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Significant general combining ability (gca) and specific combining ability (sca) x
environment interactions were observed for most of the characters. The best general combiners in
all the environments were: C-2602-WIR-6109 for monopodia per plant and seed cotton
yield, LH 1861 for bolls per plant and RS 2115 for seeds per boll. Crosses exhibiting highest
sca effects coupled with high per se performance were LH 1836 x H 1123 for plant
height, bolls per plant, seed index and seed cotton yield; and PIL 8-5 x RS 2115 for plant
height and seeds per boll.
Hybridization is the most potent technique for breaking yield barriers and
evolving varieties having a built-in high yield potential. The selection of suitable parents
for hybridization is one of the most important steps in a hybridization program.
Selection of parents on the basis of phenotypic performance alone is not a sound procedure
since phenotypically superior lines may yield poor recombinants in the segregating
generations. It is, therefore, essential that parents should be chosen on the basis of their
genetic value. The use of parents of known superior genetical worth increases probability
of success. There are several techniques for the evaluation of genetic makeup of
varieties or strains. Out of these, diallel cross analysis is in common use. The combining
ability analysis helps the breeder in selection of suitable parents for the breeding program
and provides information regarding the cross combination to be exploited commercially.
It also furnishes the information on additive and non-additive portions of genetic
variance present in the material under study. As environment plays an important role in
the expression of a character and greatly influences the combining ability estimates,
the study in a single environment may not provide reliable information. The
present experiment was, therefore, conducted to get the information on combining ability
and the nature of gene action involved in the inheritance of seed cotton yield and
other component characters in upland cotton under different environments.
Ten genetically diverse lines of G.
hirsutum L. namely, F 1867, F 1861,
C-2602-WIR-6109, PIL 8-5, LH 1836, LH 1861, LH 1896, Pusa 101, H 1123 and RS 2115 were crossed
manually in all possible combinations in half diallel fashion at Agricultural Research
Station, Sriganganagar, during Kharif 2001. All 10 parents and their 45 F1's were raised in
a randomized block design replicated thrice in three environments (E1, E2 and E3)
at Agricultural Research Station, Sriganganagar, during Kharif 2002. The environments were created by applying three sowing dates, i.e., early sowing on May 11(E1), timely
sowing May 26 (E2) and late sowing on June 10, 2002 (E3). The temperature during the week
of sowing ranged from 27.80-46.01 oC for E1; 26.30-44.17 oC for E2; and 29.71-44.37 oC
for E3. Each entry was represented by two rows with inter-row and intra-row spacing
of 67.5 cm and 60 cm, respectively. The data were recorded on 10 competitive
randomly selected plants per replication for plant height (cm), number of sympodia per
plant, number of monopodia per plant, number of bolls per plant, number of seeds per
boll, ginning percentage (%), seed index (g), lint index (g), 2.5% span length (mm), fiber
fineness (micronaire value) and seed cotton yield per plant (g) while only one character, i.e.,
days to 50% flowering was recorded on plot basis. The mean values over replications of all
the characters were subjected to analysis following Griffing (1956) as extended by
Singh (1973) using model-1, method-2.
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