Agriculture Reference
In-Depth Information
this barrier among wide hybridizations in a wide range of plant species (Collins
and Grosser
1984
). In addition, embryo rescue has been used to recover maternal
haploids that have developed as a result of chromosome elimination following in-
terspecific hybridization.
3 Factors Affecting Haploid Production
There are numerous endogeneous and exogeneous factors that affect in vitro hap-
loid production. These factors can be genetic, physiological, physical and chemical
may also interact amongst each other to divert the microspores/egg cells to enter
into a new developmental pathway. Some of the crucial factors affecting haploid
production in plants are discussed below:
3.1 Genotype of the Donor Plant
The genotype of the donor plants has great influence on anther culture response
and has been known since the early days of development of plants from pollen
grains (Nitsch and Nitsch
1969
; Maheshwari et al.
1980
). However, it is only in
recent times that the genetic factors affecting androgenesis have been studied more
intensively. Many crop species are quite recalcitrant in their in vitro response which
is governed by specific genes on the chromosomes (Datta
2005
). Certain regions
of the chromosomes appear to be associated with the formation of embryo like
structures (Wan et al.
1992
). As has been mentioned by Zhou in 1996, additive
gene effects explain most of the variations observed across diverse genotypes, but
cytoplasmic influences and non additive gene effects also play important roles in
determining in vitro regeneration ability of anther-derived cultures. In earlier stud-
ies, significant difference in callus formation using varieties or crosses was ob-
served. In some species, only a few genotypes have responded of the many that
were tested. In fact, genetic factors contribute in a major way to the differences in
the number of haploid plants produced (Custodio et al.
2005
; Sopory and Munshi
1996
).
As in anther culture, a difference in response also exists among donor cultivars in
ovary and ovule culture. It was reported by Zhu et al. (
1981
) that the percentage of
ovaries producing gynogenic calli in four wheat cultivars varied from 1.3 to 10.9 %.
In
Nicotiana tabacum
, two cultivars had an induction frequency as high as 75 %
and 80 %, but in another species,
N. rustica
, it was only 8 % (Wu and Chen
1982
).
Similar genotypic competence for gynogenesis has been reported in a number of
crop species (Keller
1990
; Lux et al.
1990
; Tosca et al.
1999
; Kobayashi et al.
1993
;
Sibi et al.
2001
; Alan et al.
2004
). It has been observed that genotypic competence
exists even between different cultivar types within the same plant species, as has
been reported in
Guizotia abyssinica
(Bhat and Murthy
2007
).
