EVALUATION OF BREAD WHEAT (Triticum aestivum L.) GENOTYPES FOR GRAIN YIELD, ITS COMPONENTS AND TERMINAL HEAT TOLERANCE 2919
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Date
2019-08
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JAU, JUNAGADH
Abstract
An experiment was conducted to assess the genetic variability, genetic
divergence, correlation coefficients, path analysis and heat tolerance for grain yield and
its attributes using a set of 48 genotypes of bread wheat (Triticum aestivum L.) at
Wheat Research Station, Junagadh Agricultural University, Junagadh during Rabi
2017-2018 in randomized block design with three replication under timely (D1) and late
(D2) sowing conditions. The characters studied were days to 50% flowering, days to
maturity, grain filling period, plant height, number of effective tillers per plant, length
of main spike, number of grains per main spike, grain weight per main spike, grain
yield per plant, biological yield per plant, harvest index, 1000 grain weight, chlorophyll
content (CHLa & CHL21), canopy temperature depression (CTDvg & CTDgf) and heat
susceptibility index.
The analysis of variance revealed the presence of sufficient variability under D1
& D2 conditions among the genotypes studied. The values of phenotypic coefficient of
variation in both sowing conditions were slightly higher than that of genotypic
coefficient of variation for all the traits studied, indicating that the apparent variation is
not only due to genotypes but also due to the influence of environment on the
expression of characters studied. High values of GCV were observed under timely
sowing condition (D1) for canopy temperature depression at grain filling stage, while
under late sowing condition (D2) for canopy temperature depression at grain filling
stage followed by canopy temperature depression at vegetative stage.
The genetic divergence assessed by Mahalanobis D
2
analysis showed wider
genetic diversity among 48 genotypes which were grouped in to 11 and 9 clusters under
timely and late sowing conditions, respectively. The clustering pattern did not show
any relationship between geographic distributions. Under timely sowing condition, the
maximum inter-cluster distance was found between clusters IV (DWAP 1530) and VI
(PHSL 5). In case of late sowing condition, the maximum inter-cluster distance was
found between clusters VII (GW 498) and IX (VL 1003). For timely sowing condition,
the attributes, viz., days to 50 % flowering, chlorophyll content, CTD and days to
maturity, while for late sowing condition, the characters, chlorophyll content, CTD and plant height found useful for selection of parents in hybridization programme as these
traits contributed maximum towards total genetic divergence.
High heritability coupled with high genetic advance expressed as percentage of
mean were observed for all characters except under D1 condition for plant height,
harvest index, 1000-grain weight and chlorophyll content at vegetative stage, while
under D2 condition for days to maturity, plant height, length of main spike, biological
yield and harvest index which may be attributed to the preponderance of additive gene
action and possessed high selective value and thus, selection pressure could profitably
be applied on these characters for their rationale improvement.
Under timely sowing condition, grain yield per plant exhibited highly
significant and positive genotypic and phenotypic correlation with biological yield per
plant and significant and positive correlations at both levels with harvest index. Under
late sowing condition, grain yield per plant had highly significant and positive
genotypic and phenotypic correlation with harvest index and biological yield per plant.
Chlorophyll content at anthesis was significantly but negatively correlation with grain
yield per plant at both levels.
The path coefficient analysis revealed that the biological yield per plant, harvest
index, days to 50% flowering and grain filling period showed high and positive direct
effect on grain yield per plant under timely sowing condition. While, in case of late
sowing condition, path coefficient analysis revealed that, biological yield per plant,
harvest index and days to 50% flowering exhibited high and positive direct effect on
grain yield per plant.
On the basis of heat susceptibility index (HSI), the genotypes CG 1014, HI 1544
and WH 730 while on the basis of canopy temperature depression the genotypes
AKAW 4842 under timely sown and UP 2959 under late sowing condition found
promising for heat tolerance with respect to grain yield per plant and hence these
genotypes should be utilized in future wheat breeding programme for heat tolerance.
The final conclusion that can be reached from variability, divergence,
correlations, path coefficient analysis and heat tolerance is that under timely sowing
condition (D1), biological yield per plant, harvest index, canopy temperature
depression at grain filling stage, days to 50% flowering and grain filling period, while
under late sowing condition (D2), biological yield per plant, harvest index, canopy
temperature depression at anthesis and days to 50% flowering found to be the most
important component characters. Hence, these traits should be considered as selection
criteria for yield improvement in wheat for the material studied. The genotypes viz.,
DWAP 1530, PHSL 5, GW 498, VL 1003, CG 1014, HI 1544, WH 730, AKAW 4842
and UP 2959 were found promising for utilizing in further breeding programme.