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

本研究以‘平久’、‘木瓜’、‘南黄’、‘Bul-7’、‘BSYS’为材料，以BU1-7为材料，与‘南黄’杂交，对其种子形成和染色体结构进行了研究，结果如下：‘Mukaku Kishu’及其后代的无核不能归因于胚囊异常和未受精的卵子。在所有无核品种和BSY苗木中，都能观察到中心填满、种皮不发达的小粒种子(暂称A型种子)，其无核性应归因于A型种子。几乎A型种子的胚仅发育为合子或原胚，胚乳不败育。部分无核品种的胚胎发育因年份而异，胚胎发育成Hart形胚胎或小子叶，表明胚胎发育受阻不是由胚胎的基因型引起的。无核品种‘南方黄’的胚胎在高温条件下发育成Hart形胚胎或小子叶，而多粒品种‘Hirakishu’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、温度和/或某些胁迫会影响与A型种子形成相关的基因表达。无核品种‘Mukaku Kishu’、‘南方黄’、BSY18和多籽粒品种BSY3、BSY15、BSY29均检测到与F基因连锁的DNA标记。这说明BSY3、BSY15和BSY29都含有以抑制FS基因表达为主的IS基因。基于PI(+)带型和GISH信号的染色体组成结果表明，在‘Mukaku Kishu’染色体上，除E1和E5外，FS基因可能位于D_1(Green)型或E_型染色体上；在BU1-7柚染色体中，除E_1型外，FS基因可能位于C_1(红/红)型、D_1(红)型或E_型染色体上。

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.