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.

Effect of Humic Acid on Soil Physical and Chemical Properties, Microbial Community Structure, and Metabolites of Decline Diseased Bayberry

“…In agreement with the result of this study, our previous studies have shown that HA had the same effect on bayberry as fertilizer and fungicide on the growth of the plant and the quality of the fruit [ 3 , 22 ]. Furthermore, these data are also comparable to the findings of Nardi et al [ 11 ], who found that humic acid can directly impact the photosynthesis of plants.…”

“…The result of this study suggests that humic acid had a greater effect on the bacterial richness of rhizosphere soil of declining diseased trees than on fungi. In agreement with the result of this study, our previous studies have shown that HA had the same effect on the variety and richness of the rhizosphere soil of decline diseased bayberry as a compound fertilizer and fungicide [ 22 , 24 ].…”

“…In addition, six replicates of the humic acid treatments revealed a better bacterial diversity compared to the diseased control than those of the fungal community structure ( Figure 2 ). In accordance with the findings of this study, the structure and percentage contribution of soil microorganisms differed between fertilizer or fungicide-treated and untreated soil [ 22 , 24 ].…”

“…The result of this study revealed the complexity of the relationship between microbial growth and soil nutrient elements. Furthermore, the result obtained demonstrated that the order of contribution rates of soil physical and chemical indexes and nutrient elements to bacteria and fungi is different from that of untreated healthy trees, diseased trees, fertilizer-treated diseased trees and fungicide-treated diseased trees [ 3 , 22 , 24 ]. This data suggests that a balance of nutrients may be the best for microbial growth.…”

“…Through the metabolism of arginine and proline, the resistance to cold stresses will be improved, which was able to promote the recovery and healthy growth of the root system of bayberry. The significant change in galactose metabolism after humic acid treatment is the same as those of diseased trees treated with fungicides and fertilizers, but the number of pathways was greater than that of fungicides and fertilizers [ 22 , 24 ].…”