The GCA and SCA effects were estimated according to [6] by the following formula:

GCAeffects ( Gi ) = gi = 1 / p + 2 [ ∑ ( Yi . + Yii ) − 2 / pY

SCAeffects ( Sij ) = Yij − 1 / p + 2 ( Yi . − Yii + Y . j + Yjj + ( 2 / ( p + 1 ) ( p + 2 ) ) Y

For estimation of heterosis in each character the mean values of the 21 F₁’s have been compared with better parent (BP) for heterobeltiosis. Percent heterosis was calculated as

H ( BP ) = [ ( F 1 − BP / 1 00 ) × BP ] [ when BP for better parent , H for heterosis ]

The significance test for heterosis was done by using standard error of the value of better parent as

SE ( BP ) = sqrt [ 3 / 2 × ( MSE ) / r ] [ MSE for Mean Squared Error ]

The values of mean sum of square for both GCA (general combining ability) and SCA (specific combining ability) were highly significant for yield per hectare, which suggests the presence of both additive and non-additive genetic variance in the population (Table 3). But the higher magnitude of GCA compared to SCA indicated predominance of additive genetic variance. The GCA component is primarily a function of the additive genetic variance. GCA of parents plays a significant role in the choice of parents. A parent with higher positive significant GCA effects is considered as a good general combiner for yield. The magnitude and direction of the significant effects for the five parents provide meaningful comparisons and would give indications to the future breeding programme.

In the present study, parent P1 also showed the greatest relative GCA effect (2.78**) followed by P3 (2.22**) for yield (Table 4). The parent P5 (−2.28**) was however a poor combiner for yield. KBG-16 was the best general combiner for total yield per vine [7] . Parent L13 showed high GCA effects for the average yield per plant [8] . Almost similar trends of additive and non-additive gene actions have been reported previously by other research groups [9] .

*Significant at 5% level; **Significant at 1% level.

*Significant at 5% level; **Significant at 1% level.

Out of 10 cross combinations 6 crosses showed positive SCA effect for yield, among them 4 crosses exhibited significant positive SCA effect (Table 4). The highest positive significant SCA effects were shown by the hybrid P1 × P3 (7.49**) followed by P2 × P3 (4.13**), P4 × P5 (4.03**) and P2 × P4 (2.95**). Thus P1 × P3 was the best combination (good × good combiner) compare to other three hybrids P2 × P3 (poor × good combiner), P4 × P5 (poor × poor combiner) and P2 × P4 (poor × poor combiner) for yield in bottle gourd. The other higher values of positive SCA effect may be considered as good specific combiner (poor × poor combiner or poor × good combiner) for fruit yield. [9] also found 3 hybrids viz., GH-10 × G-2, GH-9 × PSPL and GH-13 × G-2 exhibited significant specific combining ability effects for fruit yield. [10] reported good SCA for fruit yield. [11] reported that the parents having poor GCA for certain traits when crossed with parents having high GCA for the same traits usually generated high positive SCA effect. Similar trends were also observed in the present study e.g. P2 × P3. The parents like P2 having poor GCA for yield, when crossed with P4 having poor GCA, for this character, gave higher positive SCA effects (P2 × P4). Since a relationship seems to exist between general and specific combining ability effects, it would safely be assumed that P2 would be an outstanding parent contributing to yield through additive gene actions.

Significant difference between genotype and replication was observed in ANOVA for fruit yield (Table 3). Among ten crosses 6 combinations exhibited significant positive heterotic effect for yield of bottle gourd (Table 5). Percent of mid parent positive heterosis ranged from 7.7% to 31.8%. The highest significant positive heterosis was obtained from the cross P2 × P3 (31.8%). More than 20% mid parent heterosis was observed from 3 crosses. The highest values were observed in P2 × P3 (31.8%), P2 × P4 (25.5%) and P2 × P5 (20.5%). While [12] reported the highest heterosis over mid-parent for yield per plant was recorded in L13 × T1 (117.26%), L9 × T1 (20.68%) manifested heterosis over the standard parent (T3-Pusa Naveen).

In the case of better parent heterosis for this trait 5 crosses showed significant positive better parent heterosis. Percent of significant positive heterosis ranged from 9.4% to 20.5%. The highest significant positive better parent heterosis was exhibited for the hybrid P2 × P5 followed by P2 × P4 (18.5%). While [12] reported the yield per plant of F₁ hybrids L12 × T2 (13.80%) and L9 × T1 (8.08%) manifested heterosis over top parent. [13] stated the highest heterobeltiosis for yield was recorded in cross PSPL × NDBG-1 (106.85%). [14] got 3 best F₁ hybrids (S46 × S54, S10 × S52-7 and S54 × S52-7) showed 84.5%, 80.5% and 80% heterosis, respectively, for yield over the best parental line, S41. [15] stated three best performing F₁ hybrids LA-46 × LA-99, LA-12 × LA-76 and LA-32 × LA-37 also showed 51.8% and 125.9%, 81.8% and 121.1% and 99.1% and 200.1% higher

*Significant at 5% level, **Significant at 1% level.

yield over the better parent in kharif and summer seasons, respectively. [14] reported the best performing hybrids for yield were S36-1 × NC59812-1 and S39-1 × S1-3, with 76.4% and 58.1% heterosis over better parents, respectively. The yield per plant exhibited appreciably high amount of heterosis over the better parent, top parent and commercial control [16] .

The components of variation along with the derived genetic ratios for fruit yield (Table 6) showed that the D and H components, which measure additive and dominance variation, respectively were significant. This indicated the importance of both additive and dominance components for the inheritance of all the genotypes in bottle gourd. However, the magnitude of dominance was higher than the additive component. These results agree with that reported by [17] . The H₂ representing dominance deviation due to relative frequency of positive and negative genes was significant.

The proportion of positive effects as indicated by F value was non-significant

for fruit yield, suggesting greater frequency of dominant alleles governing this character.

The net dominance effect, obtained by the estimate h² expressed as the algebraic sum over all loci in heterozygous condition in all crosses, was significant. This revealed that substantial contribution of dominance effects was due to heterogeneity of loci.

The environmental component E, exhibited non-significant values, indicating no influence of environmental factors in the expression. However, the magnitude of E was definitely lower due to no value than the respective value of D and H₁. This also indicated that the characters were influenced less by the environment.

The average degree of dominance as indicated by the proportion (H₁/D)^1/2 was more than unity, suggesting that over dominance was operating in the expression for fruit yield of bottle gourd. [18] and [19] also found over-dominance in graphic analysis.

The ratio of H₂/4H₁ provides an estimate of the average frequency of positive and negative alleles in all the parents. A value of this ratio smaller than 0.25 studied suggested asymmetrical distribution of only the negative alleles.

The ratio of [(4DH₁)^1/2 + F/(4DH₁)^1/2 − F] estimates the relative proportion of dominant and recessive alleles in the parents. In the present study the ratio for all the characters were greater than unity, suggesting excess of dominant alleles and minority of recessive alleles i.e., asymmetrical distribution for dominant alleles in the parents.

The estimated number of effective factors (h²/H₂) was less than unity for all the attributes studied. The proportion of genes or group of genes showing dominance was very less, which could be owing to the predominant concealing effects of positive and negative effects of genes or to non-isodirectional distribution of polygene [20] .

Heritability in narrow sense was higher for fruit yield, indicating that this character was highly heritable. These results agree with that reported by [17] .

Graphical analysis of parent-offspring covariances (Wr) on array variances (Vr) is shown in Figure 1. It was observed from the Wr/Vr graph that the slope of the regression line for fruit yield was significantly below 1.0 (0.39 ± 0.15), suggesting significant non-allelic interaction for this character. The regression line intersected the Wr axis above the origin, suggested incomplete dominance to partial dominance in addition to the interaction. Here all the Wr, Vr points lay within the boundary of the limiting parabola. The relative values of Wr and Vr showed that the parent P4, P5 had the lowest value and hence contained the most dominant alleles while the parent P3 had the highest Wr, Vr values and have the most recessive alleles. The other parents fell in between suggested that the equal frequency of dominant and recessive alleles.

All the Wr, Vr points were fall within the boundary of the limiting parabola and here the parents also clustered into two distinct groups on the regression line showing diversity in the parents for this trait.