Agriculture Reference
In-Depth Information
Biotechnology of apples
and pears
Propagation
in vitro
Propagation
in vitro
provides a method of rapid propagation of clonal plant
material. It has a number of specific uses in the production of apple and
pear plants which extend and complement the traditional means by which
these, both scions and rootstocks, are vegetatively propagated. It also provides
the reliable and efficient regeneration systems from somatic tissues that are
essential to the development of systems of transfer of individual genes in the
process of genetic engineering.
Shoot culture involves the use of explants which may be nodal buds or shoot
tips ranging from
cm. Explants are surface-sterilized, usually
by washing in solutions of sodium or calcium hypochlorite. They are then
cultured in a medium based on that of Murashige and Skoog (
.
mm to
.
), contain-
ing mineral salts, sucrose, cytokinin and possibly some auxin and gibberellin,
and solidified with agar. Sorbitol may be more effective than sucrose with
some apple cultivars and phloridzin or its breakdown product phlorogluci-
nol may increase shoot growth ( Jones,
). Shoot cultures are maintained
on the culture medium in illuminated growth rooms. Their axillary buds
extend to give new shoots which are excised at approximately monthly in-
tervals and transferred to a fresh medium where they in turn produce axil-
lary shoots. Shoot culture lines may be multiplied indefinitely by sequential
subculture.
Shoot cultures may become slow-growing with tightly-rolled translucent
leaves. This condition is known as vitrification. It involves excess water uptake
and inhibition of lignin and cellulose synthesis and is associated with low agar
concentrations and a high ratio of ammonium to nitrate.
The production of plantlets is achieved by excising shoots and transferring
them to a medium with IBA but no cytokinin in which adventitious roots are
initiated. The plantlets are then transferred to pots of compost and grown on
