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Ladina, a new high-quality apple variety with low susceptibility to fireblight and mildew, has been developed by a Swiss research station. The variety is also scab resistant. Ladina, bred at the Swiss federal research institute Agroscope­ ­Changins-Wädenswil, comes from a cross of Topaz and Fuji made in 1999. The fruit is medium sized, and the skin is red over a green-yellow background. The flesh is crisp with good texture, and the flavor is described as subacid to sweet with an exotic note. It matures about two weeks after Gala. The tree is medium in size with a compact growth and produces good and regular yields.

The variety is in the process of being introduced, according to Agroscope apple breeder Dr. Markus Kellerhals. “We are following a stepwise procedure of introduction with further tests related to production, fruit quality, storage, and consumers, as well as market acceptance,” he said. Ladina and other advanced selections from the institute have been planted in trials in four locations in Switzerland. Ladina is also being tested in Germany, Austria, Italy, Belgium, and the Netherlands. The marketing partner VariCom is planting more pilot orchards in Switzerland with private growers, Kellerhals said.

Propagation of trees will be organized by VariCom based in Germany. Virus-free material is available.

Fruit quality

Researchers at Agroscope Changins-Wädenswil believe that planting resistant varieties could be the most promising strategy for controlling fireblight, particularly in organic production. However, classic apple breeding of resistant cultivars has been a time-consuming process because of the need to grow the trees and evaluate fruit.

A complication has been that while the crab apples Malus robusta 5 and Evereste make good parents for breeding because of their virtual immunity to fireblight, they are small with poor fruit quality. The Swiss researchers have back crossed such crab apples with high-quality cultivars over several generations to eliminate most of the negative fruit traits of the crab apples while maintaining the resistance. Moreover, they also used partially resistant cultivars such as Enterprise and Rewena in crosses. By performing crosses, multiple ­disease resistances against fireblight, apple scab and powdery mildew can be combined.

Most existing scab-resistant apples carry only the scab resistance Vf derived from the crab apple Malus ­floribunda 821. In recent years, new races of the apple scab organism have been able to overcome that resistance. In their breeding program, the Swiss researchers are combining the Vf resistance with the resistance of the Russian seedling R12740-7A (Vh2, Vh), in a process known as resistance pyramiding, to provide more durable resistance.

They use genetic markers for the diseases to quickly assess progeny for resistance. Although a relatively small number of progeny prove to have the multiple disease resistances together with high fruit quality, the scientists do have some promising selections.

The researchers say that the use of new types of genetic markers, more efficient screening methods, and genetic markers for other traits such as fruit quality and yield would help them in their quest for high-quality ­disease-resistant varieties.

Fireblight workshop

The 13th International Fire Blight Workshop of the International Society for Horticultural Science will be held in Zurich, Switzerland, July 2-5. The meeting will cover all aspects of fireblight research, including host and pathogen genetics and genomics, disease epidemiology and ecology, pathogen identification, resistance breeding, chemical and biological control, and disease management strategies.

For information, e-mail Fabio Rezzonico at fireblight2013@agro scope.admin.ch.