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  • Author or Editor: Deric D. Picton x
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In this study, 11 species, hybrids, and color variants were characterized using randomly amplified polymorphic DNA (RAPD) analysis. Total genomic DNA was extracted using a 2% CTAB extraction buffer using fresh or frozen leaf material. The DNA was amplified using standard RAPD-PCR protocols utilizing 10-mer primers. All primers utilized exhibited a high degree of polymorphism in their banding patterns among the species and hybrids studied. The primers used produced ≈40 reproducible bands. It was possible to identify and uniquely distinguish all species and hybrids investigated using these bands.

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Powdery mildew (Sphaerotheca mors-uvae) severely infects young shoots and leaves of black currants (Ribes nigrum) and red currants (R. rubrum) in the Pacific northwestern U.S. Environmentally sound control measures are being sought as alternatives to sulfur or demethylation-inhibiting fungicides. This study examined the effect of mineral oil spray on powdery mildew infection in susceptible black and red currants. Mineral oil at 8 mL·L-1(8000 ppm) was applied to plants until runoff at 0-, 2-, and 4-week intervals from April through June in 1999 and 2000 on eight currant cultivars growing in Corvallis, Ore. Shoot and leaf surfaces were rated for powdery mildew incidence in early July both years. Oil applications significantly reduced mildew severity in vegetative growth as compared with that of the unsprayed control. The disease control from 2-week interval and 4-week interval oil applications was not significantly different.

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Powdery mildew (Sphaerotheca mors-uvae) severely infects young leaves and stems of gooseberry (Ribes uva-crispa) throughout the world. Environmentally friendly control measures are being sought as alternatives to sulfur or demethylation inhibiting fungicides. This study examined the effect of a mineral oil spray, the biological control agent Trichoderma harzianum Rifai strain T-22 (Trichoderma), a combination mineral oil + Tricoderma, and the chemical fungicide thiophanate, on powdery mildew severity in `Industry,' a susceptible gooseberry. Mineral oil at 8 mL·L-1 (1.0 fl oz/gal), Tricoderma at 4 g·L-1 (0.5 oz/gal) and thiophanate at 1.45 mL·L-1 (0.186 fl oz/gal), and mineral oil + Tricoderma mix was applied to plants until runoff at 2-week intervals from February 2002 through April 2002, on potted `Industry' plants growing in a greenhouse in U. S. Department of Agriculture, Agricultural Research Service, National Clonal Germplasm Repository (NCGR), Corvallis, Ore. The percent of infected leaves per plant were calculated and the percent of infected stem surface areas were visually rated in mid-April. The fungicide, mineral oil, and mineral oil + Tricoderma treatment applications significantly reduced powdery mildew severity inboth leaves and stems as compared with those of the unsprayed plants. The stem powdery mildew reduction levels of the mineral oil or a combination of mineral oil + Trichoderma treatments, were not statistically different than that of thiophanate, which is reported as commercially acceptable. We recommend mineral oil spray, or mineral oil + Tricoderma, as alternatives to fungicide control of powdery mildew on leaves and stems of young gooseberry plants.

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