Regeneration of androgenic embryos in apple (Malus x domestica Brokh.) via anther and microspore culture

Abstract

Fed eral Cen tre for Breed ing Re search on Cul ti vated Plants, In sti tute of Fruit Breed ing, Key words: Malus x domestica Borkh., an ther culture, microspore cul ture, ploidy level, re gen er a tion Ab stractBased on op ti mized pro to cols for an ther and microspore culture in ap ple (Malus x domestica Borkh.), the re gen er a tion phase and the ef fi ciency of the pro cesses in gen eral were compared by us ing the same androgenic ma te rial of two ex per imen tal years. Microspore cul ture re sulted in an in crease in embryo in duc tion de pend ing on the ge no type (Höfer 2004), however an ther cul ture was su pe rior to microspore cul ture in the to tal num ber of re gen er ated plants. The re gen er a tion pro cess in an ther and microspore cul ture is sim i lar. Two de vel op mental path ways were ob served: 1) sec ond ary embryogenesis followed by ad ven ti tious shoot for ma tion and 2) di rect ad ven titious shoot for ma tion from pri mary em bryos. In duc tion and regen er a tion pro cesses are de layed in microspore cul ture as com pared with an ther cul ture. The rea sons for the re duced regen er a tion ef fi ciency in microspore cul ture are dis cussed. In tro duc tionMost tem per ate fruit trees are char ac ter ized by a long re pro duc tive cy cle with sev eral years of a juve nile phase, a ten dency to allogamy and a large tree size. They are gen er ally highly het ero zy gous, outbreeding spe cies, which are asex u ally prop agated. For these rea sons, their ge netic im prove ment by con ven tional meth ods is time-con sum ing and lim ited by space for field ex per i ments. The pro duction of hap loids of fers new pos si bil i ties for genetic studies and breeding.Whereas the pro duc tion of dou bled hap loids reached very good re sults in many crop plant species (Maluszynski et al. 2003), fruit spe cies be long fur ther more to re cal ci trant spe cies in hap loid produc tion. Ei ther the plant re gen er a tion fails af ter induc tion of cal lus or em bryos (Arrillaga et al. 1995, Peixe et al. 2004 or the ef fi ciency of plant pro duction is very low Chiancone 2003, Kadota andNiimi 2004). Un til now, an ther cul ture has been mainly used. Be side ap ple the only attempt to ap ply microspore cul ture is the in duc tion of em bryos in Cit rus clementina (Ramirez et al. 2003).The Fed eral Cen tre for Breed ing Re search, In stitute of Fruit Breed ing has in ves ti gated hap loid induc tion in ap ple for many years. An ther cul ture tech niques were de vel oped and op ti mized (Höfer 1995(Höfer , 1997, and the first in duc tion of embryogenesis and plant for ma tion from iso lated ap ple micro spores was re ported (Höfer et al. 1999). By op ti mi za tion the pre treat ment con di tions, car bon source con cen tra tion and microspore den sity, the ef fi ciency of the in duc tion phase was im proved and 709

Apple (Malus spp.) Breeding: Present and Future

“…Higher embryogenesis has been reported for microspore culture in the apple cvs. Remo, Rene and Realka than in anther culture although not correspondent in the regeneration phase (Höfer 2004(Höfer , 2005.…”

“…These tissue culture protocols have been used in most of fruit trees with different objectives (Fig. 1.2) (Deberegh and Zimmerman 2002;Magyar-Tábori 2010;Sedlak and Paprstein 2016;Xu et al 2008), such as commercial propagation of elite rootstocks and cultivars (Sarwar and Skirvin 1997;Yepes and Aldwinckle 1994) production of stock for propagation of new obtentions from breeding programs; for genetic transformation (Krens et al 2015); for production of haploids to overcome some problems related with apple long reproductive cycle, a long juvenile phase, and highly heterozygous (Höfer 2005); or eradication of viruses (Lizarraga et al 2017;Parstein et al 2008); cryopreservation of genetic resources and development of synthetic seeds (Dobránszki and Teixeira da Silva 2010).…”

Rapid Introgression of the Fusarium Wilt Resistance Gene into an Elite Cabbage Line through the Combined Application of a Microspore Culture, Genome Background Analysis, and Disease Resistance-Specific Marker Assisted Foreground Selection

“…Mejza et al (1993) regenerated wheat plants from isolated microspores using an ovary co-culture. Although fruit species are considered to be recalcitrant to DH production, some progress has been made with apple ( Malus domestica Borkh; Hofer, 2005). However, there are few reports describing the combined use of microspore cultures and BC breeding.…”

Isolated microspore culture techniques and recent progress for haploid and doubled haploid plant production

“…Although fruit species are considered to be recalcitrant to DH production, some progress has been made with apple (Malus domestica Borkh.). Höfer (2004Höfer ( , 2005 compared anther and isolated microspore culture of apple and found that the total number of regenerated plants was higher from anther culture, even though embryo induction was higher in microspore cultures of some genotypes. Microspore induction and regeneration were also slower in microspore cultures than anther cultures.…”