Over The Horizon

Wild Apples Resistant

Wild apples from Kazakhstan may hold the key to better apple varieties for New Zealand.

HortResearch scientist Vincent Bus is seaching through apple varieties from around the world looking for genes conferring resistance to apple pests and diseases. Thousands of seeds from old apple varieties and crab apples have been grown and tested for resistance, mainly to black spot, but also for other problems such as fire blight, powdery mildew and woolly apple aphid.

Crab apples carry genes that confer immunity and, because there usually is only one gene involved, it is easy to use them for breeding. Some have been imported via France and the US, but most have their origins in Russia, China or Japan.

Eating apples are believed to have originated in Kazakhstan. HortResearch has material gathered from there during expeditions in the mid-1990s. Plants grown from seeds collected in 1993 are starting to fruit now and have already provided a number of new sources for resistance.

Of the 2,500 seed from the 1995 and 1996 Kazakhstan expeditions, about 25% have shown resistance to black spot.

Using the Kazakhstan material has major advantages. The fruit is already large and has a fair eating quality. Preliminary information shows that some of these accessions already have 3-4 resistance genes to black spot.

"The whole theme of my breeding programme is to bring different types of resistances together. There are eight or nine known major resistance genes to black spot to date, and the idea is to put different types together and make a more durable resistance," says Bus.

"It would then be a lot harder for black spot to overcome that resistance. By bringing different types of resistance together into one variety, we effectively have several weapons in one to fight disease," he says.

The next stage is to put that resistance into popular commercial varieties.