Karyotypes and meiotic behavior of chromosomes in two male sterile strains of Brassica campestris L.

Abstract

Male sterility was examined in backcross families of the hybrid Diplotaxis muralis×B. campestris (murcytoplasm). Segregation of sterile and fertile plants did not fit to any of the Mendelian ratios. Since an extra chromosome is known to occur in sterile plants having a similar combination of mwr-cytoplasm and B. napus nucleus, the mitotic and meiotic chromosomes were analysed. Similarly, the chromosomes were examined in another male sterility system, in backcross families of B. napus x B. campestris (pol-cytoplasm). The normal chromosome number (2n = 20) was detected in all the sterile as well as the fertile plants. After improvements of the staining technique, all the chromosomes were identified in some cells. Ten bivalents were formed in meiosis and the segregation of chromosomes appeared to be normal. The visibility of satellites was examined at diakinesis. Variation among plants was observed but no correlation with male sterility was found.