Effect of Fungicides on Bayberry Decline Disease by Modulating Rhizosphere Soil Properties, Microflora, and Metabolites

Abstract

Decline disease causes serious damage to bayberry, but the reasons behind this disease are not completely understood, although fungal pathogenicity factors have been proposed. Our past studies have identified that the adversity of this disease is linked to the application of soil fungicide. The objective of this study is to explore the mechanism and alleviation effect of the use of the fungicide prochloraz in this disease by investigating the plant and soil parameters. The results of the current study reveal that the application of prochloraz could improve the tree vigor and fruit quality of decline-diseased bayberry. The beneficial effect of prochloraz on plant growth and fruit quality may be associated with its influence on the rhizosphere soil properties and soil microbiota. Indeed, the application of prochloraz was shown to significantly affect the relative abundance and diversity of the rhizosphere soil microbiota, with it having a greater effect on bacteria than on fungi. Furthermore, the community composition of rhizosphere soil bacteria and fungi at the genus level was found to be significantly affected by the pH, available phosphorus, alkali-hydrolyzable nitrogen, and exchangeable magnesium, which exhibited a greater effect on bacteria than on fungi. In addition, prochloraz significantly affected the metabolic pathways of pyrimidine, galactose, butanoate, arginine, and proline and changed the contents of 58 metabolites, with an 18.59–149.48% increase seen in 51 metabolites and a 31.52–95.21% reduction seen in 7 metabolites. Interestingly, these metabolites were found to be significantly correlated with the rhizosphere soil microbiota at the levels of phylum, order, and genus. Overall, the results of this study provide an alternative choice for protecting bayberry from the damage caused by decline disease.