. 2009. A study of scab resistance in 16 apple progenies using parents with partial scab resistance. Can. J. Plant Sci. 89: 693Á699. A study was conducted to examine the inheritance of partial resistance to apple scab [Venturia inaequalis (Cke.) Wint.] using as parents a set of apple (Malus )domestica Borkh.) cultivars that show a range of field resistance to the disease, but are not known to carry any major-gene resistance. Akane, Alkmene, Antonovka, Carola, Chehalis, Goldgelbe, Katja and Summerred were used as pollen parents, and Spartan and an unnamed selection of Splendour )Gala parentage were used as seed parents in a factorial 2 )8 mating design. One hundred seedlings of each family were planted in a randomized complete block design at a site with heavy annual natural scab infections. Each seedling was rated for infection severity for 3 consecutive years using a six-point categorical scale. A x 2 procedure was used to estimate the contribution of each parent to field resistance (analogous to general combining ability, GCA) and the contribution of the particular male-female combination (analogous to specific combining ability, SCA). Infection severity tended to increase over the 3 yr of the study. Antonovka and Chehalis had the highest analogous GCA for resistance (defined here as absence of sporulating lesions). Specific combining ability was present in 2 of 3 yr, but was small in magnitude relative to GCA. The field resistance of a given parent tended to be a poor predictor of its breeding value. However, 13 of the 16 families had at least 30% of seedlings with a potentially useful degree of partial resistance (low severity of infection). The results are discussed in the context of breeding apples with durable scab resistance. . Ils ont utilise´pour cela les parents d'un groupe de cultivars de pommier (Malus )domestica Borkh.) affichant une re´sistance variable a`la maladie sur le terrain, mais qu'on ignorait porter ou pas d'importants ge`nes de re´sistance. Les cultivars Akane, Alkmene, Antonovka, Carola, Chehalis, Goldgelbe, Katja et Summerred ont servi a`produire le pollen qui a fertilise´la varie´teŚ partan et une se´lection sans nom d'ascendance Splendour )Gala pour la production de graines, dans le cadre d'un essai de reproduction factoriel 2 )8. Cent plantules de chaque famille ont ensuite e´te´repique´s au hasard en blocs ale´atoires complets, a`un endroit marque´par d'importantes infections naturelles de tavelure chaque anne´e. Chaque plantule a e´teń ote´e selon la gravite´de l'infection pendant trois anne´es conse´cutives, au moyen d'une e´chelle a`6 points. Une technique x 2 a permis d'estimer l'apport de chaque parent a`la re´sistance sur le terrain (valeur analogue a`l'aptitude ge´ne´rale a`la combinaison, GCA) et la contribution du couple maˆle-femelle particulier (valeur analogue a`l'aptitude spe´cifique a`la combinaison, SCA). Le degre´d'infection a eu tendance a`augmenter au cours des trois anne´es qu'a dure´es l'e´tude. Les cultivars Antonovka et Chehalis pre´sentaient la plus forte val...