Early studies were often hampered by tissue browning caused by oxidation of polyphenolics due to wounding during in vitro culture establishment (Dobránszki and Teixeira da Silva 2010). The most frequently used explants in Stage 1 in apple in vitro propagation are shoot tips or axillary buds when propagated by axillary or terminal buds, or leaves when propagation is based on adventitious shoots (Fig. In vitro propagation of apple generally includes four stages, as in other plant species: (1) establishment of in vitro cultures from in vivo plants (2) shoot regeneration and/or multiplication (3) rooting of microshoots (4) acclimatization of in vitro plantlets and the establishments of plant in an in vivo environment. Tissue culture thus continues to play an essential part of apple molecular breeding (Peil et al. In vitro culture may induce genetic variations, and thus an assessment of genetic stability is required for in vitro-based methods such as cryopreservation of plant germplasm, including apple (Wang et al. This is an important issue as Webster and Jones ( 1989) discovered that increased cyclic shoot multiplication over a 21-month period induced rejuvenation of the in vitro cultured shoots of apple rootstock M9. Epigenesis may lie at the heart of somaclonal variations that can arise spontaneously in vitro as a result of long-term culture or acclimatization (Gulyás et al. One possible cause may be that a high proportion of the genome (57%) has transposable elements (Daccord et al. In addition, bagging of fruits of a triploid cultivar ‘Mutsu’ was reported to induce epigenetic changes, as indicated by increases or decreases in DNA methylation and modifies levels of acetylation and trimethylation of histone proteins (Bai et al. This updated review will allow novices and established researchers to advance apple and Malus biotechnology and breeding programs.Įpigenetic mutations can arise from the graft, resulting in altered fruit peel color (El-Sharkawy et al. ![]() The use of the plant growth correction factor allows hypothetical shoot production from leaf-derived thin cell layers relative to conventional leaf explants to be determined. Existing studies have revealed the molecular mechanism underlying the inhibition of adventitious roots by cytokinin. Several notable or curious in vitro culture methods have been reported to improve shoot regeneration and induce the production of tetraploids in apple cultivars and rootstocks. Increasingly complex molecular studies that are examining the apple genome, for example, in a bid to identify the cause of epigenetic mutations and the role of transposable elements in this process would benefit from genetically stable source material, which can be produced in vitro. This updated review presents a synthesis of findings related to the tissue culture of apple and other Malus spp. ![]() In vitro tissue culture is a biotechnological technique that has been used to genetically improve cultivars (scions) and rootstocks. Rosaceae) is an important fruit crop grown mainly in temperate regions of the world. In the past 8 years, over 100 papers advancing basic biology, genetic transformation and cryobiology have emerged.Īpple ( Malus × domestica Borkh. Studies on the tissue culture of apple have allowed for molecular, biotechnological and applied breeding research to advance.
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