The seed-associated microbiome of four cactus species from Southern Chihuahuan Desert

Abstract

One of the riskiest stages in the reproduction of cactus is the germination of seeds. Although evidence indicates the relevance of the seed-associated microbiome during this stage, little is known about its structure and function. In this work, we explore the diversity of the seed-associated microbiome of cactus, their role in the germination and protection of the emerging embryo. We characterized the microbial communities of the internal tissues (endoseminal) and those that colonize the surface of the seeds (episeminal) of four cactus species (Echinocactus platyacanthus, Ferocactus latispinus, Ferocactus pilosus, and Stenocereus queretaroensis). We sequenced by Illumina the 16S rRNA gene for Bacteria and the ITS1/ITS4 region for fungi. We isolated cultivable microorganisms and characterized their plant growth-promoting abilities. We determined that microbial communities associated with cactus seeds have high richness but are dominated by few taxa, and in most cases, there are clear differences between episeminal and endoseminal microbial groups, especially for fungi. The cactus seed microbiota comprises potential pathogens and beneficial microorganisms that could influence the germination percentage and seedling's development. We can highlight bacterial groups such as Kluyvera, Bacillus, Paenibacillus, and Stenotrophomonas; for fungi, the classes Tremellomycetes, Dothideomycetes, Eurotiomycetes, Leotiomycetes, and Sordariomycetes.