Seeds no more
breeding pipless apples had been a challenge for researchers so far. But not any more. Ken Tobutt and his team at the Horticulture Research International in East Malling, usa , hope to harvest the first pipless apple by the year-end. The team has produced coreless hybrids by crossing old favourites such as Red Pippins with several obscure seedless varieties from America ( New Scientist , Vol 155, No 2097).
Both varieties are sour, seedless and have only a trace of a core. The researchers are now trying to cross the sour apples with sweeter types and produce marketable pipless apples. It took a long time for Tobutt and his colleagues to produce the seedless apples since the gene responsible for seedlessness is recessive, and plants must have two copies of it to exhibit seedlessness. If the naturally seedless varieties are crossed with normal apple variety with the gene for seed production, the resulting offspring will produce normal fruit with seeds.
However, if these trees are crossed again with the seedless varieties, half of the next generation will carry two copies of the recessive seedless gene. Each generation takes at least five years to flower, so the two-generation process takes at least a decade.
According to Tobutt, it is easy to spot seedless trees: their flowers have no petals or stamens (the male reproductive organs that produce pollen). These can be used only as female parents as they do not produce pollen and thus require hand pollination.
The growers of the seedless varieties will have to depend less on good weather during flowering. They would benefit from more regular cropping. Apple seeds produce hormones that repress future development of flower buds, so a seedless variety should flower and produce fruit every year.
During their study, the researchers have also crossed the two seedless varieties with an unusual variety of McIntosh, an apple popular in North America. McIntosh grows straight upwards and it does not have branches. This is why these trees may also be grown close to each other and require less space. The team is now seeking funds to carry research that would help pinpoint the seedless gene in order to assist the breeding programme.