CYTOLOGICAL STUDIES ON RYE PLANTS WITH SEVEN AND EIGHT ACCESSORY CHROMOSOMES

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Abstract
The cytological behavior of accessory chromosomes in the native rye of Japan, JNK, with 7 and 8 accessories was observed in meiosis. Both plants had a large number of accessory chromosomes but the accessory chromosomes paired very well with each other and formed many radial multivalents. In the radial multivalents, 2 types were distinguished one symmetrical and the other asymmetrical. The disjunction of accessory chromosomes at anaphase I was not unusual, being determined by the type of metaphase I configuration. In most of cells, 3-4 and 5-2 distributions were observed in the 7 accessory plant; and 4-4 and 5-3 in the 8 accessory plant. Cells with 1 or 2 laggard accessory chromosomes were often observed, but the number of micro-nuclei in tetrads was very few, suggesting that the meiotic elimination of accessory chromosomes is very low. The numerical limit of accessory chromosomes contained per plant might be essentially related to the extent of heterochromatic segment.