Mean Performance and Heterosis for Yield and Fruit Traits of Tomato under Drought Conditions

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 mean performance and heterosis for yield and fruit traits for six tomato cultivars, i.e. Tan Shit Star (p < sub>1), Real Stone (p < sub>2), Pearsone Imp (p < sub>3), Super marmande (p < sub>4), 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. Two adjacent experiments were conducted. Where, the first experiment was irrigated every month (environment 1) and the second one was normally irrigated, i.e., every 2 week (environment 2). The data of the two experiments were subjected to proper statistical analysis of variance and estimate the mean performance of parents and their crosses. Data indicated that the P₆ gave the highest values for total yield per plant under drought stress and combined analysis, respectively while the cross P₁xP₄ and P₁xP₆ expressed the highest values for total yield per plant under drought stress, normal irrigation and combined analysis. Moreover the highest number of fruits was detected for the parent P₅ and the cross P₅xP₆ in drought condition, normal irrigation and combined analysis. Three, three and two crosses expressed significant or highly significant and positive heterosis relative to mid parent for fruits number in drought condition, normal irrigation and combined analysis, respectively.  Moreover, highly significant and positive better parent heterosis were detected in 3, 2 and 2 crosses in drought stress, normal irrigation and combined analysis, respectively.  It was clear that the cross P₁ x P₄ expressed the highest desirable heterosis relative to mid parent and better parent in the two environments treatments and combined analysis of them.