Analysis of the prochloraz-Mn resistance risk and its molecular basis in Mycogone rosea from Agaricus bisporus

BACKGROUND Wet bubble disease (WBD), caused by Mycogone rosea, is one of the most serious diseases of white button mushroom (Agaricus bisporus) in China. Prochloraz-Mn is the main fungicide used in the management of WBD. To provide essential references for early warning of prochloraz-Mn resistance and management of WBD, this study was performed to assess the resistance risk to prochloraz-Mn in M. rosea, as well as its underlying resistance mechanism. RESULTS Eight stable prochloraz-Mn-resistant mutants with a mutation frequency of 1.3 x 10(-4) were generated and resistance factors ranged from 2.57 to 7.80 after 10 successive culture transfers. All eight resistant mutants exhibited fitness penalties in decreased sporulation and pathogenicity. Positive cross-resistance was observed between prochloraz-Mn and prochloraz or imazalil, but not between prochloraz-Mn and diniconazole, fenbuconazole, thiabendazole or picoxystrobin. The point mutation F511I in MrCYP51 protein was found in six mutants and the point mutation G464S occurred only in the SDW2-2-1M mutant. The up-regulated expression of MrCYP51 in all mutants was less than that in their parental isolates when exposed to prochloraz-Mn. Without prochloraz-Mn treatment, MrCYP51 expression was up-regulated in GX203-3-1M and FJ58-2-1M mutants, whereas it was down-regulated in other mutants compared to their respective parental isolates. CONCLUSION Genotypes with two separate point mutations, F511I and G464S in MrCYP51, may be associated with resistance to prochloraz-Mn in M. rosea. The resistance risk of M. rosea to prochloraz-Mn is likely to be low to moderate, indicating that prochloraz-Mn can still be used reasonably to control WBD.

Automated summary

This study found that the resistance risk of M. rosea to prochloraz-Mn is likely to be low to moderate, indicating that prochloraz-Mn can still be used reasonably to control wet bubble disease.