GENETIC ANALYSIS OF GRAIN YIELD AND ITS COMPONENTS IN WHEAT (Triticum aestivum L.) UNDER DIVERSE ENVIRONMENTS
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Date
2011-01
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jau,junagadh
Abstract
Six generations, namely P1, P2, F1, F2, BC1 and BC2 of eight crosses of bread wheat viz., AKW 770 x MP 4010 ( cross 1) , AKAW 2862-1 x MACS 2496 (cross 2), CLN 1 x GW 273 (cross 3), CLN 5 x GW 322 (cross 4), GW 9715 x K 9102 (cross 5), NWL 1 x GW 496 (cross 6), P 11616 x PBW 524 (cross 7) and RWP 2002-2 x LOK 1 (cross 8) were grown under timely (E1) and late (E2) sowing conditions at Wheat Research Station, Junagadh Agricultural University, Junagadh to study the gene effects, heterosis, inbreeding depression, heritability, genetic advance and genetic correlation for grain yield and its components. Experiment was laid-out in Compact Family Block Design with three replications. The observations were recorded on five randomly selected plants from P1, P2 and F1, forty plants from F2 and twenty plants from BC1 and BC2 generations in each replication for thirteen characters viz., days to heading, days to maturity, plant height, number of effective tillers per plant, length of main spike, number of grains per spike, flag leaf area, grain filling period, peduncle length of main spike, grain yield per plant, 1000-grain weight, biological yield per plant and harvest index.
The analysis of variance between families revealed that the mean squares due to crosses were significant for all the characters under both the environments. The analysis of variance among progenies within each family indicated significant differences among six generation means for all the characters studied in all the crosses except plant height in cross 8, length of main spike in cross 1 and cross 5 and grain filling period in cross 1 and cross 4 under timely sown condition and length of main spike in cross 4 and cross 6, grain filling period in cross 1 and cross 6 and harvest index in cross 1, cross 3 and cross 6 under late sown condition. This indicates the sufficient variability in the material under study.
On the basis of individual scaling test A, B and C and joint scaling test, the additive-dominance model was found adequate for description of variation in generation means for number of effective tillers per plant in cross 6, number of grains per spike in cross 1 and cross 6, grain filling period in cross 7, grain yield per plant and biological yield per plant in crosses 3, 6 and 7 and harvest index in cross 6 and cross 7 under timely sown condition and days to maturity in cross 8, number of effective tillers per plant in cross 5, flag leaf area in cross 1 and cross 8 and biological yield per plant in cross 4 under late sown condition. For remaining cases, either all or the three or any of the individual scaling test A, B or C were found significant. The application of joint scaling test also expressed significant Chi-square values for these cases confirming the involvement of digenic interaction parameters in the inheritance of these characters.
On the basis of perfect fit solution of six parameter model, main effects m, (d), (h) and all the three digenic interactions (i), (j) and (l) were significant for days to heading in crosses 2, 3, 4 and 6, for days to maturity in crosses 2, 4, 5 and 8, for plant height in crosses 1, 2 and 4, for number of effective tillers per plant in cross 1, for length of main spike in crosses 2, 3 and 6, for number of grains per spike in crosses 2, 7 and 8, for flag leaf area in cross 2, for peduncle length of main spike in crosses 3, 4, 7 and 8, for grain yield per plant in cross 4 and for 1000-grain weight in crosses 3 and 6 under timely sowing. While under late sowing, these all the six parameters were significant for days to heading in crosses 1, 2, 4 and 8, days to maturity in crosses 4 and 7, for plant height in crosses 2, 3, 6, 7 and 8, for number of effective tillers per plant in crosses 1, 2 and 4, for number of grains per spike in crosses 1 and 4, for grain filling period in crosses 7 and 8, for peduncle length of main spike in crosses 4 and 5, for grain yield per plant in cross 5 and for 1000-grain weight in crosses 1 and 8. These indicated the involvement of additive, dominance as well as epistatic gene interaction for controlling the traits.
For the characters where evidence of digenic epistatic interaction was obtained under timely sowing, only additive (d) component was found significant for length of main spike in cross 7, flag leaf area in cross 4, while only dominance (h) component was found significant for plant height in crosses 6 and 7, number of effective tillers per plant in cross 8, peduncle length of main spike in cross 6 and harvest index in crosses 1 and 5. Both additive (d) and dominance (h) effects were significant in all the remaining crosses for all the remaining traits. While In case of late sowing, Only additive (d) effect was found significant for days to maturity and 1000-grain weight in cross 2, for days to heading and days to maturity in cross 3, for grain filling period in cross 4 and for number of grains per spike and 1000-grain weight in cross 7, while only dominance (h) effect was significant for peduncle length of main spike and grain yield per plant in cross 2, for harvest index in cross 5, for grain yield per plant and biological yield per plant in cross 6 and for number of effective tillers per plant in cross 8. Both additive (d) and dominance (h) components were significant for all the remaining crosses for all the remaining traits.
Looking to the interaction components, all the three or any one or any two interaction parameters were found significant for most of the traits in most of the crosses under both the environments indicating interaction parameters also played important role in the inheritance of majority of the character in almost all the crosses.
The classification of gene action showed importance of duplicate type of gene action for most of the characters in most of the crosses under both the environments. Under a situation of this type, it would be difficult for the breeder to get promising segregants better than parents involved through conventional breeding methods.
Magnitude of heterotic effects was high for length of main spike and number of grains per spike under both the sowing conditions. Though, high magnitude of heterotic effect was also registered for biological yield per plant and grain yield per plant under late sowing. The cross GW 9715 x K 9102 exhibited the highest standard heterosis followed by CLN 1 x GW 273 and RWP 2002-2 x LOK 1 for grain yield per plant under timely sowing. While in case of late sowing, the maximum standard heterosis was displayed by hybrid CLN 1 x GW 273 followed by RWP 2002-2 x LOK 1 and CLN 5 x GW 322. It was observed that crosses CLN 1 x GW 273 and RWP 2002-2 x LOK 1 were heterotic for grain yield per plant and majority of important traits in desirable direction under both the environments.
Either low or moderate amount of inbreeding depression in desired direction was found for developmental traits like days to heading, days to maturity and plant height. While either moderate or low inbreeding depression in undesirable direction was observed for most of the characters under both sowing conditions. The cross RWP 2002-2 x Lok 1 had significant standard heterosis and negative significant inbreeding depression. The highest significant and positive inbreeding depression for grain yield per plant under E1 was found in cross RWP 2002-2 x Lok 1 followed by CLN 5 x GW 322 and AKAW 2862-1 x MACS 2496. While in case of E2, cross CLN 5 x GW 322 showed maximum and significant inbreeding depression which was followed by CLN 1 x GW 273.
The plant height, number of effective tillers per plant, number of grains per spike, flag leaf area, peduncle length of main spike and biological yield per plant displayed moderate to higher estimates of narrow sense heritability and genetic advance expressed as percentage of mean in all the crosses under timely sowing. While in case of late sown condition, plant height, number of effective tillers per plant, number of grains per spike, flag leaf area and peduncle length of main spike showed the high values of heritability as well as genetic advance. Therefore, these characters are of great importance for the improvement of grain yield.
Under timely sowing, negative and significant association with grain yield per plant was found in hybrid RWP 2002-2 x LOK 1 for days to heading, in GW 9715 x K 9102 for days to maturity and in AKAW 2862-2 x MACS 2496 for plant height. However, significant and positive relationship was displayed between grain yield per plant with number of effective tillers per plant in all the crosses except crosses CLN 5 x GW 322 and GW 9715 x K 9102, length of main spike in AKW 770 x MP 4010 and GW 9715 x K 9102, number of grains per spike in CLN 1 x GW 273 and GW 9715 x K 9102, flag leaf area in AKW 770 x MP 4010, AKAW 2862-1 x MACS 2496, CLN 5 x GW 322 and RWP 2002-2 x LOK 1, grain filling period in AKAW 2862-1 x MACS 2496, CLN 1 x GW 273 and CLN 5 x GW 322, peduncle length of main spike in GW 9715 x K 9102, NWL 1 x GW 496, P 11616 x PBW 524 and RWP 2002-2 x LOK 1, 1000-grain weight in RWP 2002-2 x LOK 1. Positive and significant association of grain yield per plant with biological yield per plant and harvest index was observed in all the crosses except cross 3 and crosses 3 and 7, respectively. In case of late sowing, significant and negative genetic association for developmental traits was found for days to maturity in cross RWP 2002-2 x LOK 1 and for plant height in AKAW 2862-1 x MACS 2496, CLN 1 x GW 273 and P 11616 x PBW 524. While positive and significant association of grain yield per plant with number of effective tillers per plant, length of main spike, number of grains per spike, grain filling period and biological yield per plant was observed in all the crosses except cross 3 for length of main spike and cross 2 for number of grains per spike under late sowing. Further significant and positive genetic association was observed for peduncle length of main spike in AKW 770 x MP 4010 and RWP 2002-2 x LOK 1, 1000-grain weight in AKW 770 x MP 4010, P 11616 x PBW 524 and RWP 2002-2 x LOK 1 and for harvest index in P 11616 x PBW 524 and RWP 2002-2 x LOK 1. Above said yield contributing characters are useful for the indirect selection for the improvement of grain yield per plant under respective environment in bread wheat.
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