Malus sieversii in harsh climates unsuitable for "M. pumila", 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. Malus sieversii Malus sieversii is a wild apple native to the mountains of Central Asia in southern Kazakhstan. It has
Malus are borne in corymbs, and have five petals, which may be white, pink or red, and are perfect, with usually red stamens that produce copious pollen, and a half-inferior ovary; flowering occurs in the spring after 50–80 growing degree days (varying greatly according to subspecies and cultivar). Apples require cross-pollination between individuals by insects (typically bees, which freely visit the flowers for both nectar and pollen); all are self-sterile, and (with the exception of a few specially developed cultivars) self-pollination is impossible, making pollinating insects essential. Several "Malus" species, including domestic apples, hybridize freely. They are used as food plants