RESULTS AND DISCUSSION
4.4. Character associations
4.4.3. Correlation coefficient (r) between heterosis and specific combining ability (SCA) effects of crosses for 14 agronomic anti yield related trait
Correlation coefficient (r) between heterosis (over mid parent and better parent) and specific combining ability (SCA) effects of crosses have been worked out and presented in the Table 10.
Incase of mid parent heterosis the table shown that out of 14 agronomie as well as yield related characters twelve characters viz., Plant height, days to 50%
flowering, days to maturity, panicle length, tiller hill'', panicle meter'2
,grain panicle", secondary branch panicle", panicle weight, 1000-grain weight and yield plant" were exhibited significant and positive correlation with specific combining ability (SCA) effects of crosses.
On the other hand, for better parent heterosis, nine characters viz: Plant height, days to 50% flowering, panicle length, tiller panicle meter 2
,grain panicle".
secondaiy branch panicle", spikelet panicle' and yield plant" were also exhibited
significant and positive correlation with specific combining ability (SCA) effects
of crosses. Days to maturity, panicle weight and 1000-grain weight expressed
positive but insignificant correlation (Table 10).
Table 10. Correlation coefficient (r) between SCA effects and heterosis over mid parent and better parent for 14 agronomic and yield
contributing traits in rice
Character Correlation coefficient (r) --
SCA vs heterosis SCA vs heterosis
- - (over mid parent) (over better parent)
Plant height 0.266** 0.308**
Days to 50% flowering 0.284** 0.274**
Days to maturity 0.341 ** 0.214**
Panicle length 0.306* 0.378**
Tiller hilr'
0.535**0.448.**
Panicle rnete(2 0•794**
0.713**Grain panicle4
0.565**0.563**
Spikelet panicle" 0,447** 0.389**
Spikelet fertility 0,335** 0.342**
Primary branch panicl&' 0.482** 0.446**
Secondary branch panicle
d0.690*.t 0.560*
*Panicle weight 0.746** 0.68
1000-grain weight 0.801** 0.687**
Yield planf' 0,704**
0.587**pC0.5 and "p<OA
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Spikelet fertility (%) and primary branch panicle' possessed insignificant and negative correlation for both of cases.
The results are described above implied that the heterosis of a hybrid combination could be predicted reliably by specific combining ability. Such kind of close and consistent Positive relationship between heterosis and combining ability 11w eight agronon-iic characters was reported by Wang and Tang (1988).
4.4.2. Heterosis in relation combining ability effects
4.4.2.1. Heterosis in relation to general combining ability (GCA) effects
Information on combining ability of the parents and the extent of heterosis between them would be uselul to find out the contribution of the parents.
Desirable heterosis over one or both the parents for agronomic and yield related characters could emerge from the crosses involving parents in one of' the six combinations of GCA effects, i.e. high x high (1-ixH), high x average/average x high (HxA), high x low / low x high (1-1 x L), average x average (A x A), average x low/low x average (A x L) and low x low (LxL). On the basis of the above principle, heterosis over mid and better parents in relation to parental GCA effects are presented in Table 11 and Table 12, respectively.
4.4.2.1.1. Plant height
The data in the Table 11 showed that out of 29 significantly heterotic hybrids over mid parent, three combinations were found in desirable direction over better parent which were belonged to LxL type parental GCA combination. On the other hand, out of the ] S heterotic combinations six were observed in desirable direction of which one belonged to HxL type, one belonged to AxA type, two belonged to AxL type and three of them belonged to Lxi.. type parental ('JCA combinations (Table II). The results indicated that good general combination for dwartuiess was evolved from high x low, average x average, average x low and low x low general combiner parents and there additive x additive, additive X
dominance and dominance x dominance type of gene action was predominant for this trait.
4.4.2.1.2. Days to 50% flowering
Among the 35 significant heterotic crosses oniy16 were found in desirable direction over mid parent of whom six belonged to HxL and rest 10 belonged to LxL type parental GCA combination. Likewise, 29 hybrids out of 38 possessed significant heterosis (in desirable direction) over better parent (Table 12) and which were distributed as: four of HxH, 14 of HxL and 11 of LxL type parental GCA combination (Table 12). The results provided information that additive x additive, additive x dominance and dominance x dominance type of gene action was predominantly responsible for this trait.
4.4.2.1.3. Days to maturity
Out of 10 significant crosses (in desirable direction) four belonged to HxL and six belonged to LxL type GCA combination in respect of mid parent heterosis (Table II). Similarly, for better parent heterosis three belonged to HxL and six that of LxL indicating that for both the cases this trait are predominantly governed by additive x dominance and dominance x dominance type of gene action.
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i'able 11. Heterosis over mid parent (in desirable direction) in relation to parental GCA effects for 14 agronomic and yield contributing traits in rice
Character Nuniberofhctcrotic crosses (over mid parent) in Total different parental GCA combinations
HxH HxA HxL AM ,kxi Lxi
Plant height 0 0 0 0 0 3 3
Days to 50% u1otring 0 0 6 0 0 10 16
Days to maturity 0 0 4 0 0 6 10
Paniele length 6 5 11 I 2 6 3!
TilkrhilF1 2 3 0 0 0 0 5
Panicle inetcr2 3 2 0 0 0 0 5
Grain panielC' 3 5 I 1 0 0 10
Spikelet panickY' 2 15 0 2 1 0 20
Spikelet fertility 4 3 0 0 0 0 7
Prinian branch panicle 5 7 2 I 2 0 17
Secondary branch panicle' 1 6 2 2 3 0 14
Panicle weight 0 8 0 12 I 0 21
1000-grain weight 3 8 3 0 6 0 20
Yield plani' 0 9 0 15 5 0 29
Total 29 71 29 34 20 25 208
I I-}i'h (,CA. LLov GCA. A- Accngc GCA
Table 12. Heterosis over better parent (in desirable direction) in relation to parental GCA effects for 14 agronomic and yield contributing traits in rice
Character Number of heterotic crosses (over better parent) Total in different parental GCA combinations
HxH Flx,t HxL AxA AxL IL
Plant height(em) - 0 0 1 0 2 3 6
Days to 50% flowering 4 0 14 0 0 11 29
Days to maturity 0 0 3 0 0 6 9
Panicle length (cm) 6 4 5 I 2 2 20
jilter hilU' I I 0 0 0 0 2
Panicle meter 0 1 0 C) 0 0 1
Grain panicIe 2 3 1 I 0 0 7
.Spikelet panicl&' 2 12 0 0 0 0 14
Spikelet fertility (%) 3 I 0 0 0 0 4
Primary branch panicle1 3 2 0 0 0 0 5
Secondary branch panicl&' 2 3 1 2 0 0 $
Panicle weighg) 0 5 0 6 1 0 12
1000-grain wcight(g) I 0 0 0 0 0 1
Yield planL1 0 7 0 12 2 0 22
Total 24 39 25 22 7 22 139
I 1 -IIiith UUA, I.Lc,v GCA. A Asciagc GCA
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4.4.2.1.4. Panicle length
For mid parent heterosis out of 3 I desirable crosses six were 1-hi-I, five were HxA, II were HxL, one were AxA, two were AxL and six were LxL(Table 11).
On the other hand, in respect of better parent heterosis six belonged to lix! I, four belonged to HxA, five belonged to lExL, one belonged to AxA, two belonged to AxL and two belonged to I.A. (Table 12). The results suggesting that the trait panicle lengths irrespectively controlled by additive x additive, additive x dominance and dominance x dominance type of gene action.
4.4.2.1.5. Tiller hilF'
Out of' five significant crosses two belonged to HxH and three belonged to 11th type GCA combination in respect of mid parent heterosis (Table 11). Similarly, br better parent heterosis out of two significant crosses one belonged to I-Ext-I and one belonged to HxA type GCA combination indicating that for both the cases this trait are predominantly governed by additive x additive type of gene action.
4.4.2.1.6 Panicle meter -
Among the seven significant heterotic crosses only five were found in desirable direction over mid parent of whom three belonged to I lxii and two belonged to HxA type parental GCA combination (Table II). Likewise, only one hybrid out of nine possessed significant heterosis (in desirable direction) over better parent and belonged to llxA type parental GCA combination (Table 12). The results provided information that additive x additive.
4.4.2.1.7. Grain panicle4
For mid parent heterosis out of 10 desirable crosses three were 1-lxI-1, five were HxA, one were T-IxL, and one were AxA type parental GCA combination ('fable 11). On the other hand, in respect of better parent heterosis two belonged to HxH, three belonged to I-lxA, one belonged to HxL and one belonged to AxA type parental GCA combination (Table 12). The results suggesting that the trait
panicle length irrespectively controlled by additive x additive and additive X dominance type of gene action.
4.4.2.1.8 Spikelet panicle-1
Out of 20 significant crosses (in desirable direction) two belonged to HxH, 15 belonged to HxA, two belonged to AxA and one belonged AxL type GCA combination in respect of mid parent heterosis (Table 11). Similarly, for better parent heterosis two belonged to I-lxH and 12 that of UxA type parental GCA combination indicating that for both the cases this trait is predominantly governed by additive x additive and additive x dominance type of gene action.
4.4.2.1.9. Spikelet fertility (%)
Among the 14 significant heterotic crosses only seven were found in desirable direction over mid parent who of them four belonged to HxH and rest three belonged to HxA type parental GCA combination (Table 11).
Likewise, out of 13 hybrids four possessed significant heterosis (in desirable direction) over better parent (Table 12) and which were distributed as: four of l-lxl-1, and one type parental GCA combination (Table 12). The results provided information that additive x additive type of gene action was predominantly responsible for this trait.
4.4.2.1.10. Primary branch panicle-'
For mid parent heterosis out of 17 desirable crosses were distributed as: five HxIl. seven I-hA, two HxL. one AxA and two AxE, type parental GCA combination (Table 11). On the other hand, in respect of better parent heterosis only three belonged to 1-Ixil and one belonged to UxA (Table 12). The results suggesting that the trait panicle length irrespectively controlled by additive x additive and additive x dominance type of gene action.
III
4.4.2.1.11. Secondary l)ranch panicl&'
Out of 10 signilicant crosses (in desirable direction) four belonged to HxL and six belonged to LxL type GCA combination in respect of mid parent heterosis (Table II). Similarly, for better parent heterosis three belonged to HxL and six that of Lxi. (Table 12) indicating that for both the cases this trait are predominantly governed by additive x dominance and dominance x dominance type of gene action.
4.4.2.1.12. Panicle weight
Out of-2 I significant crosses (in desirable direction) eight belonged to HxA and 12 belonged to AxA and one belonged to AxL type of GCA combination in respect of mid parent heterosis (Table 11). Similarly, for better parent heterosis live belonged to 1lxA, six that of AxA and only one belonged to AxL type of GCA combination (Table 12) indicating that for both the cases this trait are predominantly governed by additive x additive and additive x dominance type of gene action.
4.4.2.1.13. 1000-grain weight
Among the 20 significant heterotic (in desirable direction) crosses three belonged to HxH and eight belonged to 1-hA, three belonged to HxL and six belonged to AxL type parental GCA combination (Table 11). Only one cross was found heterotic (in desirable direction) over better parent and it belonged to lixil, type parental GCA combination (Table 12). The results provided information that additive x additive and additive x dominance type of gene action was predominantly responsible for this trait.
4.4.2.1.14. Yield plant'
For mid parent heterosis, out of 29 desirable crosses nine were HxA. 15 were
AxA and five were AxL (Table 11). On the other hand, in respect of better parent
heterosis out of 21 seven belonged to H.xA, 12 belonged to AxA two belonged to
AxL type parental OCA combination (Table 12). The results suggesting that the trait pariicle length irrespectively controlled by additive x additive and additive x dominance type of gene action.
A feasible genetic basis provided by Langham (1961) for the of high x low (H x U combirudion was supported by this experiment.
Similar, better hybrid performance of H with L parents was reported by earlier workers like, Bashar (2002) in rice, Mian and BahI (1989) in check pea and Singhet. al., (1983) in pigeon pea.
Salam et at (1996) reported that good x poor, poor x poor combiners for grain yieldlplant, spikelets/panicle, panicle length, panicle/plant and 1000-grain weight indication overdominance and epistasis gene actions for these characters.
However, in general the order of cross frequency over better parent heterosis was observed as high x average > high x low > high x high GCA of parent. The results are in full agreement with the reports of Flariprasanna, ci. at. (2006).
Results indicated that the superiority of high x low crosses may be due to the fbct that such a cross can result in strong transgressive segregants for the desired traits and due to segregation of genes with strong potentials and their specific buffers (I1ongham, 1961). Also, irrespective of residual genetic background, high genes express nearly same phenotypes when they are homozygous or heterozygous. But low genes can express their residual genetic background (Hariprasanna, el. of..
2006). Thus, high x high or high x low crosses usually result in situations resembling essentially their parents whereas high x low crosses produced heterozygous genotypes, which express high effects and consequently are superior to both the parents.
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