GENETIC ARCHITECTURE OF GRAIN YIELD AND ITS COMPONENTS IN BREAD WHEAT (Triticum aestivum L.) UNDER DIFFERENT DATES OF SOWING
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2013-06
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Abstract
The present investigation entitled “genetic architecture of grain yield and its
components in bread wheat (Triticum aestivum L.) under different dates of sowing”
was carried out with a view to estimate heterosis, combining ability and gene
action, genotype x environment interaction and stability parameters for grain yield
and its component traits along with biochemical parameters in bread wheat. The
experimental materials comprised of ten parents (LOK 1, GW 366, GW 173, HD
2932, DL 788-2, WH 1059, K 9906, KRL 213, RAJ 3765 and WR 885), their fortyfive
F1 hybrids and one standard check variety GW 496. This material was
evaluated in three different environments( three dates of sowing) in randomized
block design with three replications during rabi 2011-12 at Wheat Research
Station, Junagadh Agricultural University, Junagadh. The observations on five
randomly selected plants were recorded for 15 characters viz., days to heading, days
to maturity, plant height (cm), number of effective tillers per plant, length of main
spike (cm), number of spikelets per main spike, peduncle length of main spike
(cm), number of grains per main spike, 1000-grain weight (g), grain yield per plant
(g), biological yield per plant (g), harvest index (%) and biochemical parameters
like protein content (%), wet gluten content (%) and water absorption (ml). The
data were analyzed for heterosis and combining ability (Method-II, model-I of
Griffing, 1956a). The genetic components of variation were estimated according to
Hayman (1954) while, G x E interaction and stability parameters were calculated
following the model of Eberhart and Russell (1966).
The mean squares due to parents and hybrids (F1s) exhibited highly
significant differences among themselves for grain yield per plant and all its
component traits in all the three environments which indicated the existence of
considerable amount of genetic variability amongst parents and hybrids for all the
traits under study. Similarly mean squares due to parents vs. hybrids were found to
be significant for all the traits under all the three environments except days to
heading, number of grains per main spike and water absorption in E1, length of
main spike in E2 and plant height, peduncle length of main spike, number of grains
per main spike and harvest index in E3 indicating that the performance of parents
was different from that of crosses thereby suggesting the presence of mean
heterosis for all these characters. No specific consistency was observed with regard
to heterosis for grain yield and yield components in different crosses. This may be
due to interacting effects of different component traits in manifestation of heterosis
for grain yield. This reflected that in different crosses, path-way for releasing
heterotic effects varied from cross to cross.
Eleven hybrids over better parent and 17 hybrids over standard check variety
(GW496) exhibited significant and positive heterosis. The crosses K 9906 X
WR 885, K 9906 X RAJ 3765, GW 173 X WH 1059, GW 366 X GW 173, GW 366
X K 9906, HD 2932 X RAJ 3765, GW 366 X HD 2932, GW 366 X RAJ 3765, GW
173 X DL 788-2 and WH 1059 X RAJ 3765 manifested significant and desirable
standard heterosis for grain yield per plant and important yield components
therefore, such crosses could be exploited further for yield advancement in bread
wheat.
The general as well as specific combining ability variances were found to be
significant for all the traits evaluated in individual environment as well as pooled
over environments indicating the role of both fixable and non-fixable variances in
the expression of all the traits studied. However, the potence ratio (σ2 GCA/ σ2
SCA < 1) less than unity revealed the preponderance of non-additive gene action
for all the traits studied.
The parents GW 366, K 9906, WR 885 and HD 2932 were found to be good
general combiners for grain yield per plant. LOK 1, GW 173, HD 2932, DL 788-
2 and RAJ 3765 were emerged as good general combiners for early maturity. The
parents Dl 788-2, K 9906 and WR 885 for protein content; LOK 1, DL 788-2 and
WR 885 for wet gluten content and GW 173, HD 2932, WH 1059 and WR 885 for
water absorption were observed to good general combiners.
The estimates of SCA effects revealed that none of the top ten crosses for
SCA with respect to grain yield per plant was simultaneously superior for all the
traits. The cross K9906 x WR 885 with highest grain yield per plant had high SCA
effect for grain yield per plant, which involved good x good general combiners.
Other two superior cross combinations, (GW 366 x GW 173 and K 9906 x RAJ
3765) with respect grain yield per plant involved good x average combining
parents. The cross combinations involving good x poor or average x poor general
combiners besides exhibiting favourable additive effect of good or average
combining parents, manifest complementary interaction effect and thus result in
higher SCA effects. In the present study, such combinations for grain yield per
plant were GW 173 X DL 788-2, LOK 1 X RAJ 3765, LOK 1 X GW 173, DL 788-
2 X WR 885 and DL 788-2 X RAJ 3765.
The relative magnitude of additive components (D) was higher than both/
either of dominance components (H1, H2) for days to heading, days to maturity,
plant height, number of spikelets per main spike and number of grains per main
spike suggesting predominance of additive genetic variance for these characters.
For rest of the characters, magnitude of dominance components (H1, H2) was higher
than additive component (D). The average degree of dominance (H1/D)1/2 indicated
over dominance for all the traits evaluated except days to maturity, plant height,
number of spikelets per main spike and number of grains per main spike. The
distribution of genes with positive and negative effects (H2/4H1) in the parents was
observed nearly symmetrical for all the traits except days to maturity and number
of spikelets per main spike. The value of h2/H2 was very low in case of days to
heading, plant height, number of spikelets per main spike, number of grains per
main spike, 1000 grain weight, protein content, wet gluten content and water
absorption indicating that number of gene groups which exhibited dominance could
not be estimated properly. The estimates of ratio h2/H2 for number of effective
tillers per plant, length of main spike, peduncle length of main spike, grain yield
per plant, biological yield per plant and harvest index suggested the involvement
few genes, normally one gene group for the control of inheritance. In general
narrow sense heritability was found to be less than 50 per cent for all the traits
indicating comparatively, more role of dominance gene effect in the expression of
grain yield and its attributes.
The stability analysis revealed the presence of significant genotype x
environment interactions (G x E) for days to maturity, number of spikelets per main
spike, number of grains per spike, grain yield per plant, biological yield per plant
and wet gluten content when tested against the pooled error. This suggested that
genotypes interacted significantly in different environments for these traits. Among
the parents, GW 366, WR 885 and HD 2932 were found to be stable for high yield.
Sixteen hybrids recorded high mean grain yield with unit regression and
non-significant deviation from regression among which top five stable hybrids were
K9906 X RAJ 3765, GW 173 X WH 1059, HD 2932 X RAJ 3765, WH 1059 X
KRL 213 and LOK 1 X RAJ 3765. The hybrids GW 366 X K 9906 and K 9906
X WR 885 found to be stable for grain yield per plant under better environmental
condition.
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Keywords
BREAD WHEAT