Chiral Fungicide Prothioconazole: Fungicidal Bioactivity And Enantioselectivity In Foc TR4

Banana（Musa spp.）is one of the most important economic crops for many Asian and African countries.Fusarium oxysporum f.sp.cubense（Foc）causes Fusarium wilt（Panama disease）one of the most destructive diseases of banana trees.Foc tropical race 4（TR4）is highly virulent on almost all banana cultivars,whereas efficient strategies for its management are not available to date.The prevention and control of Fusarium wilt of banana is a world challenge and a research hotspot.The selected disease-resistant varieties are playing a key role for the sustainable development of the banana industry,but would be overcome by pathogen evolution,other methods of prevention and control have not achieved major breakthroughs.Chemical fungicides play an important role in the comprehensive control of plant diseases and pests due to their advantages such as high efficiency and convenience,but there are little reports of the chemical control of banana Fusarium wilt so far.Therefore,we futher understanding that chemical fungicides for controlling banana Fusarium wilt is a bottleneck,and we must be overcome the comprehensive banana Fusarium wilt control system.The research group has previously screened a new triazole fungicide prothioconazole,which has a good antibacterial effect against Foc TR4.Meanwhile,the prothioconazole is a chiral fungicide,which consists of a pair of enantiomers（S-prothioconazole and R-prothioconazole）.In this study,enantioselective bioactivity towards Foc tropical race 4,mycotoxin production and enantioselective mechanisms regarding triazole fungicide prothioconazole were investigated.The main results are as follows:（1）R-prothioconazole is higher bioactivity S-prothioconazole on against Foc TR4:the concentrations of S-prothioconazole and R-prothioconazole were between 0.5 and 1μg/m L,the bioactivity increases with the increase of concentration.R-prothioconazole can significantly inhibit the growth rate of hyphae and spore production;Significant difference was found in toxicity of R-prothioconazole and S-prothioconazole to Foc TR4 with EC ₅₀ of0.78μg/m L（R²=0.9703）and 25.31μg/m L（R²=0.9630）,respectively;the enantiomer of R-prothioconazole powerfully induced H₂O₂ formation,yet drastically reduced superoxide disproportionation antioxidant enzyme activities of and catalase（CAT）and superoxide dismutase（SOD）,which led to an oxidative stress;R-Prothioconazole induced significantly increased accumulation of membrane lipid peroxidation product MDA and enzyme P450cytochrome activity（CYP450）;R-prothioconazole displayed elevated sensitivity to sodium dodecyl sulfate（SDS）and Congo red（CR）,which are common cell wall-damaging agents;the enantiomer of S-prothioconazole mycelium is slender and has many branches compared to R-prothioconazole and control.（2）R-prothioconazole showed stronger inhibition for Fusaric acid（FSA）and Beauverin（BEA）production than S-prothioconazole,the concentrations of S-prothioconazole and R-prothioconazole were between 0.5 and 1μg/m L,due to the concentration increases,the content of fusaric acid（FSA）and beauverin（BEA）decreases.Meanwhile,R-Prothioconazole induced significantly decreased expression of the FSA biosynthetic genes clusters（FUB1,FUB2,FUB3,FUB4,FUB5）and BEA（BEAS）compared to S-prothioconazole,the effects on genes expression and mycotoxin production showed positive correlation.（3）The interaction between the prothioconazole enantiomer and the Foc TR4:R-Prothioconazole induced significantly increased cytochrome P450 activity（CYP450）;R-prothioconazole showed greater expression for target genes Foc CYP51-2,Foc CYP51-3and target protein Foc Cyp51A than S-prothioconazole;Homology modeling and molecular docking predicted that R-prothioconazole and CYP51 had stronger binding affinity than S-prothioconazole,Thr127 and Phe131 interacted with the benzene ring and cyclopropane of R-prothioconazole,and Tyr123 interacted with The benzene ring of S-prothioconazole interacts.