INHERITANCE OF FERTILIZING ABILITY IN MALE TETRAPLOID RAINBOW-TROUT (ONCORHYNCHUS-MYKISS)

Males presumed tetraploid were obtained from the previously reported mating of eight first-generation tetraploid sires with a common pool of diploid females and subsequent treatment of the eggs by heat shock. Sperm samples collected from these males and from diploid controls were used for cytometric measurements and fertilization tests. The results showed that one-third of the tested males performed like the diploid controls, which led to the assumption that these individuals arose from spontaneous androgenesis. Among the other males, whose performances were in line with their presumed tetraploid nature, important familial differences were observed and correlated to the performances of the corresponding parental SiTes. The estimate of the sire-son regression for fertilizing ability (b=0.4+/-0.1) was indicative of an important inheritance allowing efficient improvement of this character by selection.