexes of Shannon, Simpson and Pielou, endophytic communities among leaves with different orientations and healthy conditions were significantly different. However, no apparent differences were noted among different heights leaves. Principal component analysis showed that the first and second principal components accounted for a total of 82.99% of the variation, which may distinguish endophytic communities in leaves with different orientations. Cluster analysis divided healthy leaves in two groups, and HLB-affected leaves in the other group. The results indicated that the distribution of PLFAs was related with health conditions and orientations of leaves, and was more closely in the former than the latter.