辐射诱发红桔少核的细胞遗传学

CYTOGENETIC STUDY ON THE IRRADIATION-INDUCED LOW SEEDINESS OF Citrus tangerina Hort.

研究表明,辐射诱发的少核红桔在有丝分裂前期和中期约有92.5％的细胞出现1—6对体细胞染色体联会。在对照株系中也能看到1—3对同源染色体的非交叉平行联会,仅占观察总数的31.4％,其余大多数细胞中的18条染色体则随机分散在核内;在花粉母细胞染色体行为的观察中,对照红桔终变期和中期Ⅰ约67.0％的细胞为正常的9对二价体,而辐射少核红桔却有67.3％畸变细胞类型,其中7Ⅱ+1Ⅳ构型的细胞占畸变细胞的53.4％;在后期和末期有落后染色体、染色体桥、重组核、三分体、异常四分体、五分体和九分体等畸变类型。红桔辐射少核与辐射导致染色体以易位杂合体为主的畸变有关。

Meiotic behavior of chromosomes in pollen mother cells and chromosome variation of somatic cells of Citrus tangerina Hort.irradiated with gamma rays were examined by means of imporoved smear method and wall degradation hypotonic method.The results obtained show that there are 2-6 pairs of somatic association (corsses or rods) in 92.5% of mitotic cells at the prophase and metaphase,wherese 85.0% of somatic cells of control strains are normal.In the PMCs,67.0% of cells at diakinesis and metaphase Ⅰ appear as 9Ⅱ configurations,but in the case of irradiated strains with low seediness the chromosome behavior shows great irregularity and complexity.The frequency of aberrations in PMC is 67.3%,including univale-nts,tetravalents,hexavalents and configurations of 7Ⅱ+1Ⅳ in aberratior cells are more than 53.4%.In later stages of meiosis various abnormalities of chromosome behavior including laggards,bridge,irregular chromosome distribution,formation of multiple plates and a few cases of formation of restitution nuclei occur.Various types of sporad groups,ranging from diads to enneads occur.The occurrence of 1-2 tetravalents and 2-6 univalents is the main cause of most gametic sterility and induces low seediness in irradiated strains.