الفهرس 
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Abstract
The present study was carried out in a private farm, Kaha city, Kalyobiya Governorate, Egypt during summer seasons of 2015 and 2016 to study the genetic behavior of some economic traits for six tomato cultivars grown under normal irrigation and drought stress. This investigation was a half diallel F1 cross experiment to induce genetic variability by hybridization and evaluation and selection for best genotypes of tomato compared with the parents under drought conditions and normal irrigation.
The six parental genotypes of tomato (Solanum Lycopersicum), i.e. Tan Shit Star (p1), Real Stone (p2), Pearsone Imp (p3), Super marmande (p4), Tomato Golden (p5) and Peto mech (p6) and their F1S hybrids were planted in successive summer plantings of 2016 under open field conditions using randomized complete block design (RCBD) with three replicates. Each experiment was designed in a randomized complete block design (R.C.B.D) with three replications. Each replication block had 21 plots (sex parental verities and their 15 F1 hybrids) under either drought or normal irrigation. The plot (experimental unit) was one ridge of 10.5 meter in length and the distance between plants was 50 cm apart, therefor, the plot contained 21 plants. Treatments in each replicate (parents + F1s) were randomly assigned to plots.
Three plants were selected excluding border plants for recording the observation. These observations were in vegetative traits viz., stem length, number of branches, number of leaves, leaf area, plant fresh and dry weight; flowering traits viz., number of days from planting date to first flower anthesis and fruit set %; yield traits viz., fruits number and total fruit yield per plant as well as fruit traits viz., average fruit weight, length, diameter, total soluble solids percentage, total sugars and total polyphenols content in the fruit.
The obtained result could be summarized as follows:
5.1. Analysis of variance and mean performance.
• The results showed that highly significant genotypes mean squares were obtained for all vegetative traits under drought stress and normal irrigation as well as combined analysis. Moreover, genotypes x environment mean squares were high significant for all vegetative traits.
• The highest values of stem length, branches number, leaves number and area, fresh weight and dry weight were detected for the parent P5, P2, P2, P6, P5 and P4, respectively under normal irrigation; and P5, P6, P2, P6, P5 and P4, respectively under stress condition.
• The crosses P2xP5, P2xP4, P2xP4, P1xP3, P2xP4 and P2xP4 expressed the highest values of stem length, branches number, leaves number and area, fresh weight and dry weight, respectively under non-stress conditions; and the crosses P2xP5, P2xP4, P2x P4, P2xP6, P2xP4 and P2xP4, respectively under stress conditions.
• Highly significant genotypes mean squares were obtained for all fruit and yield traits under drought stress and normal irrigation as well as combined analysis. Moreover, genotypes x environment mean squares were high significant for all yield traits.
• The parental lines P5, P6, P2, P3, P4, P5, P1 and P1 expressed the highest mean values for fruits number/ plant, fruits yield/plant, fruit length, fruit diameter and fruit weight, TSS%, total sugars (%) and total polyphenol contents, respectively under normal irrigation and P5, P5, P2, P3, P4, P5, P1 and P4 respectively under drought stress.
• The crosses P5xP6, P1xP4, P2xP5, P3xP5, P1xP3, P2xP3, P2xP4 and P3xP5 exhibited the highest mean values for fruits number/ plant, fruits yield/plant, fruit length, fruit diameter and fruit weight, TSS%, total sugars (%) and total polyphenol contents, respectively under normal irrigation water; and P5xP6, P1xP4, P2xP3, P3xP5, P1xP3, P2xP3, P2xP5 and P3xP5 under drought stress.