Low hull percentage has long been recognized as a valuable measure of grain quality in oat, Avena sativa L.; however, reliable selection for low hull percentage has been impeded by a lack of understanding of its heritability. The objective of this study was to investigate the heritability of hull percentage in three oat crosses, involving the cultivars Cascade, Robert, and AC Marie, which have 30, 25, and 23% hull, respectively. Populations F2‐deriveF4 through F7 lines were grow in replicated or unreplicated trials at several locations in western Canada from 1992 to 1995. Heritability estimates were calculated based on hull percentage data determined by mechanically dehulling 2‐g kernel mixtures or samples of 50 primary kernels. Primary kernel hull percentage data, collected from replicated trials at multiple locations, were used to evaluate the effect of genotype × location interaction on phenotype. Broad‐sense heritability estimates by parent‐offspring regression ranged from 0.35 to 0.72 for hull percentage of 2‐g kernel mixtures, and 0.80 to 0.90 for hull percentage of 50 primary kernels. An evaluation of variance components showed highly significant genotype and location effects for primary kernel hull percentage. Genotype effects had a greater influence than location on primary kernel hull percentage, whereas the effect of genotype × location interaction was relatively less important. High broad‐sense heritability estimates for hull percentage support the use of early generation selection for reduced hull content in oat.

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...

Percent hull is an important physical parameter of oat grain quality, but it is affected by environment. Multiple time-consuming evaluations are required to obtain a correct determination of phenotype. The application of marker-assisted selection for the genes involved would greatly simplify the identification of desirable oat genotypes. Bulked segregant analysis, with selected progeny lines derived from a cross between Cascade and AC Marie (30 and 23% hull, respectively), was used to identify randomly amplified polymorphic DNA markers linked to genetic factors controlling primary kernel hull percentage in oat. Twelve polymorphisms, identified between bulks, were tested for linkage to genetic factors controlling hull percentage by genotyping 80 randomly selected F2-derived F8 lines from the progeny population. Three markers showed significant test statistics for quantitative trait locus effects, when tested with primary kernel percent hull data from two environments. Together, the unlinked marker loci OPC13800, OPD20600, and OPK71300 explained approximately 41% of the genetic variance in primary kernel percent hull, after accounting for the main effect of environment.

The infection process for Entomosporium leaf spot of saskatoon (Amelanchier alnifolia) was evaluated with scanning electron microscopy. Following treatment with a conidiospore suspension of Entomosporium mespili, detached leaves of saskatoon cultivars were fixed at various times during disease development (2, 5, 8, and 12 days postinoculation). Scanning electron microscopy showed that conidiospore germination occurred rapidly, usually by the extrusion of a single major germ tube from the larger of two body cells. Fungal penetration of the host cuticle involved appressoria, produced directly below the germinating spore or at germ tube termini. Subspore appressoria were most common and resulted in the earliest formation of leaf acervuli. Conidiospore germination and penetration occurred more rapidly on leaves of the susceptible cv. Buffalo, than on leaves of resistant cv. Success. At 2 days postinoculation, 43% of germinating conidiospores had penetrated the leaf surface of cv. Buffalo, compared with 12% on leaves of cv. Success. Acervuli bearing large quantities of conidiospores, were produced as the result of conidiogenesis from a subcuticular stroma of hyphae. Acervuli formed on leaves of all saskatoon cultivars, but cultivars differed in acervulus surface area and number of acervuli per leaf.Résumé : Le processus d'infection dans le cas de la tache des feuilles (causée par un Entomosporium) de l'amélanchier à feuilles d'aulne (Amelanchier alnifolia) fut étudié à l'aide du microscope électronique à balayage. À la suite d'un traitement avec une suspension de conidiospores d'Entomosporium mespili, des feuilles détachées de cultivars d'amélanchier furent fixées à différentes périodes du développement de la maladie (2, 5, 8 et 12 jours après l'inoculation). Le microscope électronique à balayage montra que la germination des conidiospores a lieu rapidement, habituellement par l'extrusion d'un tube germinatif unique à partir de la plus grosse des deux cellules somatiques. La pénétration fongique de la cuticule de l'hôte implique des appressoria qui sont produits directement sous la cellule en germination ou à l'extrémité du tube germinatif. Les appressoria sous-sporaux étaient plus communs et étaient responsables de la formation des premiers acervules sur les feuilles. La germination et la pénétration des conidiospores a eu lieu plus rapidement sur les feuilles du cultivar sensible Buffalo que sur les feuilles du cultivar résistant Success. Au jour 2 après l'inoculation, 43% des conidiospores en germination avaient pénétré la surface des feuilles de cv. Buffalo, par rapport à 12% sur les feuilles de cv. Success. Les acervules portant de grandes quantités de conidiospores furent produits à la suite de la conidiogénèse issue d'un stroma subcuticulaire d'hyphes. Les acervules se sont formés sur les feuilles de tous les cultivars d'amélanchier, mais des différences entre les cultivars furent observées quant à l'étendue de la surface et au nombre d'acervules par feuille.