Starting from four basic strains of Drosophila melanogaster , two laboratory strains (cn bw, Tokyo) and two isofemale lines (B-102, B-103) originated from a wild population in Texas, we constructed by repeated backcrosses through females for 20 or more generations a total of 16 strains of all possible combinations between the chromosome sets and cytoplasmic classes. Females from these 16 synthesized strains were then examined for their reproductive performance during their entire life span.—The chromosome set from the cn bw strain was found to associate with the highest female productivity when the age of females was very young, but these females ceased their reproduction and died relatively earlier, resulting in a smaller number of total progeny. The B-102 and B-103 chromosome sets, on the other hand, were associated with the lowest productivity when the females were young, but they lived and continued reproduction longer, resulting in a larger number of total progeny. The Tokyo chromosome set was associated with female productivity intermediate between the other two groups.—Cytoplasmic factors were found to affect the productivity of young females, with the cytoplasm from the cn bw strain associated with the highest productivity. Longevity was not cytoplasmically affected.—There was a clear interaction in female productivity between the Tokyo chromosome set and the cytoplasm from the Texas isofemale lines; the lifetime female productivity, as well as longevity, associated with the Tokyo chromosome set was found to increase considerably when it was substituted into the cytoplasm of the Texas isofemale line. This chromosome-cytoplasm interaction appeared to be independent of the two systems of hybrid dysgenesis.
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