Disease severity keys for powdery and downy mildews of pea, and powdery scab of potato

Abstract

Disease severity keys are described and illustrated for powdery mildew (Erysiphe pisi DC.) and downy mildew (Peronospora viciae (Berk.) Caspary) of pea (Pisum sativum L.), and powdery scab (Spongospora subterranea (Wallr.) Lagerh. f. sp. subterranea Tomlinson) of potato (Solanum tuberosum L.). The keys consist of illustrations of pea leaves or potato tubers in 11-point (0-10) severity scales of arbitrary proportions of surface areas diseased. The keys were constructed from hand drawings of pea leaflets or potato tubers, with colonies or lesions drawn to resemble typical infections of the respective diseases. Proportions of surface area of plant parts "diseased" on drawings were confirmed using computer-assisted image analysis. The drawings were then scanned into computer storage for manipulation into illustrated keys for publication. The complete keys, or abbreviated versions, have been used for assessing severity of the diseases in recent research on crop loss assessment, disease control, susceptibility assessment, and disease epidemiology. They also provide bases for accurate disease severity assessment in commercial pea and potato crops.

Powdery scab disease of potato — a review

“…Plants are grown to maturity in the presence of inoculum, usually spore balls, although zoospores have also been used (Mäkäräinen et al, 1994), in an environment that favours the disease. The tubers are harvested, cleaned and disease severity is assessed by visual inspection, sometimes with a key to improve the accuracy of assessment (Falloon et al, 1995). Roer (1983) considered that the only reliable way of determining resistance to powdery scab is to grow plants in naturally infested soil in the field in an area with a cool, wet climate.…”

Powdery scab effect on the potato Solanum tuberosum ssp.andigena growth and yield: andigena

“…Average tuber weight (g) was calculated by dividing the total tuber weight of each plot by its number of tubers. Powdery scab incidence and severity of 10 randomly chosen tubers per plot were determined by counting the tubers with pustules and using the visual scoring scale by Falloon et al (1995), respectively.…”

A Greenhouse Assay for Powdery Scab (Spongospora subterranea f. sp. subterranea) Resistance in Potato

“…In addition, in assay 1 and assay 2 the length (stolon end to apical tip) and width (perpendicular to the length at the widest point) were measured using a digital calliper (Digimatic calliper, Mitutoyo, Japan). Disease severity was assessed on an ordinal scale, adapted from Falloon et al (1995) and Merz (2000), where 0 is no disease symptoms and 7 is complete coverage of the tuber skin in lesions (Fig. 2).…”