Polyploidy and plant-fungus symbiosis: evidence of cytotype-specific microbiomes in the halophyte Salicornia (Amaranthaceae)

Abstract

Polyploidy is recognized as a mechanism of speciation in plants with cascading effects on biotic interactions. However, a limited number of studies have investigated the effects of polyploidy on the association of plants and microorganisms. Herein, we investigated whether two Salicornia cytotypes (S. europaea - 2x and S. procumbens - 4x) show different root-associated fungal communities. Additionally, we explored the existence of cytotype-specific root anatomical traits, which could influence fungal recruitment and establishment. Salicornia spp. were identified based on their ploidy level. The root-associated fungal microbiome of Salicornia was analyzed using high throughput amplicon sequencing (ITS1 of rDNA) in spring and summer. The following root anatomical traits were investigated: maximum root diameter, periderma thickness, parenchyma thickness, diameter of the vascular cylinder and maximum diameter of parenchyma cells. Our results showed that Shannon diversity and evenness indices were higher in samples of Salicornia procumbens (4x) compared to those of S. europaea (2x), and in summer the root-associated fungal community of S. procumbens (4x) was significantly different from that of S. europaea (2x). The orders Xylariales, Malasseziales and Pleosporales were the most frequent root colonizers in both cytotypes and most of the taxa associated with Salicornia were functionally classified as saprophytes or plant pathogens. Finally, we observed larger periderma and parenchyma layers in S. procumbens (4x) than S. europaea (2x) that may contribute to the observed differences in community composition between the two cytotypes. Our results suggest that differences in ploidy may modulate plant interaction with fungi by affecting species recruitment and microbiome structure. In addition, cytotype-specific root traits may also have the potential to affect differently community assembly in the two cytotypes.