This study was carried out during three successive summer seasons from
2002 to 2004 at Kaha Vegetable Research Station, Kalubia, Egypt. Genetic
parameters such as combining ability, heterosis and correlation were studied in 15 F1
hybrids obtained by diallel mating of 6 tomato cultivars viz., Cal Ace; Castle rock; Peto
86; Chico III; Tallalakhin and Super Strain B. Significant differences for general and
specific combining ability (GCA and SCA) were obtained for fruit set %, early and total
yield, number of fruits per plant, average fruit weight, fruit length, fruit diameter,
number of locules per fruit, flesh thickness, fruit firmness and total soluble solids
(T.S.S.) content. Results indicated that both additive and non-additive gene action are
important for this trait. The GCA: SCA ratios were higher than unity for all the studied
characters, indicating that the additive gene action is more important than non-
additive gene action in inheritance of these traits. The results showed also the
importance of additive gene action in the inheritance of ascorbic acid and fruit acidity
content. The GCA illustrated that the cultivars Chico III, Peto 86 and Super Strain B
are the best combiners to improve the fruit set and total yield during the summer
season. While the cultivars Peto 86 and Chico III are the best combiners to improve
the early yield, flesh thickness, fruit firmness and reduce the number of locules per
fruit. Among the hybrids, Castle rock x Peto 86; Cal Ace x Tallalakhin; Castle
rock x Tallalakhin; Peto 86 x Chico III; Castle rock x Chico III and Cal Ace x Super
Strain 8 were recommended for the development of high fruit setting ability. Moreover,
the best crosses had the early yielding were (Cal Ace x Chico III; Peto 86 x Chico III;
Castle rock x Peto 86; Cal Ace x Peto 86) and for total yield were (Cal Ace x Chico III;
Castle rock x Chico III; Tallalakhin x Super Strain B; Peto 86 x Chico III; Castle rock x
Peto 86) respectively. The hybrid Peto 86 x Chico III gave the highest value for
number of fruits per plant, flesh thickness, fruit firmness and lowest number of locules
per fruit. Higher heterosis was noticed by the crossing with parents having high
GCA status for early and total yield, average fruit weight, number of locules per fruit,
flesh thickness and fruit firmness. Positive correlation was found between early yield and fruit set % and
between total yield and both of fruit set %, number of fruits per plant, average fruit
weight, fruit length and diameter. Also, positive correlation was found between
average fruit weight and both of fruit length, fruit diameter and flesh thickness and
between flesh thickness and fruit firmness. Moreover, negative correlation was found
between average fruit weight and number of fruits per plant and between number of
locules per fruits and both of Fruit firmness and flesh thickness.