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Abstract The present stQdies on heterosis, combining abilities, and genetic behavio~r in Muskmelon (C~cumis melo L.) were cond~cted in the Farm of Faculty of Agriculture at Moshtohor, Zagazig Univ., Banha Branch, during the years 1981-1984. The experimental material consisted of selfed lines of five M~skmelon varieties, two loc~Jl vars. (Shahd Edfina and Bassosi), three exotic could be summarized as follows :_ 1- Genetic differences among the genotypes were highly significant for all the characters studied. f 2- Heterosis values measured as departure from the average mid~parent and better-parent were significant for all the characters studied except for avel~ge f~it weight per plant. J- Both general and specific combining abilities were highly significant for all characters studied. The additive gene effects were more important than non-additive gene effects for all characters except for yield characters. Tests for reciprocal differences were significant for all characters studied. 5- The exotic varieties, Ezeatananas and Magyarkincs were good general combiners for flowering time, number of days to maturity and yield characters. The exotic varieties, Magyarkincs and Charentais were good general combiners for fruit characters. The local variety, Shahd Edfina was a good combiner for yield characters and fruit shape index. Meanwhile, the local variety, Bas~osi was poor general combiner in comparision to the other four varieties. 6- The best combiners were presented in the crosses of (Shahd Edfina X Magyarkincs) for number of days to first male flower anthesis, (Ezeatananas X Bassosi) for days to first female or hermaphrodite flower anthesis, (Magyarkincs X Bassosi) for number of days to ma1lurity, (Shahd Edfina X Charentaia) for yield, shape index and T.S.S. characters, and (Ezeatananas X Magya~ kincs) for fruit flesh thickness. 1- The addi tive genetic variance were more important than the dominance genetic variance for all charac tera except for number of tru1 ts per plant. 8:” The average degree ot dominance was tound to be arti~l dominance tor all characterse%cept tor liumer of fruits per .plant, 1fhich showed overdom1nanoe. I ’9· The negative and pos1 tive alleles were not equa- I ly distributed among the parental popu.lat1ons in 11 cases, O-The proportion ot dominant to recess1Te genes, ruggested that the dominant genes are in excess in ~he parents. tor number of days to open the first teale or hermaphrodite flower, number of days to matuty, and yield characters. While the recessive gen •• re predominant for number of days to open the first ale nower and f:ru1 t characters. +1- All characters were tound to be under the control t:t’ one grou.p ot genes exhib1 ting dominance. a- High narrow sense her! tabili ty values were deteoted or flowering time, nLlDber of days to maturity, trui t hape index, and total soluble solids. Lowvalue ot arrow SeDse ben. tab!11 ty was obserYed tor ntaber ot :nti ts per plant.- While the average trui’li .eight per lant and lru! t fiesh thickness exhibited 1ntexmediat. arrow sense her! tab!l1 t7 Talues. J- The ae10tic tea’tllr •• ot the tlve Tar! .tie. and heir teD different JQ-br.ld. were stud1ed at ••• pha•• • The pairing ot the chroJao8Oll.es was coapl.tely normal with twelve bivalents. The chromosomeswere all small, the largest one being (39.28Mm) length. The karyotype can be classified into metacentric, submetacentric, sub-telocentric, and telocentric. Two pair of the chromosomesincluded satellites. 14- The number of days to first male nower anthesis showed significant posi tive phenotypic correlations with each of date of the first female or hennaphrodite flower anthesis, number of days to maturity, and with total soluble solids. It showed significant negative correlation with fruit flesh thickness. Date of the first female or hermaphrodite nower anthesis showed significant positive correlation with number of days to maturi ty. Meanwhile, it showed significant negative phenotypic correlations with each of fruit flesh thickness and total soluble solids. Number.of days to maturi.ty showed significant negative phenotypic correlations wi th each of frui t nesh thickness and total soluble solids. Numberof fruits per plant showed significant posi tive phenotypic correlations wi.th each of average frui t weight per pl8.l1t and total soluble solids. Fruit nesh thickness showed significant pasi tive phenotypic correlation with total soluble solids. |