Malus sieversii

Malus sieversii is a wild apple native to the mountains of Central Asia in southern Kazakhstan, Kyrgyzstan, Tajikistan, Northern Afghanistan and Xinjiang, China. It has recently been shown to be the sole ancestor of most cultivars of the domesticated apple (Malus domestica). It was first described (as Pyrus sieversii) in 1833 by Carl Friedrich von Ledebour, a German naturalist who saw them growing in the Altay Mountains.

It is a deciduous tree growing to 5-12 m tall, very similar in appearance to the domestic apple. Its fruit is the largest of any species of Malus, up to 7 cm diameter, equal in size to many modern apple cultivars. Unlike domesticated varieties its leaves go red in autumn: 62.2% of the trees in the wild do this compared to only 2.8% of the 2170 English cultivated varieties. The species is now considered vulnerable to extinction.

History and importance

For many years, there was a debate about whether M. domestica evolved from chance hybridization among various wild species. Recent DNA analysis by Barrie Juniper, Emeritus Fellow in the Department of Plant Sciences at Oxford University and others, has indicated, however, that the hybridization theory is probably false. Instead, it appears that a single species still growing in the Ili Valley, on the northern slopes of the Tien Shan mountains at the border of northwest China and Kazakhstan, is the progenitor of the apples we eat today. Leaves taken from trees in this area were analyzed for DNA composition, which showed them all to belong to the species M. sieversii, with some genetic sequences common to M. domestica.

However, another recent DNA analysis showed that Malus sylvestris has also contributed to the genome of M. domestica. A third species that has been thought to have made contributions to the genome of the domestic apples is Malus baccata, but there is no hard evidence for this in older apple cultivars.

It is named alma in Kazakhstan; the region in Kazakhstan thought to have the oldest such plants includes the city of Alma-ata, or "Grandfather of Apples".

Renewed interest

These and other Malus species have been used in some recent breeding programmes to develop apples suitable for growing in climates unsuitable for M. domestica, mainly for increased cold tolerance.

Malus sieversii has recently been cultivated by the United States Agricultural Research Service, in hopes of finding genetic information of value in the breeding of the modern apple plant. Some, but not all, of the resulting trees show unusual disease resistance. The variation in their response to disease on an individual basis is, itself, a sign of how much more genetically diverse they are than their domesticated descendants.