Abstract
BackgroundTheobroma cacao L. (cacao) is a perennial tropical tree, endemic to rainforests of the Amazon Basin. Large populations of bacteria live on leaf surfaces and these phylloplane microorganisms can have important effects on plant health. In recent years, the advent of high-throughput sequencing techniques has greatly facilitated studies of the phylloplane microbiome. In this study, we characterized the bacterial microbiome of the phylloplane of the catongo genotype (susceptible to witch’s broom) and CCN51 (resistant). Bacterial microbiome was determined by sequencing the V3-V4 region of the bacterial 16S rRNA gene.ResultsAfter the pre-processing, a total of 1.7 million reads were considered. In total, 106 genera of bacteria were characterized. Proteobacteria was the predominant phylum in both genotypes. The exclusive genera of Catongo showed activity in the protection against UV radiation and in the transport of substrates. CCN51 presented genus that act in the biological control and inhibition in several taxonomic groups. Genotype CCN51 presented greater diversity of microorganisms in comparison to the Catongo genotype and the total community was different between both. Scanning electron microscopy analysis of leaves revealed that on the phylloplane, many bacterial occur in large aggregates in several regions of the surface and isolated nearby to the stomata.ConclusionsWe describe for the first time the phylloplane bacterial communities of T. cacao. The Genotype CCN51, resistant to the witch’s broom, has a greater diversity of bacterial microbioma in comparison to Catongo and a greater amount of exclusive microorganisms in the phylloplane with antagonistic action against phytopathogens.
Highlights
Theobroma cacao L. is a perennial tropical tree, endemic to rainforests of the Amazon Basin
We show that the differences in the index of glandular trichomes in the contrasting genotypes may affect the variety of bacterial microbioma symbiont of the phylloplane, and that the CCN51 genotype presents an exclusive genera with antagonistic potential against phytopathogens in relation to the catongo genotype, reinforcing its preference of agriculture for the cultivation and commercialization
After pre-processing, filtering and rarefaction, the sequencing produced a total of 1.7 million reads of the V3-V4 variable region of the 16S rRNA from leaf water washes of the two contrasting cacao genotypes for resistance of witches’ broom disease, caused by M. perniciosa fungus
Summary
Theobroma cacao L. (cacao) is a perennial tropical tree, endemic to rainforests of the Amazon Basin. The microorganisms that live in this region multiply and occupy newly formed niches while the leaves are expanding [2, 3] They are influenced by sunlight and the plants metabolism that have nutrients, The phylloplane microorganisms can be shared randomly among its neighbors, but their survival and presence is generally regulated by the plant [10]. Santana et al BMC Microbiology (2018) 18:194 proposes a possible transfer of microorganisms through generations [11] This whole microbiome can be affected by environmental factors, including radiation [12] and pollution [13], as well as biotic factors such as leaf age and the presence of other microorganisms [14]. This variation is observed in different species of plants that have characteristic communities of bacteria in the phylloplane, varying between genotypes [23, 24], as well as between species and taxonomic classifications [17]
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