[Evidence of the unreduced diploid eggs generated from the diploid gynogenetic progeny of allotetraploid hybrids].

Following activation by UV-irradiated sperms from scatter scale common carp and without the treatment for doubling the chromosome number, the eggs generated by the diploid gynogenetic progeny (G1) with 100 chromosomes,developed into diploid gynogenetic progeny (G2) with 100 chromosomes. Both the males and females of the tetraploids with 200 chromosomes were obtained from the offsprings (G1 x AT) produced by mating the eggs of G1 with the diploid sperms from the allotetraploid hybrids. The results provided the evidence that diploid G1 is able to produce diploid eggs. In the oogonia of diploid six-month old G2, only the chromosomes in the metaphase of mitosis were observed in all slides, no bivalent chromosome being found, suggesting that the oogonia in six-month old G2 were not mature enough for meiosis I. The presence of the chromosome spreads with 100, 200 and 380 chromosomes observed in the metaphase indicated that the diploid G2 had the potential ability to generate diploid eggs with the probable mechanism of pre-meiotic endoreduplication. In contrast, the spermatocytes of G1 x AT allotetraploids had the normal chromosomal behavior with only 100 bivalents found in meiosis I. The one-year old G2 possessed the slowly developmental ovaries which stayed at the oogonium stage for a long time, in which no primary and mature oocyte was found, whereas both the females and males of one-year old G1 x AT allotetraploids had normal ovaries and testes which reached maturity and produced diploid eggs and diploid sperms, respectively. The formation of the diploid eggs generated from the diploid gynogenetic progeny makes it available to establish a diploid hybrid clonal line, and will become an important source of production of diploid eggs. In addition, the bisexual fertile G1 x AT allotetraploids enriched the types of the tetraploids.