(go to
KOMUGI Home) (go
to WIS List) (go to NO.87
Contents)
Materials and methods
Initially, six cultivars (WC 29, WH 291, SGP 14, RAJ. 1972, WH
377 and HD 2329) of spring wheat were crossed in all possible
combinations, excluding reciprocals, and their 15
F1's were
grown in a Randomized Block Design with three replications. Five
plants in each replication were selected for recording observations.
Six basic generations
(P1, P2, F1, F2,
BC1, BC2) of three crosses viz, WC 29 x WH 291,
SGP 14 x RAJ. 1972 and WH 377 x HD 2329 selected on the basis of
combining ability were developed to determine gene effects and to
predict the frequencies of transgressive segregants. The six basic
generations were grown in a Randomized Block Design with three
replications. Five plants in each non-segregating generation, 25 in
each backcross generation and 50 plants in each F2
population were taken for recording observations. To predict
frequency of transgressive segregants using F3 family
data, a random sample of 30 F2 plants was taken to produce
30 F3 families of each cross. The parents and progenies
were grown in an Augmented Design with six blocks. Fifteen plants in
each F3 families of each cross and five plants in each of
the parents in each block were taken at random for recording
observations.
To identify transgressive segregants in the F2 population,
the parents, F1's and F2 population of each
cross were grown in a Randomized Block Design with three
replications. Five plants in each of the non-segregating generations
and 350 plants in each of the F2 population in each
replication were selected randomly for recording observations. The
F3 progeny of selected transgressive segregants were grown
for progeny testing.
To identify transgressive segregants in biparental progenies (BIPs)
and F4 bulks, the parents, BIPs and F4 of each
cross were grown in an Augmented Design with six blocks. Five plants
of each parent in each block and 450 plants in each population of
each cross were taken at random to identify transgressive
segregants.
In each experiment, the row length was 6m, spaced 25 cm apart. The
plant to plant distance within rows was 15 cm. To ensure leaf rust
development, spreader rows were planted around each replication in
each experiment. Spreader rows were inoculated artificially with a
mixture of races of leaf rust of wheat. The observation on leaf rust
was recorded following Loegering (1959). Field resistance expressed
as a coefficient of infection was computed as described by Yadav
(1984).
Analysis of variance for Randomized Block Design and Augmented Design
was done following Addelman (1969) and Federer (1961), respectively.
Combining ability analysis was carried out following Method 4, Model
1 of Griffing (1956). Initially, generation mean analysis following
three parameter model as suggested by Cavalli (1952) was carried out.
A six parameter model suggested by Hayman (1958) was applied if the
three parameter model was found to be inadequate. The
frequency of transgressive segregants was predicted from generation
mean analysis and F3
family alone following Jinks and Pooni (1976, 1980).
<--Back | -->Next
(go to
KOMUGI Home) (go
to WIS List) (go to NO.87
Contents)