Performance of F1 and F2 Hybrids of Cotton (Ggossypium hirsutum L.) for Yield and Yield Components
The objective of this study was to evaluate the potential of F2 hybrids by comparing them with parents, commercial varieties and F1, s for yield, yield components and fibre quality. The genetic design was half diallel, consisting of five parents and additional five direct crosses were attempted to study inbreeding depression (CIM-496, MNH-554, FH-901, FH-945, LRA-5166, 10 F1 and 10 F2). The difference among genotypes were determined. The highest yielding parent was CIM-496 with 3521 kg ha-1 followed by MNH-554 with 3268 kg ha-1. While the variety FH-901 with 2391 kg ha-1 showed minimum yield among the parents. The cross combinations MNH-786 x VH-144, MNH-554 x LRA-5166 and CIM-499 x LRA-5166 showed minimum inbreeding depression i.e., -39.72, -27.85 and -22.72 for seed cotton yield, yield components and fibre traits than expected inbreeding depression i.e., 50.0%. General combining ability mean squares were significant for all traits and specific combing ability mean squares were also significant for all traits. The GCA effects were higher than SCA effects for all traits, which indicates that additive gene action is prevailing with dominant gene action for expression of these traits. The variety FH-901 was the best general combiner for the yield and yield components. It is concluded that F2 can be used for availing the heterosis after evaluating the proper cross combinations, be reduced.
Cotton is a nearly self pollinated crop (less than 1% cross pollination) in
our environment due to indiscriminate use of insecticides. The improvement in
its plant type can be brought through hybridization. It brings together certain
superior genes from different promising cotton strains. Combining ability is
a tool to predict combining potentials of different strains for various traits
and to select the best from them. Using heterosis to increase yield of cotton
has been objective of breeders, but no use in world except in countries where
a vast labour force was available to make emasculation and crosses by hand,
(Chaudhry, 1977b). In India at least 40% of cotton production is from intra-specific
hybrid of G. hirsutum and 8% of its production is from G. hirsutum
x G. barbadense hybrids (Chaudhry, 1977b). The yield increase of
hybrid over the better parents or best commercial varieties due to sufficient
magnitude of heterosis. Meredith (1998) using recent data showed heterosis of
21.4% for F1 hybrid and 10.7% for F2 but heterosis of
fibre properties was small averaging from 0-2% and concluded that both F1
and F2 hybrids can produce significantly higher yields than the best
yielding parents or the commercial cultivars. In Pakistan the hybrid of NIAB
Karishma x CIM-435 was given to the growers for testing in the field which showed
10.5 increase in seed cotton yield over the best parent and best commercial
variety as NAIB Karishma was the best variety during 1999-2000 (Anonymous, 2000).
The magnitude of heterosis has been documented by Loden and Richmond (1951),
Davis (1978), Meredith (1984), Baru (1995), Meyer (1975), Sheetz and Quisenberry
(1986) and Iqbal et al. (2003). Breeding research needs to address all
possibilities to increase yield, including the use of heterosis. The average
cotton yield for Pakistan and world has showed no increase since 1992 (Chaudhry,
1977a). The major limiting factor to use heterosis in cotton is the lack of
an efficient, dependable crossing system. The discovery of male sterile cytoplasm
(Olvery, 1986) and restorer factor Weaver and Weaver (1977) give encouragement
to breeders that hybrids in cotton are obtainable. However the complexities
of developing good combiner with dependable fertility restoration percent are
major problems for hybrid production. To avoid inconsistency of results from
male sterile and restorer factor and cost of producing F1 seed, the
commercial use of F2 hybrids has been proposed by Olvery (1986) and
Iqbal et al. (2003). One method circumventing this inconsistence is to
use male gametocytes (Sheetz and Quisenberry, 1986). However, due to lack of
dependable and economic method of controlling the insect pattern carrier, it
still has not been practical to produce F1 hybrids. The several well
designed studies showed the potential for using F2 hybrids. Tang
et al. (1993) evaluated yield performance of 64 F2 s
from four environment and reported 11.8% higher yields than that of commercial
verities. Weaver (1984) reported 13.2 and 7.1% heterosis over mid parents for
F1 and F2, respectively. The advantage of use F2,
s is that it might have a broad range of adaptation than commercial varieties
due to genetic variations. Reid (1995) reported that F2 superiority
over their best parents was only detected under stress conditions. Baure and
Gereen (1996) also reported F2, s greater superiority over their
best parents was in lower yielding sites. Iqbal et al. (2003) revealed
that F2 generation can also be cultivated in field for use of heterotic
vigor and cost of seed production can be decreased. The objective of this study
was to compare the yield and fibre properties of F1, F2
and combining ability of the genotypes.
MATERIALS AND METHODS
A half diallel genetic design consisting of five parents, 10 F1 and 10 F2 hybrids grown in three replications at Cotton Research Station, Multan during 2003-2004. In addition to ten F2 hybrids of diallel, five promising direct crosses were also included for testing inbreeding depression. The F1 seeds were produced by hand crosses, F2 seeds were produced by selfing the hybrids 2004-2005. The parents were CIM-496, MNH-554, LRA- 5166, FH-901 and FH-945. The experimental design was Randomized Complete Block Design with three replications. Standard cultural methods for Multan region were used. The parents and F1 were grown in four rows plot of 30ft long, while each genotypes of F2 was grown in ten rows plot of 30ft long. Ten single guarded plant samples were hand harvested from each replication of F1 and parent, while 50 guarded plants were hand harvested from each replication of F2. These samples were used to determine the boll weight, lint % and fibre quality traits. The seed cotton yield ha-1 was determined from the total plot weight while combining ability (both general combining ability and specific combining ability) analysis were made using the method given by Griffing (1956) (method-2, model-2).
RESULTS AND DISCUSSION
The objective of this study was to compare consistency of performance of F1
and F2 generations. Mean yield, yield components and fibre properties
for five parents, are given in Table 1, which showed wide
genetic differences for all characters under study among parents. The yield
superiority of F1 hybrid over F2 and their parents is
presented in (Table 2). Usually the heterosis denoted mid
parent value H but the major interest in present study was the yield comparison
of F2 hybrid with F1 and established variety i.e., CIM-496, which
covered about 40% area in Punjab (Anonymous, 2005, 2006). The highest yielding
varieties CIM496 averaged 3521 kg ha-1. The increase and decrease
percentage in yield of F2 hybrid over F1 and standard
varieties is given in Table 2, from which it is evident that
several F2 hybrids were superior in yield to well established variety
CIM-496. The highest yielding F2 hybrid MNH - 786xVH-144, CEDIXxCIM-499
and LRA-5166xCIM-499 yielded seed cotton 6013.6, 5864 and 5857.3 kg ha-1,
respectively. Assuming that dominant gene action causes the Heterosis, the F2
yield is expected to loss 50% of the heterosis expressed by F1.
The maximum hybrid vigor loss for yield was observed -42.12% in cross MNH-554xLRA-5166
followed by CIM-499xLRA-5166 and CIDEXxCIM-446 showed -39.7 and -27.85% loss
of heterosis for yield, respectively. While the minimum hybrid vigor loss for
yield was recorded -3.04 and -5.54% for CIDEXxCIM-499 and MNH-554xFH-945, respectively.
The highest yielding F2 hybrids MNH-786xVH-144, CEDIXxCIM-499 and
LRA-5166xCIM-499 loose -12.03, -42.12 and -39.72% hybrid vigor over F1
but the yield was quite higher than the best commercial variety CIM-496.
The increase in yield of these three F2 hybrid was 34.41, 15.41 and
14.65% over CIM-496, respectively. The inbreeding depression of highest yielding
F1 hybrids was about what was expected on a 50% decrease in dominance
from F1 to F2. Several crosses however shown little inbreeding
depression in Table 2. Meyer (1975), Sheetz and Quinseberry
(1986) and Iqbal et al. (2003), have reported high yielding F2
hybrids that produced greater yield than expected on the basis of their F1
and parental performance. This deviation of F2 from expected could
be due to non-additive gene action other than dominance or plant competition
with in the plant population.
|| Mean square of various plant characters of cotton of 5x5
|*Significant, **Highly significant
The results of present studies showed, for total yield and yield components
of F2 hybrids could be competitive with established commercial variety.
The percent increase for yield components and fibre quality traits over best
commercial variety of F1 and F2 population is presented
in Table 2. These above mentioned crosses showed heterosis
for almost all traits under consideration from commercial variety except for
GOT (%) and staple length. Meredith (1984) summary of 18 states research experiment
on heterosis in cotton reported on an average total yield heterosis of 18.5%.
The hybrid vigor loss in F2, for cross CEDIX x CIM-499 and MNH-554
x FH-945 was -3.04 and - 5.54 for seed cotton yield, respectively. The hybrid
MNH786 x VH144 showed highest yield loosed hybrid vigor - 6.25, -3.05, -12.03,
-2.16, -2.13 %, for boll weight, boll no, seed cotton yield, GOT and staple
length, respectively (Table 2). The hybrid vigor loss for
LRA-5166 x FH-901 was -2.94, -8.41, -12.92, -8.39 and -1.41 for boll weight,
No. of boll, yield , G.O.T. and staple length respectively (Table
2). Similarly inbreeding depression for MNH-554 x LRA-5166 was - 8.17, -1.77,
-42.12, -6.36 and -3.33% for boll weight., boll no, seed cotton yield, GOT and
staple length, respectively (Table 2). These results indicated
that inbreeding depression for these crosses is less than 50% for all traits
under study. It is also concluded from these results that F2 generation
can also be cultivated in field for the use of heterotic vigor and cost of seed
production can be decreased. The results are also in according to the previous
findings of Meyer (1975), Sheetz and Quinseberry (1986) and Iqbal et al.
(2003). The significant deviation of F2 in hybrid vigor (Inbreeding
depression) from expected 50% could be due to non additive gene action other
than dominance. From these results it can also be concluded that F2, s
can produce better combination of yield and fibre quality e.g., CIM-499 x LRA-5166,
LRA-5166 x FH-901. On the basis of genetic variation within F2, it
might have broader range of adaptation than conventional varieties and F1.
So the question concerning the stability across environments of parents, F1,
F2 remains open as it will require a greater range of climate, soils,
pest management and environments to determine while F2 hybrids are
more adoptable than their parents in F1 hybrids. In general the inter
actions of yield components with environments were of lesser magnitude than
for total yield. From Table 3 and 4 it is
evident that GCA variances were significant for all the traits and SCA variances
were also significant at p = 0.05%. The variety FH-945 is the best general combiner
for No. of bolls per plant, boll weight, seed cotton yield, GOT and staple length
and similarly FH-901 is good general combiner for earliness (NFB), but MNH-554
is also good combiner for GOT (Table 5). The cross combinations
MNH- 554 x LRA- 5166, LRA-5166 x CIM-499, are valuable crosses for seed cotton
yield and its components as these crosses had high SCA effect for seed cotton
yield and its components (Table 6). These results suggested
that at least one parent should be well adopted for developing hybrid having
high yield. The crosses MNH-554 xFH- 901, CIM- 499 xFH- 901 and LRA- 5166 x
FH- 901 showed low inbreeding depression had also low specific combining ability
for all traits under study (Table 2 and 6).
As SCA effect are due to dominant gene action, if dominant gene action will
be present the expected inbreeding depression in F2 will be 50%.
As in these three crosses the value of SCA effect is low indicating that other
than dominant gene action is prevailing due to the reason, inbreeding depression
for these three crosses is less than 50%. As in these three crosses FH- 901,
which has the high GCA effect for seed cotton yield, NFB and boll weight.
|| Mean square of combining ability analysis in 5x5 diallel
crosses of cotton
|*Significant, **Highly significant
|| Estimation of general combining ability effects for yield,
yield components and fibre tester in a set of 5x5 diallel crosses among
five cotton varieties
|| Estimation of special combining effects for yield, yield
components and fiber tester in a set of 5x5 diallel crosses among five cotton
Table 5, indicating that FH-901 is a good general combiner for above mentioned
traits. For hybrid vigor choosing of second parent is bit more difficult. No
pattern of variety related for the selection for second parent was evident.
An expectation exists when fibre quality is major breeding objective, then one
must choose at least one parent that has above average fiber properties. The
genetic differences among the potential parents required high heterosis, it
is no assurance that diverse parents will produce high heterosis. It is not
essential that diverse parents should have high hybrid vigour than commercial
variety. Further research has to be conducted to identify the parents/hybrids
that show high hybrid vigour in F1 and maintained in F2
with low inbreeding depression for commercial utilization of F2 hybrids
to overcome the CLCV and other field problems.
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