Resistance toEntomosporium mespiliamong cultivars of saskatoon,Amelanchier alnifolia

Abstract

Saskatoon (Amelanchier alnifolia Nutt.) cultivars were evaluated for their resistance to Entomosporium leaf and berry spot disease, caused by the fungal pathogen Entomosporium mespili DC. (Sacc.). Leaves and fruit from naturally infected plants of saskatoon cultivars were evaluated for disease incidence and severity. Detached leaves of these cultivars were also evaluated for disease severity after inoculation with a conidiospore suspension under controlled conditions. Leaf age was an important factor in disease response of detached leaves, with older leaves generally displaying reduced susceptibility. Comparisons of disease response for inoculated and naturally infected leaves of various cultivars revealed similar rankings and significant correlation coefficients. Analysis of data from all experiments revealed significant differences (P ≤ 0.05) in disease response among saskatoon cultivars. Leaf disease response of saskatoon cultivars to E. mespili was classed into four groups: (1) those that restricted infection and sporulation, e.g., Success; (2) those that restricted sporulation, e.g., Regent; (3) those that reduced sporulation, e.g., Northline; and (4) those that reduced neither infection or sporulation, e.g., Pearson II. Most cultivars had moderate to high values for the incidence and severity of leaf and fruit infection. Resistant cultivars were distinguished by their ability to restrict fungal sporulation on leaves and fruit. Among the saskatoon cultivars evaluated in this study, Parkhill, Regent, and Success showed consistently lower values for the incidence and severity of fungal sporulation on leaves and fruit.Résumé : La résistance à la tache des feuilles et des fruits causée par le champignon pathogène Entomosporium mespili DC. (Sacc.) a été évaluée chez des cultivars d'amélanchier à feuilles d'aulne (Amelanchier alnifolia Nutt.). La fréquence et l'intensité de la maladie ont été évaluées sur des feuilles et des fruits d'amélanchiers naturellement infectés. L'intensité de la maladie a aussi été évaluée sur des feuilles détachées de ces cultivars après inoculation avec une suspension de conidiospores en conditions contrôlées. L'âge des feuilles fut un facteur important en ce qui concerne la réponse des feuilles détachées à la maladie, les plus vieilles feuilles montrant habituellement une sensibilité moindre. Des comparaisons entre divers cultivars quant à la réponse à la maladie des feuilles inoculées et celle des feuilles infectées naturellement ont révélé des classements similaires et des coefficients de corrélation significatifs. L'analyse des données de toutes les expériences a révélé des différences significatives (P < 0,05) entre les cultivars d'amélanchier en ce qui a trait à la réponse à la maladie. Les cultivars d'amélanchier furent classés en quatre groupes en fonction de la réponse des feuilles à la maladie : (1) ceux restreignant l'infection et la sporulation, p. ex. Success, (2) ceux restreignant la sporulation, p. ex. Regent, (3) ceux réduisant la sporulation, p. ex. Northline, et (4) ce...

Leaf-wetness duration and temperature required for infection of saskatoon leaves byEntomosporium mespiliunder controlled conditions

“…However, the specific temperature and leaf-wetness conditions required to promote E. mespili development on saskatoon plants are not known. Moreover, a recent study has indicated that disease development depends on leaf age, in that young saskatoon leaves are more susceptible to infection than older leaves (Ronald et al 2001) and, therefore, the effect of leaf age on disease development in relation to temperature and leaf-wetness duration is also not understood. In this context, the objectives of this study were: (1) to quantify the temperature and leaf-wetness durations required for causing entomosporium leaf and berry spot on saskatoon plants, and develop a regression equation for this relationship and (2) to identify the temperature and leafwetness conditions that provide optimal lesion development on young versus old leaves.…”

Infection process ofEntomosporium mespilion leaves of saskatoon,Amelanchier alnifolia

“…Buffalo. In general, all leaves of resistant cultivars and older leaves of susceptible cultivars were observed to have fewer acervuli (Ronald et al 2001). …”

“…Buffalo showed significantly higher levels of infection and sporulation than cv. Success (Ronald et al 2001).…”

“…A conidiospore suspension of E. mespili (concentration: 8 × 10 4 spores/mL) was prepared as previously described (Ronald et al 2001). Inoculum was atomized onto the adaxial surfaces of four replicates of leaves until run-off.…”

“…Buffalo and Success following artificial inoculation and natural infection(Ronald et al 2001).Fig. 1.…”