BREEDING EXPERIMENTS OF APPLE VARIETIES WITH COLUMNAR GROWTH AND LOW CHILLING REQUIREMENTS

Abstract

Worldwide breeding activities take advantage of the positive attributes of columnar grown apple trees for yield efficiency, production management as well as for frost and drought resistance. For 15 years, the Pomology Section of the Geisenheim Research Center has concentrated on the breeding of columnar apple trees (CATS) and has released a number of table and processing varieties over that time. As a contribution to the improvement in apple production in warm climates, five candidate clones/varieties, from the breeding programme in Geisenheim, were crossed with the Israeli low chilling variety 'Anna' in 2003. In April 2004, approximately 500 seedlings were established in the field after temporally differentiated seed stratification. In the years 2005 to 2007 the chronological sequences of bud swelling and sprouting were evaluated. About 12% of the seedlings were low chilling candidates. The Brazilian apple variety 'Primicia' was used as a reference variety. Approximately 60% of the selected low chilling candidates were of the columnar type. In spring 2007, nearly all candidates had set flowers, so that in summer/autumn 2007, fruits of most of the candidates could be evaluated. It is expected that from this pool of candidates, some will have the desired attributes of columnar growth, low chilling requirement and good fruit quality. That achievement would mean a fundamental improvement for the apple production in warmer climates. The results will be presented at the VIII th International Symposium on Temperate Zone Fruits in the Tropics and Subtropics in Florianopolis, Santa Catarina, Brazil, in October 2007.