The use of resistant varieties in apple-tree planting

Insufficient resistance of apple tree varieties to the fungal disease - apple scab (Venturia inaequalis Cke. Wint.) is a global problem. One solution is to use resistant varieties for establishing or re-grafting apple tree plantings. In co-operation with Czech breeding institutes and stations (Research and Breeding Institute of Pomology (VSUO) Holovousy, Institute of Experimental Botany of the Czech Academy of Sciences (UEB CAV) Strizovice, Breeding Station Techobuzice-Litomerice) plantings have been established, re-grafted and evaluated using resistant varieties. In addition to the Czech resistant varieties, the first plantings established more than 15 years ago as experimental apple-tree plantings in Dolni Loucky, Jinacovice, Buchlovice and ¦abcice included varieties of the world assortment (Florina, Liberty, McFree, Priam, Primula, Priscilla, Sir Prize). At the same time a collection of the varieties Realka, Reka, Rene, Releta, Rewena, and the varieties from VSUO Holovousy, UEB Strizovice and from Kostelec nad Orlici (supplied by the breeder, Mr ¬erveny) were evaluated. The varieties were planted on rootstocks M4, M7 and M9. The variety Rubin was used as the control variant. The next step was evaluation of the resistant varieties after re-grafting. The experiment was established using the 10-year-old free growing stunted Golden Delicious and Spartan varieties, grown on rootstocks M1, M11 and A2 with inter-grafting M9. The growth properties (increment length, crown volume and harvest data) were monitored in individual years. Laboratory analysis was focused on the determination of mineral elements in fruit (P, K, Ca or Mg content) and the content of vitamin C in stored fruit. The increment length of the respective rootstock combinations and varieties was affected by harvest data. The increment length values of the Priam, Liberty and Florina varieties were very high and a number of shoots was greater than in the control. The number of the Florina variety shoots increased by 14.20%. The highest harvest data were recorded in the varieties of the world assortment, namely Prima, Florina and Sir Prize. The domestic resistant varieties (Selena, Melodie, Karmina and Angold) were characterised by high fertility. There were differences in the content of respective elements. The varieties Nabella and Resista had a high content of phosphorus, and the variety Resista showed a high concentration of potassium and calcium. The highest content of vitamin C was found in the varieties Melodie, Sir Prize and Resista (mg/100 g flesh)