| dc.description.abstract | The Inheritance of yield, fibre length and
airlines in Upland cotton (Gossypium hirsutum L.)
w s studied using Pi. P2r F1' F2, B1' 82 populations
in five Inter varietal crosses. The commercial
variety., UKAS9/240. (Pi) was a common parent In 11
the five crosses involving th early maturing
varieties. i.e., PRS 74, SR 1054-2, K 3400-7,
K 4371. K 4614. The six population were grown In
randomised blocks experiment with four replications
t the Cotton Research Station, Kibos. The six
characters studied were seed cotton yield, lint
yield, lint percentage, lint index, fibre length and
days to first poll opening_ For these characters,
the means,variances and standard errors were
calculated, and the estimates of these parameters
were in turn used in subsequent genetic analyses.
Scaling test was used to determine the presence of
additive, dominance and epistatic gene effects.
The gene effects were then estimated by Gamble·s
(1962) six parameter model. using gen ration means.
The six parameters represented the mean effects (!9.),
additive (~) and dominance (~) gene effects, and
the three types of dlgenic epistatic effects, (a ),
(-ad) nd (-dd). Heritability in narrow sense w estim ted using additive and phenotypic variances.
The magnitude s nd significance of the gen effects
were examined and compared in order to estimate
their relative import nee in the inheritance of
the characters. Significance of the gene effects
was tested by test. The means were used In
estimating het roses and inbreeding depression,
nd potence ratio. Correlations and regressions
( 11 )
among th.:lvarious characters were calculated from
the observations on single plants of F2 populations.
1~e results indicated that additive gene effects
were present in all the characters studied, and their
contribution to genetic variance was :important. Dominance
gene effects were also important in seed cotton yield,
lint p~rcentage, fibre length and days to first boll
opening, but were unimportant in lint index where additive
gene effects were predominant. Both additive x additive
epistasis and dominance x dominance epistasis appeared
to be less important than additive x dominance epistasis,
which made more contribution to the inheritance of seed
cotton yield, lint yield, lint percentage- Dominance x
dominance gene effects were more important for fibre
length and earlinesso
Heterosis for Beed cotton yield and lint yield
over mid-parent was not importanto Heterosis over
better parent was negative in all characters, therefore,
unimportant. Inbreeding depression occured
in all characters and in all crosses.
The highest positive correlation coefficients
were recorded between seed cotton yield and lint
yield (0.987·· to 0.996··)0 Days to first boll
opening did not show significant correlation with
other characters in most crosses, and the correlation
coefficients were often negative. All the yield
components and fibre length showed significant positive
correlation with each othero High correlation
coefficients also occurred between lint percentage and
lint index (0.230·· to 0.687··)0 Correlation coefficients
between othQr characters varied and were generally lower than
( 111)
rho se between he yield components Seed cotton
y eld howed high coefficients of determination
for lint yield, while lint index showed fairly
hi9h coefficient ts f determination for lint
percent ge.
Hybridi atlon and selection 1n the present
cross would be useful in d velo i;:'1v9 rleties
with improved characters su h s earliness, hi9h
yield of seed cotton and long fibr. ecurrent
selection and mass selection wo 1 be effective
in Improving cotton populations. It appeared
t~at lint percentage and lint index could be
more easily improved by selectin9 transgressive
segregates in the F2 populations then seed cotton
yield could be. | en |
