HETEROSIS AND COMBINING ABILITY IN INTER-SPECIFIC COTTON HYBRIDS (G. hirsutum L. × G. barbadense L.)
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Date
2012
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ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY
Abstract
The study was carried out during kharif 2011-12 at Regional
Agricultural Research Station, Lam Farm, Guntur with 45 hybrids along with
their 14 parents (9 lines and 5 testers) to elicit information on genetic
variability, heritability, genetic advance, combining ability, heterosis,
correlation and the magnitude of direct and indirect effects.
The data were recorded on 16 economically important characters viz.,
days to 50% flowering, plant height (cm), number of monopodia plant-1,
number of sympodia plant-1, number of bolls plant-1, boll weight (g), seed index
(g), lint index (g), ginning out-turn (%), 2.5% span length (mm), micronaire
value (10-6 g/inch), bundle strength (g/tex), uniformity ratio, fibre elongation
(%), lint yield plant-1 (g) and seed cotton yield plant-1 (g).
The analysis of variance revealed significant differences among the
genotypes for all the characters studied indicating that the material used in the
present investigation possessed sufficient variability. The phenotypic
coefficients of variation were higher than the genotypic coefficients of
variation indicating the influence of the environment on the expression of the
traits. High variability coupled with moderate heritability and high genetic
advance as per cent of mean was observed for seed cotton yield plant-1 (g)
indicating the operation of both additive and non-additive gene action in the
inheritance of the trait.
The ratio of general combining ability components of variance to
specific combining ability components of variance indicated the preponderance
of additive gene action for days to 50% flowering, boll weight (g), 2.5% span
length (mm), micronaire (10-6g/inch), bundle strength (g/tex), uniformity
ratio and fibre elongation (%). While, the trait plant height (cm) was
influenced by both additive and non-additive gene action. Whereas, nonadditive
gene action is important for number of monopodia plant-1, number of
sympodia plant-1, number of bolls plant-1, seed index (g), lint index (g), ginning
out-turn (%), lint yield plant-1 (g) and seed cotton yield plant-1 (g).
Among the lines, L 761 was identified as good general combiner based
on gca effects and per se performance for the majority of the characters viz.,
plant height (cm), number of bolls per plant, boll weight (g), 2.5% span length
(mm), bundle strength (g/tex), fibre elongation (%), lint yield plant-1 (g) and
seed cotton yield plant-1 (g) and among the testers, TCB 26 found to be good
general combiner except for the characters viz., days to 50% flowering, plant
height (cm), number of monopodia plant-1, number of sympodia plant-1 and
micronaire value (10-6g/inch) based on gca effects and per se performance. The
crosses L 799 × TCB 26 and L 1203 × GSB 41 showed positive and
significant specific combining ability effects for seed cotton yield per plant
along with some of the fibre quality characteristics.
Significant positive heterosis over the mid parent, better parent and
check was observed for seed cotton yield and yield components in six crosses
viz., L 1203 × SUVIN, L 770 × GSB 41, L 799 × TCB 26, L 799 × SUVIN,
L761 × TCB 26 and L 763 × TCB 26.
The character association and path analysis studies revealed number of
bolls per plant, boll weight (g), 2.5% span length (mm) and lint yield plant-1 (g)
had significant association along with positive direct effects on seed cotton
yield plant-1 (g). The present study revealed that major emphasis should be
laid on selection process with lint yield plant-1 (g) via number of sympodia
per plant, boll number and boll weight (g) without sacrificing desirable fibre
quality by adopting restriction selection model.
Based on sca effects, per se performance and heterosis the crosses,
L 799 × TCB 26 and L 1203 × GSB 41 are found to be promising for seed
cotton yield. While, the cross L 765 × TCB 26 was found superior for fibre
quality traits with on par yield performance with check. These hybrids may be
exploited for commercial cultivation after thorough testing in different
environments for its superiority and stability. The progeny of these crosses may
be further studied to isolate superior segregants in further generations.
Description
Keywords
cotton, yields, planting, sowing, biological phenomena, genetics, heterosis, crossing over, additives, selection