Abstract
The present paper describes some cytological investigations regarding meiosis in PMCS and the number of chromosomes and fertility of G2-G4 plants (2nd to 4th generation) that originated from artificially synthesized forage rape (B. napus). It was shown that chromosomal behavior of the progenies from surely-selfed C0-1 (Chinese cabbage "Shlgatsu" x cabbage "Successron") was very irregular and that of the progenies crossed with commercial varieties of rape (Norin-16 & France-12) was considerably stable, through observations on meiosis in PMCS of many plants with 2n=38 or 38 ± X(Tables 1, 2, 3, 4, 8, and 9). Self fertility of the progenies from surely-selfed C0-1 was very poor, but that of the progenies crossed with commercial varieties of rapes was relatively high. In the progenies of surely-selfed C0-1, cross fertility with commercial varieties was higher than self fcrtility (Tables 6 & 11). Thus, the author believes that crossing between artificially synthesized and commercial Varieties of rapes is effective in stabilizing the behavior of chromosomes during the meiosis in PMCS and accordingly to improve seed fertility of the artificially synthesized rape. As to the number of chromosomes and seed fertility, many aneuploids were revealed in the progenies of surely-selfed C0-1. On the other hand, most progenies crossed with commercial varieties were cytologically stabilized having 2n=38 (Tables 7 & 12). It is considered that occurrence of these aneuploids may be caused by anomalous meiosis in artificially synthesized rapes and also by artificially controlled crossing. With regard to vegetative growth, the progenies of the artificially synthesized rape crossed with the commercial varieties was more vigorous, and had several advantages over the inbred line of C0-1. Therefore, the author considers that the result of this study points out one of the breeding methods in forage rape.
