Agriculture Reference
In-Depth Information
the surrounding somatic cells could develop into multicellular masses as compared
to only 5 % of microspores away from the wall (Chen
1986
). Anther wall callusing
is regarded as a pre-requisite for the formation of androgenic haploids (Chaturvedi
et al.
2003
; Chen et al.
1982
; Chen
1986
).
3.6.2 Microspore Culture Density
The culture density is a critical factor in isolated pollen culture. Huang et al. (
1990
)
made a detailed study on the effect of culture density on embryogenesis in pollen
cultures of
Brassica napus
. According to this report, the minimum density required
for embryogenesis is 3000 pollen/ml of the culture medium but highest embryo
yield was obtained at 10,000 to 40,000 pollen/ml.This high plating density is crucial
only for the initial couple of days. Dilution of the density from 30,000-40,000 to
1,000 pollen after two days of culture did not reduce the embryogenic frequency.
Arnison et al. (
1990
) reported the effect of culture density in anther cultures of
B.
oleracea
. The frequency of pollen embryogenesis was enhanced if the anther cul-
ture density was increased from three anthers per 4 ml to 12-24 anthers per ml of
the medium. Cardy in
1986
reported that in
B. napus
, the response was better when
anthers were cultured at a density of two anthers per ml.
3.6.3 Effect of Female Flower Position
Position of female flowers on the plant stem affected induction of embryos from
ovule cultures of
Cucurbita pepo
L (Shalaby
2007
). One of the possible explana-
tions for enhancing responses of tissue culture could be attributed to indigenous
hormonal level (Johansson
1986
).
4 Haploid Production in Economically Important
Dicotyledonous Species
4.1 Azadirachta indica A. Juss (Family: Meliaceae)
Azadirachta indica
A. Juss, commonly referred to as neem, is an adaptable, trop-
ical, evergreen tree of the family Meliaceae. It thrives best in hot, dry climates
where shade temperatures often reach 50 °C and annual rainfall ranges from 400
to 1,200 mm. The neem plant is a native of South and Southeast Asia and grows
well in tropical and subtropical areas of the world. The plant is well known for
its numerous medicinal, agrochemical and economic uses, which can be attributed
to the presence of azadirachtin, a highly oxidized limonoid (triterpenoid) found
prominently in the seed kernels. It possesses insect repellent, antifeedant, larvicidal,
