A galactomannan-driven enhancement of the in vitro multiplication rate for the Marubakaido apple rootstock (Malus prunifolia (Willd.) Borkh) is not related to the degradation of the exogenous galactomannan

Meta-Topolin as an Effective Benzyladenine Derivative to Improve the Multiplication Rate and Quality of In Vitro Axillary Shoots of Húsvéti Rozmaring Apple Scion

In vitro mass propagation of apple plants plays an important role in the rapid multiplication of genetically uniform, disease-free scions and rootstocks with desired traits. Successful micropropagation of apple using axillary shoot cultures is influenced by several factors, the most critical of which is the cytokinin included in the culture medium. The impact of medium composition from single added cytokinins on shoot proliferation of apple scion Húsvéti rozmaring cultured on agar-agar gelled Murashige and Skoog medium fortified with indole butyric acid and gibberellic acid was investigated. The optimum concentration for efficient shoot multiplication differs according to the type of cytokinin. The highest significant multiplication rate (5.40 shoots/explant) was achieved using 2.0 μM thidiazuron while the longest shoots (1.80 cm) were observed on the medium containing benzyladenine at a concentration of 2.0 μM. However, application of either thidiazuron or benzyladenine as cytokinin source in the medium resulted in shoots of low quality, such as stunted and thickened shoots with small leaves. In the case of benzyladenine riboside, the 8 μM concentration was the most effective in increasing the multiplication rate (4.76 shoots/explant) but caused thickened stem development with tiny leaves. In the present study, meta-topolin was shown to be the most effective cytokinin that could be applied to induce sufficient multiplication (3.28 shoots/explant) and high-quality shoots along with shoot lengths of 1.46 cm when it was applied at concentrations of 4 μM. However, kinetin was the least active cytokinin; it practically did not induce the development of new shoots. The superior cytokinin for in vitro axillary shoot development of apple scion Húsvéti rozmaring with high-quality shoots was the meta-topolin, but it may be different depending on the variety/genotype under study.

In vitro tissue culture of apple and other Malus species: recent advances and applications

Studies on the tissue culture of apple have allowed for molecular, biotechnological and applied breeding research to advance. In the past 8 years, over 100 papers advancing basic biology, genetic transformation and cryobiology have emerged. Apple (Malus × domestica Borkh.; Rosaceae) is an important fruit crop grown mainly in temperate regions of the world. In vitro tissue culture is a biotechnological technique that has been used to genetically improve cultivars (scions) and rootstocks. This updated review presents a synthesis of findings related to the tissue culture of apple and other Malus spp. between 2010 and 2018. 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. 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. Existing studies have revealed the molecular mechanism underlying the inhibition of adventitious roots by cytokinin. 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. This updated review will allow novices and established researchers to advance apple and Malus biotechnology and breeding programs.

Why Do Plants Convert Sitosterol to Stigmasterol?

A direct role for cholesterol signaling in mammals is clearly established; yet, the direct role in signaling for a plant sterol or sterol precursor is unclear. Fluctuations in sitosterol and stigmasterol levels during development and stress conditions suggest their involvement in signaling activities essential for plant development and stress compensation. Stigmasterol may be involved in gravitropism and tolerance to abiotic stress. The isolation of stigmasterol biosynthesis mutants offers a promising tool to test the function of sterol end products in signaling responses to developmental and environmental cues.