小型四倍体西瓜低稔性胚胎发育研究

Study on Embryonic Development of Low-Fertility Tetraploid Mini-watermelon

以小型西瓜自交系049(2X)和049(4X)为材料,对二、四倍体花粉萌发、花粉管生长及受精后的胚胎发育进行观察分析。分析结果表明,二倍体西瓜花粉萌发率较高,达96.3%,花粉管生长整齐一致,生长速度快,授粉后9 h进入子房;四倍体花粉粒形态异常的较多,花粉萌发率较低,仅为63.7%,花粉管生长易扭曲、折叠、盘绕,生长速度慢,授粉后12 h才进入子房。在胚胎发育过程中,小型二倍体西瓜胚胎发育速度快,胚体退化现象少;四倍体西瓜胚胎发育速度慢,从原胚到鱼雷胚期间容易出现因胚乳游离核或胚乳细胞解体而导致胚败育。可见四倍体西瓜正常花粉减少、花粉管生长异常及胚体退化是造成四倍体低稔性的重要原因。

The pollen germination,pollen tube growth and embryo development of mini-watermelon 049（2X,4X） were studied.The results showed that diploid mini-watermelon possessed higher pollen germination rate of 96.3%,and its pollen tube grew rapidly and reached the ovary nine hours after pollination.The abnormal pollens increased and the pollen germination rate was relatively low（only 63.7%） in tetraploid mini-watermelon.During the development of pollen tube in tetraploid mini-watermelon,the pollen tube were easily twisted,folded and coiled,and grew relatively slowly and reached the ovary twelve hours after pollination.The embryos of diploid mini-watermelon developed faster.At the stage of developing from ball embryo to torpedo embryo,more embryos were degenerated and sterile in tetraploid mini-watermelon because of the disintegration of the free nuclei or endosperm cells,indicating main reasons for the low fertility of tetraploid mini-watermelon were the decrease of normal pollens,abnormal growth of pollen tube and degeneration of embryos.