Spatio-Temporal Variation in the Phyllospheric Microbial Biodiversity of Alternaria Alternata-Infected Tobacco Foliage

Abstract

Phyllospheric microbial composition of tobacco (Nicotiana tabacum L.) is contingent upon certain factors, such as the growth stage of the plant, leaf position, and cultivar and its geographical location, which influence, either directly or indirectly, the growth, overall health, and production of the tobacco plant. To better understand the spatiotemporal variation of the community and the divergence of phyllospheric microflora, procured from healthy and diseased tobacco leaves infected by Alternaria alternata, the current study employed microbe culturing, high-throughput technique, and BIOLOG ECO. Microbe culturing resulted in the isolation of 153 culturable fungal isolates belonging to 33 genera and 99 bacterial isolates belonging to 15 genera. High-throughput sequencing revealed that the phyllosphere of tobacco was dominantly colonized by Ascomycota and Proteobacteria, whereas, the most abundant fungal and bacterial genera were Alternaria and Pseudomonas. The relative abundance of Alternaria increased in the upper and middle healthy groups from the first collection time to the third, whereas, the relative abundance of Pseudomonas, Sphingomonas, and Methylobacterium from the same positions increased during gradual leaf aging. Non-metric multi-dimensional scaling (NMDs) showed clustering of fungal communities in healthy samples, while bacterial communities of all diseased and healthy groups were found scattered. FUNGuild analysis, from the first collection stage to the third one in both groups, indicated an increase in the relative abundance of Pathotroph-Saprotroph, Pathotroph-Saprotroph-Symbiotroph, and Pathotroph-Symbiotroph. Inclusive of all samples, as per the PICRUSt analysis, the predominant pathway was metabolism function accounting for 50.03%. The average values of omnilog units (OUs) showed relatively higher utilization rates of carbon sources by the microbial flora of healthy leaves. According to the analysis of genus abundances, leaf growth and leaf position were the important drivers of change in structuring the microbial communities. The current findings revealed the complex ecological dynamics that occur in the phyllospheric microbial communities over the course of a spatiotemporal varying environment with the development of tobacco brown spots, highlighting the importance of community succession.

Response of microbial communities on tobacco leaf phyllosphere exposed to the broad-spectrum fungicide mancozeb

“…Moreover, the number of fungal OTUs in the healthy groups (treated and untreated) was higher than the diseased groups (Chen et al, 2020;Huang et al, 2021b). These results are in line with previous reports indicating higher OTUs in healthy samples compared to diseased samples (Dai et al, 2022). The diversity and richness of the fungal communities in the healthy groups were higher than the disease-causing G. cichoracearum DC (Huang et al, 2020)d segeticola-infected tobacco leaves (Huang et al, 2021b).…”

“…It could be said that Candida could possibly emerge as a secondary infective agent once the plant becomes susceptible to TBS. The top 10 genera causing tobacco leaf infections include Golovinomyces cichoracearum DC (Huang et al, 2020), Didymella segeticola (Huang et al, 2021b), A. alternata (Dai et al, 2022); the genera that cause asymptomatic and symptomatic infections in tobacco leaves (Xiang et al, 2022) include Alternaria, Cladosporium, Phoma and Boeremia. Generally, these genera are detected during the maturation period of tobacco and form the core fungal microbiome of tobacco phylloplane.…”

Responses of the bacterial community of tobacco phyllosphere to summer climate and wildfire disease

“…Tobacco’s leaves are continually subjected to excessive strong sunlight on summer days, which makes it an ideal material to study the mechanism of bacterial community assembly and succession in the face of strong abiotic stresses (i.e., UV radiation, desiccation and heat), accompanied with pathogen invasion ( Bringel and Couée, 2015 ; Xing et al., 2022 ). Dai et al. (2022) investigated the spatiotemporal variation of the community tobacco leaves affected by brown spot disease and found that the relative abundance of Pseudomonas, Sphingomonas , and Methylobacterium increased as tobacco leaves aging gradually.…”

Phyllosphere bacterial community dynamics in response to bacterial wildfire disease: succession and interaction patterns

“…Comprehensive understanding of these interactions is necessary for predicting disease incidence and severity and finding novel solutions against them. For example, Dai et al. (2022) investigate the spatiotemporal changes in community tobacco leaves infected by brown spot disease.…”