墨兰兔耳兰杂交后代2n雄配子发生及其细胞学机制

2n male gametogenesis and its cytological mechanism in hybrids of Cymbidium sinense×C.lancifolium

为更有效开展国兰多倍体育种,采用显微观测技术对‘小香墨兰’、兔耳兰及其31份杂交后代2n雄配子发生及其细胞学机制进行了研究。结果显示:‘小香墨兰’兔耳兰30份杂交后代2n雄配子发生率变幅为0%9.36%,3 a平均发生率为2.28%,显著高于母本(0.19%)和父本(0.22%),获得2n雄配子平均发生率大于3%的资源8份。不同杂交后代2n雄配子发生率差异显著,多数后代不同年份间2n雄配子发生率差异显著,说明杂种后代雄配子发生既受遗传控制也受环境条件影响。杂种2n雄配子通过二分体和三分体方式产生,但不同后代主要发生途径不完全相同。二分体方式形成2n雄配子主要是由于小孢子母细胞减数分裂不同步导致一些小孢子母细胞减数分裂Ⅰ不分裂、减数分裂Ⅱ正常分裂所致,而三分体方式形成则是由于减数分裂Ⅱ纺锤体异常定向形成三极纺锤体所致。

Microscopic observation was used to study 2n male gametogenesis and its cytological mechanism in Cymbidium sinense‘Xiaoxiang’,C.lancifolium and its thirty-one hybrids to more effectively develop the breeding of polyploids in Chinese Cymbidium.The results showed the occurrence frequency of unreduced male gamete of thirty hybrids ranged from 0%to 9.36%.The average occurrence frequency of consecutive three years was 2.28%,significantly higher that of both male parent(0.22%)and female parent(0.19%).Eight hybrids with average occurrence frequency of more than 3%were obtained.There were significant differences in the average occurrence frequency of 2n male gamete among hybrids.The average occurrence frequency of 2n male gamete in most hybrids was significantly different among different years,indicating that the occurrence frequency of 2n male gamete was not only controlled by genetic factor but also significantly affected by environmental condition.The unreduced male gamete in the interspecific hybrids was produced with both dyad and triad.However,the main way of producing unreduced male gamete was not completely the same in hybrids.The formation of dyads was mainly due to the asynchronous meiotic division of microspore mother cells,resulting in some microspore mother cells not dividing in meiosisⅠand normal division in meiosisⅡ,while the formation of triad was caused by the abnormal orientation of the meioticⅡspindle to form a tripolar spindle in the interspecific hybrids.