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Wheat Information
Service
Number 74: 28-32 (1992)
Studies
on pollen germination, pollen tube growth and seed set in reciprocal
wheat-barley crosses
Neeraj and V. K. Khanna
Department of Plant Breeding, G. B. Pant Agrivarsity, Pantnagar,
India.
Hordeum species have a number of agronomic traits those are
useful for improvement of wheat, such as wide geographic adaptation,
salinity tolerance, high lysine content and others. However, the
intergeneric hybrids between barley and wheat are difficult to obtain
due to disturbances in the processes of fertilization, impaired
development of hybrid embryos and endosperm degeneration (Bannicova
1975). The cross wheat x barley has been reported to be more
difficult than its reciprocal cross (Fedak 1980, Islam et al
1981).
It is well known that two dominant genes, Kr1 and Kr2
located on wheat chromosomes 5B and 5A, respectively, inhibit
crossability of wheat with rye (Riley and Chapman 1967). The dominant
alleles at these crossability loci actively inhibit the production of
intergeneric hybrids of wheat (Lange and Wojciechowska 1976). These
factors are known to be implicated in the crossabilities of wheat
with H. bulbosum (Snape et al 1979) and with barley (Fedak and
Jui 1982). Similar crossability genes are reported in barley (Elbern
1981).
In wheat-rye crosses, the growth of the pollen tubes in the poorly
crossable types of wheat was found to be either slower (Singh and
Khanna 1988) or not retarded at all (Tozu 1966). Furthermore, pollen
tube inflation and bursting has also been shown to occur in
incompatible hybridizations between wheat and rye (Tozu 1966, Zeven
and Heemert 1970, Jalani and Moss 1980, Singh and Khanna 1988), and
barley and wheat (Fedak and Jui 1982). Similarly, growth of pollen
tubes were inhibited before penetration into embryo-sacs of
non-crossable wheats pollinated with H. bulbosum (Snape et al
1980).
Present paper deals with pollen germination and pollen tube behaviour
with the aim to determine the factors which reduce crossability in
the reciprocal crosses between wheat and barley. The effect of
hormones on crossability is also reported.
Materials and Methods
One variety of common wheat, Triticum aestivum, UP 2121,
one variety of durum wheat, T. durum, PBW 34 and two varieties
of diploid huskless barley, Hordeum vulgare, Karan 4 and Karan
265 were used in the present study.
The seeds of the varieties were sown in the field on 25th of Nov. and
2nd of Dec., 1989. The crosses were made reciprocally in all possible
combinations in February and March, 1990.
The styles along with the stigmas were detached from the top of the
pollinated flowers with forceps with the intervals of 5min, 30min,
60min, 4h and 24h after pollination. They were kept in 1:2
lacto-alcohol solution for 48h. Five styles were chosen at random
from each spike and all the pollen grains on the stigma were observed
for pollen germination. For pollen tube growth, the lengths of the
three longest pollen tubes in each style were recorded. These pistils
were washed in distilled water and stained with cotton blue solution
(D'Souza 1972). The pollen grains and the pollen tubes were stained
deep blue whereas the stylar tissue was either colorless or very
lightly stained. The data on pollen germination, pollen tube growth
and abnormal pollen tubes were taken from spikes without treatment of
hormones.
In order to clarify the effect of hormones on crossability between
wheat and barley, each of three growth hormones namely, Gibberellic
acid (GA3), Indole acetic acid (IAA), and Kinetin (KIN)
were sprayed on the floweres with the concentration of 75ppm,
respectively, after 24h of pollination.
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