Pseudomonas chlororaphis metabolites reduce MfCYP51 expression and yield synergistic efficacy in mixture with reduced rates of propiconazole against DMI-resistant Monilinia fructicola isolates.

Brown rot caused by Monilinia fructicola is one of the most important diseases affecting peach production in the southeastern USA. Management often involves the use of demethylation inhibitor (DMI) fungicides, but efficacy can be compromised due to overexpression of the MfCYP51 gene encoding the 14α-demethylase of the ergosterol biosynthesis pathway. This study aimed to investigate the influence of the biorational fungicide Howler EVO containing Pseudomonas chlororaphis ASF009 metabolites, on the expression of MfCYP51 in M. fructicola and associated synergy with a DMI fungicide for control of DMI-resistant strains. Mycelia from two DMI-sensitive and three DMI-resistant M. fructicola isolates were exposed or not to propiconazole (0.3 µg/ml), Howler (78.5 µg/ml), or the combination propiconazole + Howler for 6 h prior to RNA extraction. Real-time PCR indicated that Howler reduced the constitutive expression of MfCYP51 in DMI sensitive and two of three DMI-resistant isolates. Propiconazole-induced expression of the DMI target gene was significantly reduced by Howler and by the mixture of Howler plus propiconazole in all isolates. Detached fruit studies on apple revealed that the combination of Howler plus a reduced label rate of Mentor (50 µg/ml propiconazole) was synergistic against brown rot caused by a DMI-resistant isolate in high and low inoculum spore concentration experiments (synergy values of 40.1 and 4.9, respectively). We hypothesize that the synergistic effects against M. fructicola resistant to DMI fungicides based on MfCYP51 gene overexpression can be attributed to reduced 14α demethylase production due to transcription inhibition, which may necessitate fewer DMI fungicide molecules to arrest fungal growth. The use of Howler /DMI mixtures for brown rot control warrants further investigation because such mixtures could potentially allow for reduced DMI fungicide use rates in the field without compromising yield or increased resistance selection.

Bioproducts of Pseudomonas chlororaphis suppress DMI fungicide-induced CsCYP51A and CsCYP51B gene expression in Colletotrichum siamense and generate synergistic effects with metconazole and propiconazole.

Mixtures of fungicides with different modes of action are commonly used as disease and resistance management tools, but little is known of mixtures of natural and synthetic products. In this study, mixtures of metabolites from the rhizobacterium Pseudomonas chlororaphis strain ASF009 formulated as Howler EVO with below label rates (50 µg/ml) of conventional sterol demethylation inhibitor (DMI) fungicides were investigated for control of anthracnose of cherry (Prunus avium) caused by Colletotrichum siamense. Howler mixed with metconazole or propiconazole synergistically reduced disease severity through lesion growth. Realtime PCR showed that difenoconazole, flutriafol, metconazole, and propiconazole induced the expression of DMI target genes CsCYP51A and CsCYP51B in C. siamense. The addition of Howler completely suppressed the DMI fungicide-induced expression of both CYP51 genes. We hypothesize that the downregulation of DMI fungicide-induced expression of the DMI target genes may, at least in part, explain the synergism observed in detached fruit assays.

Influence of Propiconazole and Metconazole Formulations on Bacillus subtilis Vegetative Cell Growth and Disease Control of Fruit Crops.

Biological control agent Bacillus subtilis formulated as Theia is registered for control of fungal and bacterial diseases of fruit crops. Combinations of Theia and strategic concentrations of two demethylation inhibitor (DMI) fungicides were investigated to explore potential synergisms. Bacteria were cultured in nutrient broth and combined with technical grades and two formulations of propiconazole (emulsifiable concentrate [EC] and wettable powder) and metconazole (EC and water-dispersible granule) at 0, 10, 50, 100, and 150 µg/ml of active ingredient. After cocultivation, the optical density (OD600) and colony forming units (CFU/ml) were evaluated. In contrast to EC formulations, the wettable powder or water-dispersible granule formulations at 10 or 50 µg/ml of both DMIs did not affect vegetative cell growth. The mixture of Theia and each formulated DMI at 50 µg/ml of active ingredient resulted in a significant reduction of Monilinia fructicola lesion development on apple, Colletotrichum siamense lesion development on cherry, and Botrytis cinerea lesion development on cherry. The combination of Theia with EC formulations showed weaker disease reduction due to antagonism. Only Theia plus non-EC formulated propiconazole and metconazole significantly reduced brown rot disease incidence of apple compared with the respective solo treatments and anthracnose disease incidence of cherry compared with the untreated control. Our results indicated that at least some DMI fungicides possess bactericidal effects depending on the formulation and concentration. The combination of Theia with a lower-than-label-rate concentration (50 µg/ml) of the DMI fungicides propiconazole and metconazole showed potential for synergistic effects, especially when non-EC formulations were used.

The effect of deloading tape on medial gastrocnemius muscle fascicle behaviour during dynamic exercise.

This study examined the effect of diamond deloading tape on medial gastrocnemius (MG) muscle behaviour during exercise in healthy adults (n = 27). A randomised cross-over trial assessed the effect of tape (no-tape, sham-tape and deload-tape) on ankle and MG fascicle kinematics during three heel raise-lower exercises [double leg (DL), single leg (SL) and loaded single leg (LSL)]. There was no effect of tape on standing fascicle length (FL) or pennation angle (PA), or ankle or knee joint angle. There was a significant effect of tape on ankle kinematics for all exercises. Both the deload-tape and sham-tape resulted in less ankle plantar flexion but had no effect on dorsiflexion. There was a significant effect of tape on FL change for the SL and LSL exercise. Compared to no-tape, the deload-tape resulted in less fascicle shortening during ankle plantar flexion, and more fascicle lengthening during ankle dorsiflexion. For the LSL exercise, deload-tape caused MG fascicles to operate at longer lengths, for a given joint angle. Diamond taping, with or without added tension, has only a small effect on ankle and MG fascicle kinematics during the heel raise-lower exercise. With the exception of the LSL exercise, both tape conditions resulted in similar changes in the FL-angle relations.