Three resistance introduced varieties melon were namely, PI 140471 as p,;
PI 124111 as P₂ and PI 183227 as P₃ were used as (males) with three commercial
varieties namely Hale's Best, Honey dew and Ismaelawi (females) as susceptible
parents to achieve this investigation during 2001-2002 in the farm of EI-Kassasien
Horticulture Research Station. All the six parental genotypes and their F,'s were evaluated under the
artificial infection in open field in complete blocks randomized, with three replicates, to
investigate the relationship between peroxidase activity, lignin content, infection
severity and the nature of inheritance for this traits and the obtained results can be
summarized as following: Analysis of variance show that, there were highly significant differences for
all studied traits.       4. 5. 6.     Gene expression of infection severity, peroxidase activity and lignification of
mean performance for parents and Flhybrids were high. Additive and non-additive variances has important role in the expression of
these traits. Over dominance was governed the expression of these traits. Results of general and specific combining ability show that, the best parents
for low infection severity and high level of peroxidase activity were PI
140471; PI 183227 then PI 124111 while Ismaelawi was the best parent for
lignification, meanwhile the best F, for the above mentioned characters were
PI 140471 x tsrnaelawi: PI 183227 x Honey dew while, the
F1 PI 140471 x Honey dew exhibited the highest values for lignin content. These results could be used as markers for selection program for breeding
program for resistance against downy mildew in melon. The artificial infection in early stage of melon plants led to significant
depression for average fruit weight, fruit yield per plant and total fruit yield
per feddan, while the number of fruits per plants, flesh thickness and total
soluble solids did not significantly affected.