Recombination in the genus Cucurbita.

ARIOUS structural and physiological barriers to recombination in species Vhyb rids often impose rigorous limitations upon the extent to which the characters of one species may be combined with those of another. Among such barriers structural and genic imbalance resulting in the differential elimination of gametes and zygotes of recombination types has often been mentioned (ANDERSON 1939; DEMPSTER 1949; STEBBINS 1945; STEPHENS 1950). Others can be pleiotropy and linkage (ANDERSON 1939; DEMPSTER 1949) ; the multiple factor control of character differences between parental types (DEMPSTER 1949; SMITH 1950) ; developmental restrictions imposed by similar relative growth patterns (SMITH 1950) ; and affinity, a newly formulated theory which “proposes that centromeres of the same ancestral origin tend to travel to the same pole,” (WALLACE 1960). It was the objective of this investigation to determine the amount of recombination occurring in the species cross C. pepo X C. moschata, and to reveal the nature of restrictions to recombination between the two species.