Histological and cytological study of ‘Mukaku Kishu'-derived female sterility in pummelo.

本研究以‘平洲’、‘向洲’、‘南黄’、‘Bul-7柚’及‘南黄’与Bu 1 -7柚杂交的BSYs实生苗为材料，研究了种子形成和染色体结构。无角吉鼠及其后代的无核性不能归因于胚囊异常和胚珠未受精.在所有的无籽品种和BSY实生苗中均观察到小粒种子，种子中心饱满，种皮不发达（暂称A型种子），其无核性应归属于A型种子.几乎A型种子的胚只发育到合子或原胚，胚乳不败育。部分无核品种的胚发育随年份的不同而发生变化，胚发育为心形胚或小子叶，表明胚发育受阻不是基因型所致.无核品种‘南方黄花’的胚在高温条件下发育成心形胚或小子叶，而有核品种‘平洲’经GA_3处理后形成A型种子。这些结果表明，植物生长调节剂和温度及/或某些胁迫会影响与A型种子形成相关的基因表达.在无核‘Mukaku Kishu’、‘Southern Yellow’和BSY 18中检测到与显性无核Fs基因连锁的DNA标记，在有核BSY 3、BSY 15和BSY 29中也检测到与显性无核Fs基因连锁的DNA标记。这说明BSY 3、BSY 15和BSY 29都含有抑制Fs基因表达的Is基因.根据PI（+）带型和GISH信号分析，Fs基因可能位于“Mukaku Kishu”的D1（绿色）型染色体或E型染色体上（E1和E5除外）; Is基因可能位于Bu 1 -7柚的C1（Red/Red）型、D1（Red）型或E型染色体上（E1除外）。

The results of this study in which seed formations and chromosome constructions were investigated using 'Hirakishu', 'Mukaku Kishu', 'Southern Yellow', Bul-7 pummelo and BSYs seedlings from Bu1-7 crossed by 'Southern Yellow' were summarized below.1. The seedlessness of 'Mukaku Kishu' and its progenies can not attributed to abnormal embryo sacs and unfertilized ovules.2. Small seeds with filling in center and undeveloped seed coat (call A type seed tentatively) were specifically observed in all seedless cultivars and BSY seedlings and the seedlessness should be attributed to A type seeds.3. The embryos in almost A type seeds only developed to the zygote or proembryo while the endospermes was not aborted. The development of embryo in some seedless cultivars varied by years and the embryos developed to hart-shape embryos or small cotyledons suggesting that arrested embryo development would not be resulted from genotypes of embryos.4. The embryos of seedless cultivar 'Southern Yellow' developed to hart-shape embryos or small cotyledons under high temperature condition and A type seeds were formed in seedy cultivar 'Hirakishu' by GA_3 treatments. The results suggested that plant growth regurators and temperature and/or some stresses would influence to the gene expressions concerned with A type seed formation.5. DNA marker linked to Fs gene which dominate seedlessness was detected in seedless 'Mukaku Kishu', 'Southern Yellow' and BSY18, and also detected in seedy BSY3, BSY15 and BSY29. This indicated that BSY3, BSY15 and BSY29 have Is gene which dominantly suppress the Fs gene expression.6. The results from chromosome constitution based on PI(+) band patterns and GISH signals suggested that Fs gene would locate on D1(Green) type chromosome or E type chromosome except E1 and E5 among 'Mukaku Kishu' chromosomes, and that Is gene would locate on C1(Red/Red) type, D1(Red) type or E type chromosome except E1 type among Bu1-7 pummelo chromosomes.