Agriculture Reference
In-Depth Information
cv Nules. The addition of 2 mM spermidine to the suggested medium of Germanà
and Chiancone (
2003
) stimulated gametic embryogenesis in 4 % cultures whereas
putrescine did not influence embryo production. Flow cytometric analysis revealed
that the regenerants were mostly trihaploids; few were doubled-haploids while none
of them were haploids.
4.5 Malus domestica Borkh. (Family: Rosaceae)
Malus domestica
Borkh. (Family: Rosaceae) or apple is an important temperate
fruit tree. It is one of the most widely cultivated tree fruits in the world. In vitro
approaches to induce haploids in apple have been rather limited in comparison
to other plant species (Höfer and Lespinasse
1996
). Anther culture in apple was
pioneered by Japanese scientists at the beginning of the 1970s. They induced calli
capable of root formation. Subsequently, several working groups initiated haploid
induction in apple by anther culture. Induction of embryogenesis and plant forma-
tion has been reported in apple from anther cultures (Fei and Xue
1981
; Xue and
Niu
1984
; Höfer
1995
). Although regeneration from embryos is reproducible via
adventitious shoot formation, the induction of embryogenesis from cultured apple
anthers is still low and highly dependent on genotype (Höfer
1995
,
1997
). Kolova
et al. (
1994
) obtained multinuclear structures and Bouvier (
1993
) obtained callus
formation from isolated microspore cultures. Höfer et al. (
1999
) reported, for the
first time, the induction of embryogenesis and plant formation from isolated apple
microspores at late uninucleate stage of development. The authors reported that
several factors were responsible for successful androgenesis in apple, especially
a combination of starvation and cold treatment. The effect of starvation of buds
or microspores for 1-2 days at 4 °C or 27 °C was found to be very important
for androgenesis in apple. Starvation is an effective stress treatment which has
yielded successful embryogenic induction in tobacco (Kyo and Harada
1986
; Tou-
raev et al.
1996a
) and wheat microspores (Touraev et al.
1996b
). The requirement
of heat or cold pre-treatment has been shown to vary from plant to plant (Höfer
et al.
1999
). The induction medium and genotype of the donor plant strongly af-
fect embryogenic capacity of isolated microspores. “Alkmene” and “Rene” are the
cultivars of apple in which the highest embryo induction via anther culture was
achieved. Success with “Rene” has been reflected in many experiments related to
androgenesis in apple. They attained 17 % embryo induction from microspore cul-
tures as compared to only 7 % induction from anther cultures on modified N
6
basal
medium devised by Chu et al. (
1990
) in wheat. The embryos were germinated on
MS + TDZ (0.45 µM). Höfer (
2004
) reported that an increase in the frequency of
embryo induction is possible up to 10 times by microspore culture depending on
the genotype. Starvation treatment, induction medium, maltose concentration, type
of culture vessel, microspore density and genotype influenced embryo induction
in apple Höfer (
2004
).
