| Malus sieversii | |
|---|---|
 | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Rosids |
| Order: | Rosales |
| Family: | Rosaceae |
| Genus: | Malus |
| Species: | M. sieversii |
| Binomial name | |
| Malus sieversii | |
| Synonyms[2][3][4] | |
Malus sieversii is awild apple. According toDNA analysis conducted in 2010, it is the primary ancestor of the domesticated apple,M. domestica. Its scientific name is accredited toJohann August Carl Sievers.
Native to Central Asia,M. sieversii prefers warm and damp habitats. Its conservation status is vulnerable.
It is adeciduous tree growing 5 to 12 metres (16 to 39 ft), very similar in appearance to the domestic apple. Its pollen grains vary in size and are seen to be ovular when dry and spherical when swelled with water.[5] Itsfruit is the largest of any species ofMalus exceptdomestica, up to 7 cm in diameter, equal in size to many modernapple cultivars. Unlike domesticated varieties, its leaves go red in autumn: 62% of the trees in the wild do this compared to only 2.8% of the regular apple plant or the 2,170 English cultivated varieties.[6]
M. sieversii has the capability to reproduce vegetatively as they form root suckers, orbasal shoots.[7] The clonal individual grows from the adventitious bud on the root, with identical genetic materials to the mother plant.[7] It was originally believed that wild apples produce root suckers only when upper plant parts are damaged,[7] but further evidence suggests root-sucker growth occurs in healthy plants as a dispersal aid.[7]
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.[7]
Genetics ofself-incompatibility, the system for preventing self-fertilization in angiosperms, have also been studied forM. sieversii.[8] Its genetic diversity in relation to self-incompatibility is substantially less when compared to its close relative,M. sylvestris.[8] AlthoughM. sieversii lacks this diversity, it can survive in the wild without intervention as long as no more diversity loss occurs.[8] The leading theory for this lack of diversity is due to a majorpopulation bottleneck during theLast Glacial Maximum which caused wildM. sieversii populations to scale back into a smaller area within the valley of theIli River.[8][9]
The growth cycle ofM. sieversii could be divided into several stages from germination to developing fruit bearing trees, and to the death of aged trees.[7]
The species was first described asPyrus sieversii due to its similarities withpears in 1833 byCarl Friedrich von Ledebour, a German naturalist who saw them growing in theAltai Mountains.[7]
Malus sieversii has previously been identified as the main contributor to the genome of the cultivated apple (Malus domestica), on the basis ofmorphological,molecular, and historical evidence.[10] Fruit traits including crispness, more flavour intensity and fruit weight have undergone differential selection by humans to produceMalus domestica as seen today.[11] The dispersal ofM. sieversii and its progeny throughout history can be attributed to theSilk Road.[12] ADNA analysis in 2010 confirmedM. sieversii as the progenitor of the cultivated apple.[13] 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.[14]
Planting cultivated apple varieties close to wild groves causes crossbreeding.[15]
Malus sieversii is distributed mainly within the Ili valley in southernKazakhstan, where the damp climate suits its growth.[16][5]
It appears in many different habitats.[7] Although the species prefers high temperatures and short winters, it is also found in theTian Shan mountains which have long and harsh winters.[7]
After the collapse of the USSR and the closure of the Gardening Development Program, the local population began to actively cut down wild gardens in the Zailiyskiy Alatau. The vacated territories are used for building houses and grazing animals.[citation needed]
Malus sieversii has been designated as second conservation priority in the China Plant Red Data Book, and has been marked as vulnerable by theInternational Union for Conservation of Nature (IUCN).[17]
Human activities and natural disasters are the major contributors to the decline ofM. sieversii natural population.[7] Fungal pathogens, such asPhytophthora plurivora andAlternaria alternata, also play a major role in the decline ofM. sieversii populations, by degrading vegetative parts such as the fine root systems.[18][19] This immune vulnerability makesM. sieversii become susceptible to more parasites, such as pathogenic insectsAgrilus mali, to further destroy the population.[18][20]
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 the Kyrgyz Republic.[5][21]In situ conservation was also found with barbed wire fences being placed around regions distributed withM. sieversii, as seen in areas withinXinyuan, China.[5] A study in 2016 has shown the effectiveness of protectingM. sieversii populations in situ throughstratification and seed coat removal.[5] Also, in situ enclosures are more effective in higher elevations as they are at less risk of human and insect injuries.[5]
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.[19] Recently, a combination of methods including cloning and plant hormone treatment has also shown effective results in regenerating wild apple populations.[20]
Wild apple trees were heavily lumbered for economical and agricultural uses in the mountains of Kazakhstan during the 1800s.[7] Wild apple forests were turned into pastureland, which greatly changed the soil covering, and damaged young seedlings and roots.[7] Prickly shrubs, such as eglantine andbarberry exhibiting symbiotic relationships with wild apples by shielding them from predators were also cut.[7] This further worsened the growing condition for wild apples, and severely weakenedroot suckers and thereforevegetative propagation.[7]
These and otherMalus species have been used in some recent breeding programmes to develop apples suitable for growing in harsh climates unsuitable forM. domestica, mainly for increased cold tolerance.[22] A study in 2020 has discovered various gene inserts involved in dormancy and cold resistance features, such asheat shock proteins, in wild apples.[14] In addition, desirable traits such as late flowering, early fruit maturity, short juvenility and stooling capability were studied by many breeding programs.[23]
Malus sieversii has recently been cultivated by the USAgricultural 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 againstPenicillium expansum.[24] TheUSDA Plant Genetic Resources Unit (PGRU) also conducted phenotypic analysis onM. sieversii seedlings, and has identified various pathogenic resistance includingapple scab,fire blight, andcedar apple rust.[21] A research in 2001 found various insect resistances withinM. sieversii seedlings, and has identified instances for further research on its resistance forapple maggots and apple leaf curling midges.[12] Effects of heat onM. sieversii were also studied in hot and arid regions, and they were found to be considerablydrought tolerant and sunburn resistant.[12][25]
Malus sieversii has been recently used as a critical source in the breeding of red-fleshed apples, due to its high genetic variability. This is seen as they are used to improve the stress resistance towards drought, cold, and pests of cultivated apple species.[26] Some neglected characteristics ofM. sieversii, such as high-flavonoid contents (especiallyanthocyanin) and short juvenile phases, have recently been used for red-fleshed apple breeding since traditional red-fleshed apples are not rich in these flavonoids.[26] UsingM. sieversii for breeding due to its high anthocyanin content has numerous benefits, including preventing cardiovascular disease and protecting against liver damage.[27] The variant ofM. sieversii,Malus sieversii f. niedzwetzkyana, has been emphasized for the use of breeding red-fleshed apples since it has red flowers, fruit skin, and pulp; in addition to its high anthocyanin content.[28][27] When breedingMalus sieversii f. niedzwetzkyana, it was found that light results in higher anthocyanin production than those bred in the dark.[27] Hybrids ofMalus sieversii have also been an interest for breeders of red-fleshed apples.[29]
Almaty, the largest city inKazakhstan, and formerly its capital, possibly derives its name from theKazakh wordalma 'apple', and it is often explained as meaning 'full of apples' (the region surrounding Almaty is home to forests ofMalus sieversii).[citation needed]
{{cite journal}}: CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)Phylogenetic reconstruction of Pyreae and the genusMalus, relative to major Rosaceae taxa, identified the progenitor of the cultivated apple asM. sieversii
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