The varieties of apples resistant to apple scab (Venturia inaequalis CKE.) are among the latest outcomes of breeding this fruit species not only worldwide but also in the Czech Republic. A common donor of resistance to this disease is Malus floribunda Sieb., clone 821, which has conferred the qualitative resistance based on the dominant Vf gene to a range of varieties. The objective of this article is to characterise Vf gene in a collection of new Czech apple varieties. The published primers were used for PCR evaluation of the collection of twenty Czech varieties, seventeen varieties of world assortment and six new resistant selections of Czech breeding. All varieties possessing resistance based on Vf gene had the heterozygous constitution of Vf gene (Vfvf). Segregated F 1 progeny, which was already selected by infection tests in a greenhouse, was included in the same PCR test. In all progenies recessive homozygous genotypes (vfvf) were also found that were not selected by the infection test. The higher occurrence of recessive homozygous genotypes (vfvf) was detected above all in the progenies of such parental combinations where one of the parents was a donor of quantitative resistance to apple scab.

Blažková J., Drahošová H., Hlušičková I., 2010. Tree vigour, cropping, and phenology of sweet cherries in two systems of tree training on dwarf rootstocks. Hort. Sci. (Prague), 37: 127-138.Five cultivars and four rootstocks (Gisela 5, P-HL-A, P-HL-B, and Tabel Edabriz) were evaluated on trees in fruiting stage trained like spindle and on trellis. Tree vigour was significantly related to cultivar, rootstock and to tree training. Spindles were generally more vigorous than trees on trellis with exception of cv. Kordia. In several cases special combinations of cultivar, rootstock, and method of tree training differed significantly from mean effects of the three factors. Time of flowering was significantly dependent on the cultivar and varied annually within 15 days. Time of fruit harvest was also influenced by the rootstock and in two cases mutually contradictory to the tree training method. Yields per tree were generally dependent on the cultivar. With Burlat and cv. Kordia rootstock and tree training were also important. Higher specific yields were recorded on trellis-trained trees. Remarkable in this respect were Vanda and trees of Summit on P-HL-B and Starking Hardy Giant on Tabel Edabriz. Higher specific yields on spindle had Kordia on P-HL-A and Tabel Edabriz and Burlat on P-HL-A. Mean values of annual yields per hectare in spindle ranged between 10.0 to 17.5 t whereas in trellis between 6.7 to 12.3 t. The absolute highest annual yield (35.7 t) was recorded on spindle trees of Kordia on P-HL-A. In trellis the highest yield of 27.1 t had Kordia on Gisela 5. The advantage of spindle over trellis was greater in Burlat and Kordia but much lower in cv. Vanda. Fruit size mainly depended on the year. Only two rootstocks influenced fruit size differently in some years. Training system had no effect on fruit size.

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The occurrence of powdery mildew after heavy spontaneous infections was evaluated on 2,500 apple seedlings of 54 progenies that were derived from crosses made in 1993 and 1994. At the same time, the response to mildew was also assessed on 47 cultivars or selections that were used as parents for the crosses. Scores of the strongest infestation were used for final ranking of every seedling or parent. The highest proportions (33 and 28%) of seedlings with complete resistance to mildew were attained in 2 progenies involving parents transmitting monogenic resistance to the pathogen. A few seedlings with this resistance were also found in other 7 progenies. Seedlings with partial resistance to mildew were distributed in the highest proportions (about 30%) among 7 progenies. In 6 out of these progenies, always one parent was derived from partially resistant selections that were selected in the first generation from the cross Spätblühender Taffetapfel × Court Pendu Plat. A very close relationship was found between mid-scores of parents and mean response to powdery mildew infection in progenies. Seedlings on average were significantly more infested than their parents. Progenies determined to have a columnar growth habit were somewhat less infested than progenies possessing a standard growth pattern only. This study revealed considerable improvement of some donors transmitting partial resistance to powdery mildew.