Glacial Maximum which caused wild M. sieversii populations to scale back into a smaller area within the Yili Valley. Growth cycle The growth cycle of M. sieversii could be divided into several stages from germination to developing fruit bearing trees, and to the death of aged trees. Period I starts from seed germination to the development of vegetative tree parts, and to the first round of fruiting. A typical apple tree reaches age 6 to 8 in this period. Prominent primary growth and a significant number of root sucker growth are seen in this period. Period II involves more growth and fruit bearing. Wild apple trees usually reach age 10 to 12 in this period. The number of fruits increase significantly as prominent secondary growth and branching take place. Period III involves more growth and fruit bearing. Wild apple trees enter regular fruiting and reach maximum fruit bearing in this period, and usually reach age 25 to 30. Decreased branching rate, and less growth of crown periphery are seen. A lot of vegetative growth is contributed by basal shoots (root suckers). Period IV is fully fruit bearing. Development of trees fully ceases in this stage and they reach around 60 to 70 years of age. Branching decreases as they slowly die off from the base to the periphery. After age 60 to 70, trees experience rapid desiccation of the branches, then death. History and importance Malus sieversii has previously been identified as the main contributor to the genome of the cultivated apple (Malus domestica), on the basis of morphological, molecular, and historical evidence. Fruit traits including crispness, more flavour intensity and fruit weight have undergone differential selection by humans to produce Malus domestica as seen today. The dispersal of M. sieversii and its progeny throughout history can be attributed to the Silk Road. A DNA analysis in 2010 confirmed M. sieversii as the progenitor of the cultivated apple. It has a highly variable genetic diversity therefore it is the genetic source for abiotic and biotic stress tolerance, many disease resistance and unique fruit traits. Almaty, the largest city in Kazakhstan, and formerly its capital, derives its name from the Kazakh word for "apple" (Alma), and is often translated as "full of apples" (the region surrounding Almaty is home to forests of Malus sieversii); alma is also "apple" in other Turkic languages, as well as in Hungarian. The threat of extinction