ABSTRACT
These experiments were carried out at Barage Station, Qaluobia Governorate and Dokki greenhouses, Horticulture Research Institute, Giza Governorate, Egypt during the six successive seasons from 2014 to 2017. Four inbred lines of melon (Cucumismelo L.) were used in making half diallel set of crosses to determine some of the genetic parameters which are necessary in breeding programs to improve local melon (Ananas type) fruit characters and yields. The results showed significant general and specific combining ability effects for fruit characters and yield. However, the calculated ratio general combining ability (GCA) / specific combining ability (SCA) was more than unity, which indicates that the additive genetic variance component is the larger component than other types of genetic variance components. Both line 2 (P₃) and 52 (P₄) parents were found to be a good general combiner for all studied charactersThe potentiality of crossing between specific parents were detected by estimating (SCA) effects of each F1 cross combination for all studied traits. three out of six crosses exhibitedsignificant positive SCA effects for early and total yield/plant. Four out of these six crosses namely: (P1 x P2), (P1 x P3), (P2 x P3) and (P3 x P4) exhibited significant desirable positive of SCA average fruit weight and flesh thickness. Two out of the six crosses namely: (P1 x P4) and (P2 x P3) exhibited significant desirable positive of SCA effects for average fruit length and fruit diameter. Regarding to total soluble solids two of the six crosses namely: (P2 x P4) and (P2 x P3) exhibited significant desirable positive of SCA effectsindicating the possibility of combine both high yield and good quality characters. The three crosses combinations, which exhibited significant positive of SCA for yield/plant, were also combined significant, highly significant , desirable SCA effects forflesh thickness and average fruit weight. Two out of the four best crosses in early and total yield were derived from 2 (P₃) and 52 (P₄) parents that were above classified as a good general combiner for early , total yield, flesh thickness and TSS.Therefore, these parents 2(P₃) and 52 (P₄) could be used as promising progenitors for abovementioned traits either for heterosis breeding or in genetic improvements by means of selection in segregating generations. The first cross  P3 (2) x P4 (52)  was derived from good × good general combiner parents for total yield/plant and exhibited the highest mean yield, highest desirable heterosis for yield, highest desirable SCA effects (for yield and all other traits) over the mid parent and high parent in this cross (P3×P4). Regarding to heritability was high in early yield, total yield, average  fruit  weight , average fruit  length, flesh thickness and total soluble solids was( 99 %- 99 %- 99 %-99 %-98 %-99 % respectively ) while the  narrow sense heritability was intermediate or low (43 %- 7 %- 4 %- 47 %- 40 %- 4 % respectively), which indicate the potentiality of these characters to be genetically improved.  Except average fruit   width character. The broad sense and narrow sense heritability was intermediate (49.98 %) and (54 %) respectively. These results indicate that influence of the environmental factors on the expression on this character