CYTOGENETICS AND MORPHOLOGY OF THE PENTAPLOID HYBRID BETWEEN BRASSICA-NAPUS AND ORYCHOPHRAGMUS-VIOLACEUS AND ITS PROGENY

A pentaploid hybrid plant (2n = 50, AACCO) between Brassica napus (AAC C) and Orychophragmus violaceus (OO) showed matroclinous morphology an d some patroclinous characters. Cloned progenies were mixoploid, consi sting of various cells with 38-53 chromosomes, half of the cells with 50 chromosomes. The 50 chromosomes were mainly paired as 25 bivalents and segregated as 25:25 or 22:28; many other segregations were observe d in some cells. Progenies produced by selling had 38-47 chromosomes. Plants with 38 chromosomes were cytologically stable; in all other pla nts the chromosome number of individual cells varied between the genot ype-specific maximum number and 38, indicating loss of chromosomes dur ing mitosis. The mixoploid plants with 44 chromosomes mainly produced two kinds of mixoploid progenies with 44 and 41 chromosomes, respectiv ely. All plants with 2n = 38 had the same morphology as the parental B . napus and were normal in fertility. These chromosome pairings and se gregations in the pentaploid and its progeny support the hypothesis th at O. violaceus is a natural polyploid species with a basic chromosome number of 3.