الفهرس 
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Abstract
The present investigation (a complete dialell F1 cross experiment) was carried out at the Experimental Farm and Germplasm Preservation Laboratory of Research Station of Misr Hytech Seed International Company, Giza Governorate, Egypt, during the two winter seasons of 2013/2014 and 2014/2015 to study mean performance and relative superiorly type of gene action controlling the inheritance of different traits in cucumber. The obtained results of this investigation will be discussed into the following topics:
1. Analysis of variance
The analysis of variance for genotypes was found to be highly significant for all studied traits, indicating the presence of the true differences among these genotypes under study.
Mean squares due to parents were found to be highly significant and/or significant for all studied traits, except for visual fruit quality and number of fruits/node. These findings indicated that parental inbred lines differed in their mean performances in most studied traits. At the same time, the insignificance of parent’s mean squares which were detected for the mentioned exceptional traits indicated that the studied parent’s materials were equal in visual fruit quality and number of fruits/node.
The crosses mean squares were found to be highly significant for all traits studied, except for visual fruit quality and number of fruits/node.
The variation due to parents vs. hybrids was highly significant for all the characters except number of days to 1st picking, visual fruit quality and fruit diameter indicating significant heterotic response.
2. Mean performances
The results showed that some parents had significant longer plants, i.e. P3 and P4 230, and 221.7 cm, respectively. Meanwhile, the parent P1 gave the lowest value for plant length 175 cm.Reciprocal hybrid P4×P3 exhibited the highest genotype for this being 266.7 cm. On the other hand, the cross P1×P2 and P2×P1 showed the shortest main plant length 178.3 and 176.3 cm, respectively.
Some genotypes had higher significant number of leaves per plant, i.e. P1 and P3 being 30.67 and 28.33, respectively, compared. The P2 had the lowest number of leaves per plant 20.0 leaves. For F1 hybrids, the results referred that the hybrids P4×P2 displayed the highest number of leaves per plant 33.67.
The results showed that P1 had the highest significantly leaf area 11090 cm2 compared with other parent. P2 gave the lowest average for this trait being 4648 cm2. The two F1 combinations P3xP4 and P1xP5 gave the highest leaf area 14790 and 14240 cm2, respectively. Both reciprocal hybrids P4×P1, P3×P4 gave the highest mean performance they recorded 15330 and 14530 cm2, respectively.
Some genotypes had significant significantly the fewest number of days, i.e. P1 and P2 both showed the same number of days to first picking 32 days after transplanting compared with other genotypes such as P3 and P5 with number of days to the first picking 43 and 42, respectively. The results referred that the hybrids P3×P1 and P4×P3 were faster on the same day 32 days. The results refer that the hybrids P1×P5 and P5×P2 were first on the same a picked day 41days
The results showed that some genotypes had higher visual quality score, i.e. P5 and P4, 8 and 7.33, respectively compared with other genotypes such as P2 and P1, 6 and 6.33, respectively. The results referred that the hybrids P3×P4 followed by P3×P2 gave the lowest main visual fruit quality score, 5.67 and P3×P5, P3×P1 and P4×P3 gave the same visual fruit quality, 6.0.
The results revealed that lines P1 2.33 and P2 and P4 same value 2.0 had higher produced per node without significant differences between them 2.33 and 2.0 compared with the other tested genotypes. In the meantime there was no significant difference between P5and P3 1.33 and 1.67. The hybrids P2×P1, P3×P1 and P1×P2 gave the highest fruit number with significant differences among them 2 and 1.67 respectively which the fewest number of fruits without significant differences them P1×P3, P3×P5, P4×P5, P4×P1, P4×P3 and P5×P4 on the same value 1.0.
The results showed that parent P1 had significantly the highest number of fruits/plant 23.67 compared with other genotypes. Results referred that the hybrids P3×P1 displayed the highest number of fruits/plant 24.40 followed by P2×P4 and P2×P1 which expressed high of number of fruits/plant 22.33.
The results showed that P4 genotypes had significantly the higher fruit weight 106.5 gm compared with other parents. The hybrid P4×P1 displayed the fruit weight 120.09 gm.
The results showed that parent P1 had significantly the heaviest fruit yield/plant which recorded 2.040 kg compared with other parents. Two hybrids P2×P4 and P2×P1 displayed the heaviest fruit yield/plant 2.420 and 2.430 kg, respectively.
The results showed that parents P5, P4 and P3 had significantly the tallest fruits 15.00, 14.33 and 14.00 cm, respectively compared with other parents. Three hybrids P1×P4, P4×P5 and P4×P2 displayed the highest fruit length 17.03, 16.89 and 16.44 cm, respectively.
The results showed that parents P2 and P5 had significantly the lowest fruit diameter 2.780 and 2.670 cm, respectively compared with other parents. On the other context, the crosses P2×P5, P3xP5, P5×P2, and P5×P4 showed the thinnest fruit diameter.
The results showed that P3 exhibited significantly the highest TSS value 3.0% compared with other parents. The results refer that the hybrid P4×P3 displayed the highest value for this trait.
Combining abilities
Analysis of variance for combining ability
The mean squares associated with general combining ability were highly significant for all traits. However, the mean squares associated with specific combining ability were highly significant for all traits except for visual fruit quality. The mean squares associated with reciprocal were highly significant for visual fruit quality and number of fruits/node.
For all traits, general and specific combing ability mean squares were highly significant for visual fruit quality. Hence, GCA/SCA ratio was used as measure to reveal the nature of genetic variance involved.
The ratios of (GCA/SCA) exceeded the unity were detected for all studied traits except number of leaves/plant. In the same context, the significant GCA were detected for visual fruit quality, while, insignificant mean square were found for this character. On the other hand, these ratios were less than the unity and detected in number of leaves/plant indicating the non-additive types of gene action were greater importance in the inheritance.
General, specific combining ability effects
General combining ability effects
General combining ability effects computed herein were found to be differed significantly from zero in all cases. High positive values would be interest under all traits studied in question except number of days to 1st picking which high negative values would be useful from the breeder’s point of view.
The parental inbred line P1 exhibited significant positive ( ) effects for leaf area, number of fruits/plant, fruit yield/plant and fruit diameter indicating that this inbred line could be considered as a good combiner for developing high yield genotypes.
The parental inbred line P2 showed significant positive ( ) effects for number of fruits/plant, fruit yield/plant, and fruit length, indicating that this line could be considered as a good combiner for developing high yield with high length. Also, it gave undesirable ( ) effects for all traits.
The parental inbred line P3 seemed to be good combiner for number of days to 1st picking, visual fruit quality and TSS On the contrary, it expressed significant undesirable or insignificant ( ) effects for the rest traits.
The parental inbred line P4 showed significant desirable ( ) effects for all traits, except visual fruit quality, number of fruits /node, number of fruits/plant, and fruit yield/plant. This parent can be used for improve fruit quality.
The parental inbred line P5 seemed to be the best combiner for number of days to 1st picking, visual fruit quality and number of fruit/node. However, it gave undesirable ( ) effects for other traits.
Specific combining ability effects and reciprocal (rij) effects
For plant length, four F1 crosses P1×P4, P2×P3, P2×P4 and P2×P5 and two reciprocal crosses P5×P2 and P5×P4 exhibited highly significant positive desirable (Ŝij) effects and reciprocal (rij) effects, respectively. While, negative and/or insignificant (Ŝij) effects were detected for respect crosses.
With regard to number leaves/plant, the two F1 crosses P2×P4 and P2×P5 as well as the two reciprocal crosses P5×P2 and P5×P4 exhibited the highest desirable (Ŝij) effects and the reciprocal (rij) effects, respectively.
For leaf area, five F1 crosses, P1×P4, P1×P5 P2×P4, P2×P5 and P3×P4, as well as P2×P1 and P5×P4 exhibited significant positive ( ) effects and the reciprocal (rij) effects, respectively. With regard to days to number of days to 1st picking, the F1 cross P3×P4 as well as the three crosses P2×P1, P3×P1 and P5×P1 expressed significant negative (Ŝij) effects and reciprocal (rij) effects, respectively.
As for number of fruits/node, none of F1 crosses exhibited significant positive (Ŝij) effects. For number of fruits/plant the most desirable significant positive (Ŝij) effects and the reciprocal (rij) effects were expressed by the F1 crosses P1×P3, P2×P4 and P4×P5 and the reciprocal cross P5×P1, respectively.
With regard to fruit weight, the two F1 crosses P3×P4 and P3×P4 as well as the reciprocal cross expressed significant positive (Ŝij) effects.
As for fruit yield/ plant, (P4×P3)the four F1 crosses P1×P3, P2×P4, P2×P5 and P4×P5 as well as the reciprocal crosses P4×P1, P4xP2, P4xP3 and P5xP3 expressed significant positive (Ŝij) effects and the reciprocal (rij) effects, respectively.
For fruit length, two F1 crosses i.e. P1×P4, and P2×P3 and the four reciprocal crosses P5×P1, P3×P2, P4×P3 and P5×P4 exhibited significant positive (Ŝij) effects and reciprocal (rij) effects, respectively.
With regarding to fruit diameter, the reciprocal cross P5xP4 exhibited significant positive reciprocal (rij) effects.
As for TSS, the F1 crosses P1×P2, P1×P3, P1×P5 and P4×P5 as well as the reciprocal crosses P5×P1, P4×P2, P4×P3 and P5×P45 exhibited significant positive (Ŝij) effects and reciprocal (rij) effects, respectively.
Heterosis effects
Significant positive heterotic effects relative to better parent’s values may be interest for most traits.
Regarding to plant height, values of useful heterotic effects ranged from 14.59 to 42.73 relative to MP % in crosses P2×P1 and P4×P2, respectively. On the same context, the useful heterobiltosis effects ranged from 10.53 to 18.79 in the crosses P2×P4 and P4×P5, respectively. Twelve crosses relative to MP and six hybrids relative to BP expressed significant positive heterotic effects for this trait.
For number of leaves/plant, seven and two crosses exhibited significant positive heterotic effects relative to MP and BP, respectively. The most desirable heterotic effects were detected by crosses P2xP5 and P4xP2 which gave useful heterosis relative to MP and BP.
For leaf area, all hybrids, except P5×P4 expressed significant positive heterotic effects relative to BP and MP. The highest positive heterotic effects were detected by cross P3×P2 compared to BP and MP.
For number of days to 1st picking, the hybrids tended to deviate towards earliness especially in the reciprocal crosses P3×P1 and P4× P3 relative to MP. Meanwhile, no crosses showed negative heteroiltosis (BP) in this trait.
For visual frit quality zero crosses compared to MP and BP expressed significantly positive heterotic effects. However, only the two crosses P3×P4 and P3×P5 gave negative heterotic effects and the rest crosses did not differ significantly from MP and or BP.
Zero crosses exhibited positive significantly positive effects relative to MP and or BP for number of fruits/node. Also, the crosses gave undesirable heterotic effects relative to BP and MP, respectively.
Regarding to number of fruits/plant, fifteen crosses relative to MP and two hybrids relative to BP expressed significant positive heterotic effects for this trait.
The most desirable heterotic effects was detected by cross P2×P4 and which gave useful heterosis relative to MP and BP.
As for fruit weight, five and two crosses exhibited significant positive heterotic effects relative to MP and BP, respectively. The most desirable heterotic effects were detected by crosses P2×P5 and P2×P1 which gave useful heterosis relative to MP and BP.
For fruit yield/plant, ten and two crosses exhibited significant positive heterotic effects relative to MP and BP, respectively. The most desirable heterotic effects were detected by crosses P2xP4 and P2×P5 which gave useful heterosis relative to MP and BP.
For fruit length, eight and five crosses exhibited significant positive heterotic effects relative to MP and BP, respectively. The most desirable heterotic effects were detected by crosses P1xP2, P1xP4, P1xP3, P4xP5, P4xP1 and P4xP2 which gave useful heterosis relative to MP and BP.
For fruit diameter, the three crosses P1xP5, P4xP2 and P5xP3 exhibited significant positive heterotic effects relative to MP. Meanwhile, the all crosses showed undesirable heterotic effects relative to BP.
For TSS, twelve and five crosses exhibited significant positive heterotic effects relative to MP and BP, respectively. The most desirable heterotic effects were detected by the crosses P1xP2, P1xP5, P2xP1, P5xP1 and P4xP3 which gave useful heterosis relative to MP and BP.
Potence ratio
With respect to plant length, there were partial dominance was defined in the seven crosses P1×P3, P1×P5, P2×P3, P3×P1, P5×P1, P3×P2 and P5×P2, and seven crosses showed over dominance towards the tallest parent, i.e. P1×P2, P4×P5, P4×P1, P3×P2, P4×P2, P5×P3 and P5×P4. Meanwhile, the rest crosses showed over dominance towards the short parent.
Concerning number of leaves/plant, thirteen crosses expressed over dominance five of them were over toward the high parent, i.e. P3×P4, P3×P5, P3×P1, P3×P2 and P4×P2. However the partial dominance was detected from the remaining crosses.
As for as leaf area, only the cross P2×P1 expressed partial dominance. However the remaining values were in the range of over dominance for this trait. Also, ten crosses, i.e. P1×P2, P1×P3, P1×P4, P1×P5, P3×P2, P4×P2, P5×P2, P4×P3, P4×P3 and P5×P4 showed over dominance toward high parents for this trait.
Concerning number of days to 1st picking, two crosses P1× P2 and their reciprocal P2×P1 as well as the cross P2× P4 expressed absent of dominance. On the other hand, the cross P3× P1 showed complete dominance. Seven crosses, i.e. P1×P3, P1×P5, P2×P3, P2×P5, P5×P1, P3×P2 and P5×P2 showed partial dominance. Meanwhile, the remained crosses showed over dominance
With respect to visual fruit quality, four crosses P2×P3, P2×P4, P2×P5, P4×P5 and P5×P3 expressed absent of dominance. Meanwhile, the crosses P1×P4, P2×P1 and P4×P1 showed complete dominance. The three crosses, P1×P5, P5×P1, and P5×P2 expressed partial dominance. However the other crosses showed over dominance.
For number of fruits/node, three crosses, i.e. P2×P4, P4×P2, and P3×P1 expressed absent of dominance. Meanwhile, the crosses P1×P5, P2×P4, P2×P1, P5×P1, P3×P2 and P5×P2 showed complete dominance. However, over dominance were detected in the remaining crosses.
With respect to number of fruits/plant, thirteen crosses P1×P5, P2×P3, P2×P4, P2×P5, P3×P4, P3×P5, P4×P5, P3×P1, P4×P1, P5×P2, P4×P3, P5×P3 and P5×P4 expressed over dominance. However, the remaining crosses values showed partial dominance for this trait.
As for as fruit weight, partial dominance were detected in the crosses P1×P4, P2×P3, P3×P5, P4×P5, P3×P1, P5×P3 and P5×P4. However, the remaining crosses showed over dominance for this trait.
Regarding to fruit yield/plant, six crosses P1×P2, P1×P3, P1×P5, P4×P1, P3×P2 and P4×P2 possessed the partial dominance However, the remaining crosses showed over dominance for this trait.
For fruit length, two crosses, i.e. P1×P3, and P5×P3 expressed complete dominance. However, over dominance were detected in the remaining crosses except P3×P1, P5×P1, and P5×P3 which partial dominance were detected. With respect to fruit diameter, four crosses P1×P3, P2×P1, P3×P1 and P3×P2 expressed absent of dominance. Meanwhile, the crosses P1×P5 and P3×P4 showed complete dominance. The seven crosses, P2×P5, P4×P1, P4×P2, P5×P2, P4×P3 and P5×P3 expressed over dominance. However the other crosses showed partial dominance.
With respect to TSS, the cross P5×P2 expressed complete dominance. Meanwhile, the crosses P1×P2, P1×P5, P2×P5, P3×P4, P2×P1, P5×P1, P4×P3 and P5×P4 showed over dominance. However the other crosses showed partial dominance.
Heritability:
High heritability values in broad-sense were detected for all traits, TSS, Plant length, number of fruits/plant, Leaf area, and Fruit yield/plant Table 14. For the exceptional case, moderate heritability values were obtained. The highest estimate of heritability was 98.64% for TSS, while the lowest heritability (in broad-sense) was detected for Fruit length (55.4%). Heritability in a narrow sense was computed according to Mather’s procedure on the basis of F1 and its parents. High heritability in narrow sense was detected for number of fruits/plant, Fruit diameter, TSS and Fruit yield/plant, while the low heritability values in narrow sense were detected for the leaf area and number of days to 1st picking (8.3, 22.6, respectively), due to the high value of the mean square GCA. Non additive gene effects were found to be the major contributing factor in these traits. On these assumptions, heritability in the narrow-sense was expected to be low, the exception which was not realized in the present study.
Phenotypic and genotypic correlation:
For plant height, it showed significant positive correlation with number leaves/plant, leaf area, Fruit weight, fruit length and TSS but it had significant negative correlation with number of fruits/plant and number of fruits/node traits. Whereas, number of leaves/ plant had significant positive correlation with leaf area, fruit weight and fruit diameter on the other side, the negative correlation was detected between the mentioned trait and number of fruit/plant. Regarding leaf area, results showed significant positive correlation with Fruit diameter. Whereas, it had non-significant correlation with other traits. Data also showed that number of fruits/plant had significant positive correlation with fruit yield/plant and number of fruits/node but it had highly significant negative correlation with number of days to 1st picking and visual fruit quality. As for fruit weight, positive and significant correlation coefficient estimates were found between fruit weight and fruit yield/plant, fruit length and fruit diameter. While it showed non-significant correlation with other traits.
Concerning number of fruits/plant, it showed highly significant positive correlation with number of fruits/node. In the same time, fruit yield/plant showed insignificant positive or negative correlation with other traits. Data also showed that fruit length and/or number of days to 1st picking showed significant positive correlation only with total visual fruit quality. On the other hand, they gave negative correlation with number of fruits/node.
Regarding to number of fruits/plant, results showed significant positive correlation with fruit yield/plant and number of fruits/node. Such data showed that fruit weight had significant positive correlation with fruit length and fruit diameter.
As to fruit yield/plant, positive and significant correlation coefficient estimates were found between number of fruits/node. Concerning number of fruit length, it showed highly significant positive correlation with visual fruit quality. Data also showed that fruit diameter showed significant positive correlation only with TSS The positive genotypic correlation was detected between number of days to 1st picking and visual fruit quality. The other cases showed either significant negative correlation or insignificant correlation.