42 Percival: Effect of Systemic Inducing Resistance and Biostimulant Materials spersed with individual trees of Malus × domestica cv. Red Deli- cious and Gala as pollinators. Golden Delicious was chosen for experimental purposes due to its sensitivity to apple scab infec- tion. Planting distances were based on 2 m x 2 m (6.6 ft x 6.6 ft) spacing. The trees were planted in 2003 and trained under the central-leader system to an average height of 1.5 m ± 0.15 m (5 ft ± 0.5 ft), with mean trunk diameters of 10 cm ± 1.2 cm (4 in ± 0.5 in) at 45 cm (18 in) above the soil level. The trial site was located at the University of Reading Shinfield Experimental Site, University of Reading, Berkshire, UK (51°43 N, -1°08W). The soil was a sandy loam containing 4%–6% organic matter, pH of 6.2, available P, K, Mg, Na, and Ca were 52.0, 659.1, 175.2, 49.4, and 2188 mg liter (0.0001, 0.005, 0.002, 0.0001, 0.03 oz per gallon), respectively. Five trees were sprayed until runoff with each product at two concentrations (Tables 1 and 2), 28 days after leaf flush (mid-May), a time when leaf mate- rial shows maximum photosynthetic performance (Kitao et al. 1998) with no visible symptoms of scab development. The low- est concentration used in Table 2 is based on manufacturer’s rec- ommended rate. Double concentration was also tested for each product. Spraying trees were left for 10 days to permit absorption and uptake of each product. By Day 10, twelve fully-expanded leaves per tree were excised from actively growing shoots and all leaf material was prepared within two hours of collection. Detached Leaf Protocol and Scab Evaluation Leaves were surface sterilized by immersing in 1% sodium hy- pochlorite for 30 seconds and then rinsed in sterile distilled wa- ter for one minute to remove sodium hypochlorite residues prior to drying on Whatman filter paper (Muhammed et al. 1996). Leaves were then placed abaxial surface down in plastic petri- dishes lined with moist (sterile distilled water) Whatman filter paper. Five plates with 12 detached leaves per plate (60 leaves per treatment) were inoculated by spraying with an axenic conidial suspension that included a mixture of races 1-5 of V. inaequalis. The fungus was grown in wick cultures on 4% malt extract at 18°C (64°F) in the dark, and conidia were collected after washing each wick culture with 10 ml (0.33 fl oz) sterile distilled water, centrifuged (2000 g, 5 min), and re-suspended in distilled water until a suspension of 106 conidia ml (0.033 fl oz) was obtained. s light intensity (Yepes and Aldwinckle 1993a). At Day 5, post inoculation the percentage of conidia that had germinated and the percentage that had formed appres- soria were determined on 100 spores from 20 leaves, 5 spores per leaf (Yepes and Aldwinckle 1993b). Leaves were decolor- ized overnight by immersing in 99% cold methanol and stained with periodic acid-basic fuchsin. Whole leaves were mounted on glass slides in glycerol and examined by light microscopy. The remaining forty leaves per treatment were assessed at Day 35 af- ter inoculation using a leaf scab severity rating on the following scale: 0 = No scab observed; 1 = less than 5% of leaf area af- fected; 2 = 5%–20% of leaf area affected with some yellowing; 3 = 21%–50% of leaf area affected, significant leaf yellowing; 4 = 51%–80% of leaf area leaves affected, severe leaf yellowing; 5 = 81%–100% of leaf area with complete leaf yellowing. All labora- tory experiments took place in 2007 and were repeated in 2008. Leaf scab severity ratings used in this study was based on UK and Ireland market standards for fungicide evaluation of scab control (Butt et al. 1990; Swait and Butt 1990). Scab severity ratings were undertaken by three independent BASIS (British Agro- chemical Standards Inspection Scheme) qualified crop protec- tion specialists based at Reading University in Reading, UK. After inoculation, all plates were sealed with a thin polythene film (Parafilm) permeable to air but not water and incubated in a growth chamber at 19°C ± 1°C (66°F ± 34°F), 16 hours light/8 hours dark photoperiod from white fluorescent tubes at 40µmol m2 Statistical Methods All data was analyzed using ANOVA and the differences be- tween means were determined using Tukey w procedure (P = 0.05) using the Genstat for Windows program 8th Edition VSN International. Back transformed pathogen severity values are presented here to ease interpretation of these data. Likewise, an arcsine transformation was applied to percentage data before statistical analysis to ensure normality of data. The 2007 and 2008 data sets were not different when compared using a t-test, therefore, values presented represent pooled data for both years. Table 1. Selected SIR and biostimulant products evaluated for the control of Venturia inaequalis on apple cv. Golden delicious under laboratory conditions. Product Water (control) PhytoGard Messenger Agri-Fos DSP Rigel Bioplex 12-4-6. Fulcrum CRV Redicrop Crop Set Superthrive Systhane Active Ingredient - Potassium phosphonate Harpin protein Potassium phosphite Salicylic acid Maxicrop Original Seaweed extract Resistim Salicylic acid derivative Betaine Seaweed + humic acid extract Molasses Natural plant compound Yucca based material with liquid fermentation products Plant hormone/vitamin complex Myclobutanil SIR = Systemic Induced Resistance Property - SIR SIR SIR SIR SIR Biostimulant Biostimulant Biostimulant Biostimulant Biostimulant Biostimulant Biostimulant Synthetic fungicide Supplier - United Agri Products Ltd, Alconbury Weston, UK EDEN Bioscience Corporation, N. Bothell, Washington, USA Orion Future Technology Ltd, Henwood House, Henwood, Ashford Kent, UK Orion Future Technology Ltd, Henwood House, Henwood, Ashford Kent, UK Orion Future Technology Ltd, Henwood House, Henwood, Ashford Kent, UK Ciba Sp Maxicrop (UK) Ltd, P.O. Box 6027, Corby, UK Mandops UK Ltd, Eastleigh, Hampshire, UK United Agri Products Ltd, Alconbury Weston, UK Banks Cargill Agriculture Ltd, St Hughs, Lincoln, UK United Agri Products Ltd, Alconbury Weston, UK United Agri Products Ltd, Alconbury, Weston, UK Urban Hydroponics, Unit 1, Back Lane, Bolton, UK Syngenta Crop Protection UK Ltd, Whittlesford, Cambridge, UK ©2010 International Society of Arboriculture
January 2010
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