**5. Conclusions**

The risk of resistance selection in *B. cinerea* due to the extensive application of DCs (iprodione) may be a severe problem in Guangxi Province China. In the current study, the results showed that *B. cinerea* isolates were sensitive to iprodione The laboratory UV induced resistant mutants were obtained through continuous iprodione treatment, which indicated that *B. cinerea* quickly adopt resistance to iprodione. The resistant mutant demonstrated an EC50 value 1025.74 μg/mL higher than curative dosage. The resistant mutant had a high level of fitness (mycelial growth, sclerotia formation and aggressiveness) as compared to sensitive isolates. We identified two mutation points at codon 593 (A198E) and 599 (F200Y) in the *bctubA* gene, including one novel point mutation in *bctubB* gene at position 646 codon. Our research work also provided a comprehensive molecular mechanism involved

in the *B. cinerea* resistant mutant. By analyzing RNA sequencing data for wild type and mutant with or without iprodione application, genes related to iprodione resistance were highlighted and identified. These DEGs were involved in the production of detoxification enzymes, metabolism, catalytic activity, MAPK signaling pathway, drug e fflux, and transporter functions to resist the chemicals. Resistant managemen<sup>t</sup> strategies should be implemented to delay the spread of iprodione resistant mutants in the field. Furthermore, integrated disease managemen<sup>t</sup> strategies should be practiced followed, including the use of biological control and agricultural practices.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/1422-0067/21/14/4865/s1.

**Author Contributions:** Conceptualization, A.M., C.W., and H.W.; methodology, A.M.; software, A.M.; validation, S.A., C.W., and A.M.; formal analysis, A.M., C.W., and S.A.; investigation, A.M. and H.W.; resources, H.W.; data curation, A.M. and S.A.; writing—original draft preparation, A.M.; writing—review and editing, A.M., C.W., S.A., and H.W.; supervision, H.W. All authors have read and agreed to the published version of the manuscript.

**Funding:** We express our sincere gratitude to Guangxi Innovation Team of National Modern Agricultural Technology System (nycytxgxcxtd-10-04), the National Natural Science Foundation of China (31660511), Construction project of characteristic specialty and experimental training teaching base (Center)—Characteristic specialty—Plant Protection (2018–2020).

**Conflicts of Interest:** The authors declare that the research was conducted in the absence of any commercial or financial relationship that could be construed as a potential conflict of interest.
