Basic Composition and Structure of the Phyllosphere Fungal
Community of Rubber Trees with Powdery Mildew
A total of 593,237 high-quality sequence fragments were obtained from
the 16 samples of rubber tree powdery mildew fungi via MiSeq
high-throughput sequencing. The number of sequences in a single sample
ranged from 30,129 to 44,619, with an average of 37,077, and a total of
1406 OTUs were detected. Their average sequence length was 293.01 bp,
with 57.38% of the sequences being 301–320 bp in size and 26.99%
being 241–260 bp. The samples’ dilution curves showed differences in
their fungal diversity. The general flattening of these dilution curves
indicated that the amount of sequenced data was robust, and that the
depth of sequencing largely covered all species in the rubber tree leaf
samples (Figure S1).
A total of 1398 OTUs were detected in the four regions after quality
control, with a ranking of WZS > WN > BS
> DZ (Figure 1). There were 90 overlapping OTUs across the
four regions, accounting for 6.44% of the total number of OTUs in all
pooled samples. This indicated that although the samples were all
sourced from the rubber powdery mildew phyllosphere, there were stark
differences in OTU levels among the four rubber tree-growing regions.
The community composition of each sample was calculated at different
taxonomic levels, for which a total of six phyla, 26 classes, 69 orders,
157 families, and 351 genera of fungi were identified. At the phylum
level, the community composition of samples from all four regions was
similar, with Ascomycota and Basidiomycota dominating,
though their relative abundances varied across regions (Figure 2-1). The
relative abundance of Ascomycota ranged from 43.76% to 99.80%,
and that of Basidiomycota ranged from 0.17% to 10.91% in the 16
samples (Figure 2-2).
The dominant genera in all four regions consisted of Erysiphe andCladosporium . In addition, the dominant fungal taxa of the
regions’ healthy leaves differed (Figure 2-2). The dominant genera in
the Level 3 leaves of the samples from the four regions are listed in
Table S4. In addition, the healthy leaves (Level 0) and Level 3 leaves
in the four regions also included a number of less abundant community
members. The relative abundance of fungi (others) whose taxonomic status
was unclear or not yet identified ranged from 1.04% to 10.58% (Table
S4).
In summary, apart from WZS, the dominant fungal genera in the other
three regions for both Level 3-infected leaves and healthy leaves
consisted of Erysiphe and Cladosporium , with one to three
different subdominant genera per region, albeit all at low relative
abundances. Therefore, the two levels of infected and healthy leaves of
rubber trees growing at the same site differed in the relative abundance
of phyllosphere microbiome but not in the genus-level community
composition, whereas the latter varied across the four regions. Although
powdery mildew had little effect on the structure of the phyllosphere
fungal community, it did affect the relative abundance of each
community.