Association between rhizosphere microbiome and hybrid weakness of the endangered mangrove hybrid plant Sonneratia×hainanensis

Abstract:

[Objective] To study the morphological and physiological characteristics of hybrids compared with their parents and contribute to research on the mechanisms of speciation and evolution. [Methods] Sonneratia×hainanensis, a natural hybrid of the mangrove plants Sonneratia alba and S. ovata, usually presents hybrid weakness than its parents. In this study, Illumina high-throughput sequencing was employed to compare the rhizosphere microbiomes (including bacteria and fungi) between the hybrid and its parents, on the basis of which the reason for hybrid weakness was explored. [Results] The principal coordinate analysis (PCoA) revealed no significant difference in the rhizosphere bacterial or fungal community structure between the hybrid and its parents. However, the rhizosphere microbiome of the hybrid was different from that of the female parent S. alba with strong survival ability but similar to that of the male parent S. ovata. The rhizosphere bacteria belonged to 388 genera, 320 families of 76 phyla. The dominant phylum Pseudomonadota had the relative abundance above 41.00% in the rhizosphere of the three plant species, reaching 55.33% in the hybrid, which was higher than that in the parents. At the genus level, 18 common genera including Desulfococcus (3.23%) and Rhodoplanes (0.94%) in all the three mangrove plants showed the relative abundance of 15.77%. Among them, 8 salt-tolerant genera such as Mariprofundus showed decreased relative abundance in the hybrid, which may affect the salt tolerance. The rhizosphere fungi were dominated by Ascomycota and Basidiomycota with the relative abundance of 41.89% and 4.53%, respectively, which was significantly lower than that in the parents. Moreover, the predominant fungal genera were different in the three mangrove plants. Functional annotation of prokaryotic taxa (FAPROTAX) predicted that the mangrove prokaryotes were involved in sulfur metabolism and nitrogen metabolism. Although the hybrid had higher Shannon and Simpson indexes of rhizosphere bacteria than S. alba, some dominant taxa such as B-42 (unclassified Trueperaceae), Mariprofundus, and Sulfurimonas participating in the nitrogen cycle were not inherited by the hybrid. The soil total nitrogen (TN) and total phosphorus (TP) of the hybrid was significantly lower than that of S. alba. TN was significantly positively correlated with the relative abundance of Mariprofundus, B-42, Aspergillus, and Rhodotorula, which, however, demonstrated decreased relative abundance in the rhizosphere of the hybrid. [Conclusion] The results help to understand the mechanisms of hybrid weakness in Sonneratia×hainanensis.