Malus sieversii

M. sieversii has the capability to reproduce vegetatively as they form root suckers, or basal shoots.[5] The clonal individual grows from the adventitious bud on the root, with identical genetic materials to the mother plant.[5] It was originally believed that wild apples produce root suckers only when upper plant parts are damaged.[5] However, more evidence suggested root-sucker growth occurs in healthy plants as a dispersal aid.[5]

For wild apples, proper development of root suckers requires certain humidity and aeration levels in the surface soil, where the mother root is located. Successful root-sucker growth also depends on shoot arrangement, time of growth and health conditions of the mother plant.[5]

Genetics of self-incompatibility, the system for preventing self-fertilization in angiosperms, have also been studied for M. sieversii.[9] Its genetic diversity in relation to self-incompatibility is substantially less when compared to its close relative, Malus sylvestris.[9] Although M. sieversii lacks this diversity, it can survive in the wild without intervention as long as no more diversity loss occurs.[9] The leading theory for this lack of diversity is due to a major population bottleneck during the Last Glacial Maximum which caused wild M. sieversii populations to scale back into a smaller area within the Yili Valley.[9][10]

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.[11] Fruit traits including crispness, more flavour intensity and fruit weight have undergone differential selection by humans to produce Malus domestica as seen today.[12] The dispersal of M. sieversii and its progeny throughout history can be attributed to the Silk Road.[13] A DNA analysis in 2010 confirmed M. sieversii as the progenitor of the cultivated apple.[14] 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.[15]

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.

These and other Malus species have been used in some recent breeding programmes to develop apples suitable for growing in harsh climates unsuitable for M. domestica, mainly for increased cold tolerance.[17] A study in 2020 has discovered various gene inserts involved in dormancy and cold resistance features, such as heat shock proteins, in wild apples.[15] In addition, desirable traits such as late flowering, early fruit maturity, short juvenility and stooling capability were studied by many breeding programs.[18]

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. For instance, wild apples were found to have multiple blue mold resistant genes, specifically against Penicillium expansum.[19] The USDA Plant Genetic Resources Unit (PGRU) also conducted phenotypic analysis on M. sieversii seedlings, and has identified various pathogenic resistance including apple scab, fire blight, and cedar apple rust.[20] A research in 2001 found various insect resistances within M. sieversii seedlings, and has identified instances for further research on its resistance for apple maggots and apple leaf curling midges.[13] Effects of heat on M. sieversii were also studied in hot and arid regions, and they were found to be considerably drought tolerant and sunburn resistant.[13][21]

Malus sieversii has been designated as second conservation priority in the China Plant Red Data Book, and has been marked as vulnerable by the International Union for Conservation of Nature (IUCN).[26]

Human activities and natural disasters are the major contributors to the decline of M. sieversii natural population.[5] Fungal pathogens, such as Phytophthora plurivora and Alternaria alternata, also play a major role in the decline of M. sieversii populations, by degrading vegetative parts such as the fine root systems.[27][28] This immune vulnerability makes M. sieversii become susceptible to more parasites, such as pathogenic insects Agrilus mali, to further destroy the population.[27][29]

Ex situ conservation, or seed banking, is believed to be a feasible long-term resolution to protect its genetic diversity, and has been seen in the United States using seeds collected from Kazakhstan and thee Kyrgyz Republic.[7][20] In situ conservation was also found with barbed wire fences being placed around regions distributed with M. sieversii, as seen in areas within Xinyuan, China.[7] A study in 2016 has shown the effectiveness of protecting M. sieversii populations in situ through stratification and seed coat removal.[7] Also, in situ enclosures are more effective in higher elevations as they are at less risk of human and insect injuries.[7]

Aside from traditional conservation methods, biofertilizer has shown effective results inhibiting fungal pathogen, Alternaria alternata in wild apple trees. It does this by improving antioxidant capability of wild apple trees following the infection, promoting root growth and enhancing soil metabolism.[28] Recently, a combination of innovative methods including cloning and plant hormone treatment has also shown effective results in regenerating wild apple populations.[29]

Wild apple trees were heavily lumbered for economical and agricultural uses in the mountains of Kazakhstan during the 1800s.[5] Wild apple forests were turned into pastureland, which greatly changed the soil covering, and damaged young seedlings and roots.[5] Prickly shrubs, such as eglantine and barberry exhibiting symbiotic relationships with wild apples by shielding them from predators were also cut.[5] This further worsened the growing condition for wild apples, and severely weakened root suckers and therefore vegetative propagation.[5]

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  Malus sieversii trees in Zhongar-Alatau National Park
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  A tree in Berlin-Dahlem Botanical Garden in autumn
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  Fruit

• World Conservation Monitoring Centre (1998). "Malus sieversii". IUCN Red List of Threatened Species. 1998. Retrieved 11 May 2006.old-form url Listed as Vulnerable (VU B1+2c v2.3)

Wikimedia Commons has media related to Malus sieversii.

• Wild apples in Kazakhstan: 1995 and 1996 US Agricultural Research Service expeditions
• http://www.findarticles.com/p/articles/mi_m1134/is_8_110/ai_79051530
• Malus sieversii Archived 2015-05-07 at the Wayback Machine