四川8个枇杷品种染色体变异研究

Chromosome Variation in 8 Loquat Varieties in Sichuan Province

对四川８个枇杷品种：早红１号、早红３号、金丰、龙泉８０－１、龙泉１号、大五星、黄肉及早白沙的核型进行了分析。其染色体数目均为２ｎ＝２ｘ＝３４。核型可分为两大类：第１类为前７个品种，核型由中部着丝粒染色体（ｍ）和近中部着丝粒染色体（ｓｍ）组成，最长染色体与最短染色体比值均小于２，属２Ａ核型，其核型公式可表示为２ｎ＝２ｘ＝３４＝（１４～２０）ｍ＋（１４～２０）ｓｍ，表明它们具有极其近缘的关系；第２类为早白沙，核型组成除具上述两种染色体类型外，还包括两条近端部着丝粒染色体（ｓｔ），属３Ｂ核型，核型公式为２ｎ＝２ｘ＝３４＝１３ｍ＋１９ｓｍ＋２ｓｔ，在第１、２对染色体中分别存在１条近端部着丝粒染色体（ｓｔ）和１条近中部着丝粒染色体（ｓｍ），显示出该品种染色体的高度杂合性。两大类核型与枇杷品种依据果肉颜色分类基本吻合。还讨论了染色体结构变异的遗传机制。

The karyotypes of 8 loquat varietiesEriobotrya japonica(Thunb)Lindl.in Sichuan i.e .Zaohong No.1 ,Zaohong No.3 ,Jinfeng,Longquan 80-1,Longquan No.1 ,Dawuxing,Huangrou and Zaobaisha were studied by the hypotonic degradation method.According to karyotype types,8 loquat varieties can be divided into two groups.The first group,including the former 7 varieties of 8,consists of only two types of chromosome metacentric(m)and submetacentric chromosome(sm),which belong to2Akaryotype with the ratio of the longest to the shortest chromosome less than 2,and their karyotype formula can be summed as 2 n=2 x=34=(14-20)m+(14-20)sm.The second group only involves a variety Zaobaisha with white pulp of fruit,which contains two subtelocentric chromosomes(st)besides the two types of chromosomes mentioned above,belonging to3Bkaryotype with 2 n=2 x=34=13 m+19 sm+2 st.The first and second pairs of chromosomes in Zaobaisha consist of a subtelocentric chromosome(st)and a submetacentric chromosome(sm),respectively,which show a high heterozygositical karyotype.It suggets that the second karyotype would be evolved from the first one.Two group karyotypes conforms to the result of loquat classification according to their colour of pulp of fruit.Finally,the cytogenetic mechanism of chromosomal structure variation is discussed.