Bacterial community structure associated with healthy and cladode-thickened of Opuntia ficus-indica plants during the dry and rainy seasons

Abstract

Opuntia ficus-indica is renowned for its resilience to adverse environmental conditions. However, it remains susceptible to various diseases caused by both biotic and abiotic factors. Among these diseases, cladode thickening represents a significant agronomic limitation. Although phytoplasmas and viruses have been suggested as potential causal agents, its etiology remains unknown. This study aimed to characterize the structure, diversity, and phylogenetic relationships of bacterial communities across different compartments of cultivated O. ficus-indica, comparing healthy and thickened plants during the rainy and dry seasons through 16S rRNA gene amplicon sequencing, to assess the potential role of bacteria in the etiology of this disease. Five ecological compartments were analyzed: soil, rhizosphere, root tissue, phyllosphere, and cladode tissue. The V3-V4 region of the 16S rRNA gene was sequenced from bacterial communities, and bioinformatic analyses were conducted using the Mothur pipeline. Soil and root compartments exhibited the highest alpha diversity. This is due to their role as reservoirs of stable and functionally diverse microbial communities. Aerial compartments, on the other hand, showed lower diversity. The structure of bacterial communities in the phyllosphere, cladode tissue, and rhizosphere varied mainly according to the health status of the plant, while soil and root communities were influenced by environmental conditions. In thickened plants, the bacterial composition was similar across compartments, while in healthy plants, the communities were more distinct and compartment specific. Seasonal dynamics shaped the distribution of bacterial taxa across compartments: fewer taxa were shared during the rainy season, while a greater number of taxa were shared across multiple compartments under dry conditions, suggesting a potential role in adaptation to water-limited environments. Despite these compositional differences, no specific taxon could be directly linked to the etiology of the thickening disorder.