Plant Pathology (2002) 51, 443-453

M.H. Pei, C. Ruiz, T. Hunter, G.M. Arnold and C. Bayon (2002)
Quantitative relationships between inoculum of Melampsora larici-epitea and corresponding disease on Salix
Plant Pathology 51 (4), 443-453
Abstract: Six Salix clones were inoculated with urediniospores of four isolates of Melampsora larici-epitea at five inoculum levels using a leaf-disc method. Disease reactions were recorded using a digital camera; the number and size of uredinia were examined using image analysis software; and spore yield per leaf disc was measured. In three Salix/Melampsora combinations, S. x mollissima 'Q83'/Q1 (LET4); S. viminalis '78183'/V1 (LET1); and S. x stipularis/V1, pustule numbers increased as inoculum density became higher. In the remainder, S. viminalis 'Mullatin'/V1; S. x calodendron/DB (LET3); and S. burjatica 'Korso'/K (LR1), pustule numbers initially increased, then decreased as inoculum densities exceeded 140-360 spores per disc. Calculated infection efficiency ranged from 0·11 to 0·20 on the three willows inoculated with V1: 0·16-0·68 for S. x calodendron/DB; 0·20-0·55 for 'Q83'/Q1; and 0·07-0·48 for Korso/K. In single-spore inoculations, up to 10% of spores produced single uredinia. Infection efficiency increased sharply between inoculum densities of 1-40 spores per leaf disc. Spore yield was more closely correlated to pustule area (accounting for 61·2% variance for the combined data) than to the number of pustules (42·7% variance). For spore yields in relation to pustule numbers, clone-specific individual lines having different intercepts and slopes fitted significantly better than either a single line for all the tested willows, or parallel lines fitted to each clone (P < 0·001). For spore yields in relation to pustule area, clone-specific individual parallel lines were significantly better than a single line (P < 0·001).
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Database assignments for author(s): Ming H. Pei

Research topic(s) for pests/diseases/weeds:
general biology - morphology - evolution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Melampsora larici-epitea	Willow (Salix)	United Kingdom