GENETICS OF SEED COTTON YIELD AND ITS COMPONENT TRAITS IN COTTON (Gossypium hirsutum L.)
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2015-02
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Abstract
Key words: Cotton (Gossypium hirsutum L.), Generation mean analysis,
Trigenic ten parameter model, Heterosis, Inbreeding depression.
The present investigation was undertaken with a view to generate genetic
information on gene effects, heterosis and inbreeding depression for seed cotton yield
and its component traits. The experimental materials consisted of twelve generations,
namely P1, P2, F1, F2, B1, B2, B11, B12, B21, B22, B1s and B2s of four crosses of cotton
viz., Deviraj x GBHV-170, G.Cot-10 x MR-786, G.Cot-12 x GTHV-95/145 and
76IH20 x GJHV-460. Experiment was laid-out in Compact Family Block Design with
three replications during Kharif 2013 at Cotton Research Station, Junagadh
Agricultural University, Junagadh. The observations were recorded on twelve
characters on five randomly selected plants in each replication for P1, P2 and F1; ten
plants for B1 and B2 and twenty plants for each of F2, B11, B12, B21, B22, B1s and B2s.
The analysis of variance between families revealed that the mean square due
to crosses were significant for all the characters except boll weight, ginning
percentage, seed index and oil content. Among the progenies within each family, the
analysis of variance indicated significant differences among the generation means for
all the traits studied in all the four crosses.
Mean performance of F1 hybrids were higher than their respective better
parents for days to flowering, days to 50 % boll bursting, number of bolls per plant,
seed cotton yield per plant, seed index and oil content in all the four crosses; for
number of monopodia per plant in Deviraj x GBHV-170 and G.Cot-12 x
GTHV-95/145; for number of sympodia per plant and lint index in G.Cot-10 x MR-
786 and G.Cot-12 x GTHV-95/145; for boll weight in crosses, Deviraj x GBHV-170,
G.Cot-10 x MR-786 and G.Cot-12 x GTHV-95/145 and for ginning percentage in
crosses G.Cot-12 x GTHV-95/145 and 76IH20 x GJHV-460. Moderate inbreeding
depression was noticed for seed cotton yield and some of its component traits in four
crosses of cotton. Mean performance of all the double backcrosses were higher than
their respective better parents in cross G.Cot-10 x MR-786 for number of monopodia
per plant and oil content; in cross G.Cot-12 x GTHV-95/145 for ginning percentage,
lint index and oil content and in cross 76IH20 x GJHV-460 for seed index and lint
index.
Significance of simple scaling tests and Cavali’s joint scaling test indicated
that the presence of gene interactions for all the traits in all four crosses. In sixparameter
model by weighted least square technique, the components 'm' and digenic
[j] were found significant for seed index in cross Deviraj x GBHV-170 and 'm', [d],
[h] and all the digenic ([i], [l] and [l]) were significant for oil content in 76IH20 x
GJHV-460 along with non-significant of 2
(2) value at six degrees of freedom in both
cases showing the adequacy of digenic six-parameter model in both the traits.
The crosses and the traits which were found significant for 2
(2) were
subjected to trigenic ten-parameter model. The trigenic ten-parameter model was
found to be adequate in cross Deviraj x GBHV-170 for number of monopodia per
plant; in cross G.Cot-10 x MR-786 for seed cotton yield per plant, days to 50 % boll
bursting, number of bolls per plant, boll weight, seed index, lint index and oil content;
in cross G.Cot-12 x GTHV-95/145 for number of monopodia per plant, ginning
percentage, seed index and lint index and in cross 76IH20 x GJHV-460 for number of
monopodia per plant, seed index and lint index indicating major role of trigenic
interaction for the inheritance of above said traits. On the other hand, 2 (3) with two
degrees of freedom was significant for remaining traits in different crosses showing
the presence of higher order epistasis and/or linkage. All the ten-parameters were
significant only for seed cotton yield per plant and number of monopodia per plant in
cross G.Cot-12 x GTHV-95/145.
The observed and expected estimates for heterosis over mid parent, over better
parent and inbreeding depression were in close agreement with each other in all the
four crosses for all the traits except for plant height in Deviraj x GBHV-170 and
G.Cot-10 x MR-786 and days to 50 % boll bursting in G.Cot-12 x GTHV-95/145 for
both heterosis over mid parent and inbreeding depression; number of monopodia per
plant in cross G.Cot-10 x MR-786 only for heterosis over mid parent as well as
number of bolls per plant and ginning percentage in Deviraj x GBHV-170, plant
height in G.Cot-12 x GTHV-95/145 and days to flowering in 76IH20 x GJHV-460
only for inbreeding depression.
Overall from the present study, it could be concluded that seed cotton yield per
plant and its component traits recorded in four cotton crosses were governed by
additive, dominance and digenic and/or trigenic epistasis gene effects. Biparental
mating could be followed which would facilitate exploitation of both additive and
non-additive gene effects simultaneously for genetic improvement in cotton.
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Keywords
cotton