同源四倍体桑品种陕桑402-1的花粉母细胞减数分裂和小孢子形成过程观察

Observation on Meiosis of Pollen Mother Cells and Formation of Microspores in Autotetraploid Mulberry Variety Shansang 402-1

进行有性生殖的开花植物在形成染色体减半的生殖细胞过程中发生的减数分裂,与花粉的育性有很大关系。多倍体桑树具有生长旺盛、叶片肥大、叶质优良和抗逆性较强等特点,但是花粉的育性较低。从细胞学水平观察同源四倍体桑品种陕桑402-1花粉母细胞(PMCs)减数分裂以及小孢子的形成过程,分析多倍体桑树花粉育性降低的原因。观察发现PMCs减数分裂过程与花蕾大小有一定的相关性,当花蕾直径在0.71~1.54 mm之间时,PMCs处于减数分裂时期。在减数分裂过程中观察到了多价体、落后染色体和分裂不同步等异常情况:处于中期Ⅰ的染色体构型以二价体和四价体为主;四分体时期则出现了二分体、三分体、含微核的异常四分体以及多分体现象。观察小孢子发育分为4个时期,包括四分体时期、单核期、单核靠边期、双核期。初步推测陕桑402-1的PMCs在减数分裂过程出现上述异常情况,是导致其花粉育性降低的细胞学因素。

Meiosis is closely related to pollen fertility of flowering plants. Polyploid mulberry varieties have the characteristics of strong growth vigor,large and thick leaves,excellent leaf quality and high resistance. However,their pollen fertility is relatively low. In order to explore reasons of low pollen fertility in polyploidy mulberry,we observed the meiosis process of pollen mother cells（ PMCs） and the formation process of microspores in autotetraploid mulberry variety Shansang402-1 at cytogenetic level. The results showed that the meiosis process of PMCs is related to bud size. When the bud diameter was between 0. 71 and 1. 54 mm,PMCs were in the meiosis period. During meiosis process,multivalents and lagging chromosomes were observed. Moreover,chromosome segregation was not synchronous： in metaphaseⅠ,chromosomes were mainly composed of bivalents and quadrivalents; at tetrad stage,dyad,triad,tetrad with micronuclei and polyad were observed. It was observed that the microspore development was divided into four periods,including tetrad stage,uninucleate stage,late uninucleate stage,and binucleate stage. The abnormal status observed in meiosis of PMCs may be the cytological factors leading to low pollen fertility of the autotetraploid mulberry Shansang 402-1.