Bioactivity of mefentrifluconazole against different Fusarium spp.

Emergence and development of resistance to 14α-demethylase inhibitors (DMIs) have become a critical issue in both agriculture and medical fields. Mefentrifluconazole, the first isopropanol triazole fungicide belonging to a new subclass of DMIs, has been proposed to show high activity, minimal adverse side effects, and inconsistent cross resistance with other DMIs due to its high structural flexibility. In this study, mefentrifluconazole showed disparate inhibitory activity against the mycelium growth of seven tested Fusarium species. The most sensitive species included F. oxysporum, F. proliferatum, F. commuae, and F. fujikuroi, followed by F. equiseti and F. graminearum, while F. solani was most insensitive. Consistently, mefentrifluconazole presented the strongest inhibiting effects on conidium germination, cell membrane integrity, and ergosterol biosynthesis in F. fujikuroi, followed by F. graminearum, while F. solani ranked last. Further results indicated that all F. fujikuroi isolates causing rice bakanae disease (RBD) were sensitive to mefentrifluconazole regardless of their resistance to prochloraz, tebuconazole, carbendazim, and phenamacril. Additionally, the inoculation tests found that mefentrifluconazole presented a better protective efficacy on rice seedlings when applied 12 h before the F. fujikuroi inoculation, compared to applied 12 h post the inoculation. Overall, this study demonstrated the various bioactivity of mefentrifluconazole combating Fusarium spp. and put new insights into RBD management as well as the applications of DMIs.

Activity of a SDHI fungicide penflufen and the characterization of natural-resistance in Fusarium fujikuroi.

The occurrence of bakanae disease of rice caused by the fungus Fusarium fujikuroi in Zhejiang Province has become increasingly aggravated in recent years, concomitant with the development of resistance to the widely applied fungicides, prochloraz and phenamacril. In this study, the activity of a novel succinate dehydrogenase inhibitor (SDHI) fungicide, penflufen, against different fungi was evaluated in addition to the potential of penflufen in controlling F. fujikuroi infections. Penflufen exhibited good bioactivity against F. fujikuroi, but weak activity against Fusarium spp. and other investigated plant-pathogenic fungi including Colletotrichum spp. In addition to inhibiting mycelial growth, penflufen effectively inhibited F. fujikuroi conidium production. For germination, penflufen could effectively inhibit that of small conidia, but only delay the germination of large conidia. In addition, the sensitivity to penflufen among 100 F. fujikuroi isolates that were collected in areas that were never exposed to SDHIs was determined based on mycelium growth. Sensitivities surprisingly exhibited bimodal distributions, indicating the presence of natural resistance. Cross-resistance was not observed between penflufen in F. fujikuroi and two fungicides that have been extensively applied in field including prochloraz (a DMI) and phenamacril (a 2-cyanoacrylate fungicide), nor with the three SDHIs, fluopyram, benzovindiflupyr, and pydiflumetofen. Additional analysis identified five different point mutations in SDH-A (i.e., at residues 46, 225, 283, 430, and 586) of naturally resistant isolates. These results inform the potential application of the new SDHI fungicide penflufen for managing crop diseases and understanding possible resistance mechanisms among pathogens.

New strategy for detection of hydrogen peroxide based on bi-nucleophilic reaction.

Two novel fluorescent probes based on 7-hydroxy-4-methyl-coumarin, FAA-MC-OH (2-fluoro-4-nitro-phenylacetyl hydroxyl coumarin) and FBA-MC-OH (2-fluoro-4-nitro-benzoyl hydroxyl coumarin) are first synthesized, and spectral studies confirm that both the probes display highly selective and sensitive to H2O2, especially FBA-MC-OH has a shorter response time. Moreover, it is worth noting that the reaction mechanism is based on bi-nucleophilic substitution instead of oxidation or hydrolysis, which is different from previous reported probes'.