Abstract:
Tobacco target spot is a fungal disease on tobacco. In this paper, the mycelial growth rate method was used for the potential evaluation of dimetachlone to
Rhizoctonia solani, and the effect of dimetachlone on the microbes of tobacco leaves after different periods of application was studied with Illumina high-throughput sequencing technology as well. Results showed that dimetachlone had strong inhibitory activity against the mycelial growth of
R. solani with an EC
50 value of 1.20 μg/mL and a complete inhibition of mycelial growth at 6.47 μg/mL. Within 0-18 days of treatment with 4200 g/hm
2 dimetachlone 40% WP, there were significant differences in microbial community structure between healthy and diseased tobacco leaves. The phyllosphere fungi in both healthy and diseased tobacco were all distributed in
Thanatephorus,
Alternaria, and
Fusarium, the phyllosphere bacteria in tobacco leaves were
Pseudomonas,
Staphylococcus, and
Sphingomonas. Three days after application, the relative abundance of
Thanatephorus in healthy and diseased tobacco leaves decreased 12.41% and 51.62%, the relative abundance of
Alternaria increased 0.54% and 0.42%, the relative abundance of
Pseudomonas decreased 13.48% and 19.17%, respectively. Nine days after application, the relative abundance of
Thanatephorus in healthy and diseased tobacco leaves decreased 1.38% and 47.42%, the relative abundance of
Alternaria decreased 0.36% and 0.18%, the relative abundance of
Pseudomonas decreased 2.73% and 2.73%, respectively. Eighteen days after application, the relative abundance of
Thanatephorus in healthy and diseased tobacco leaves decreased 26.74% and 39.03%, the relative abundance of
Alternaria increased 26.02% and 2.70%, the relative abundance of
Pseudomonas increased 6.56% and 16.02%, respectively. The application of dimetachlone 40% WP in the field significantly suppressed the relative abundance of
Thanatephorus genus in healthy and diseased tissues within 3 d, but the effect on disease tissues was greater than that on healthy leaves; it also caused changes in the structure of interleaf bacterial flora, but the effect on diseased leaves was less than that on healthy tobacco leaves. The results of the study revealed the differences in the phyllosphere microorganism communities between healthy and diseased interleaf tissues after the application of dimetachlone from a microscopic perspective, providing a scientific basis for the application of dimetachlone.