Fruit characteristics and seed anatomy of 'Majia' pomelo pollinated with cobalt-60 gamma-ray-irradiated pollen
Fruit characteristics and seed anatomy of 'Majia' pomelo pollinated with cobalt-60 gamma-ray-irradiated pollen
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钴60γ射线辐照花粉授粉‘马家’柚子果实特性及种子解剖
DOI：
10.1016/j.scienta.2020.109335
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发表时间：
2020
影响因子：
4.3
通讯作者：
Yong Liu
中科院分区：
文献类型：
--
作者：
Li Yang;Dechun Liu;Wei Hu;Yongqiang Chun;Juanjuan Zhang;Yong Liu
马甲柚（Citrus maxima(Burm.) Merr.，芸香科)是中国江西省的特色地方品种，以其风味好、番茄红素含量丰富而闻名。然而，每个“马家”柚子通常含有大约 120 至 200 颗大种子。为了获得无籽‘马家’柚子果实，我们采用酸柚（当地常用授粉品种）的花粉，经1000Gy钴60伽玛射线照射后，对‘马家’柚进行授粉。该杂交产生的无籽果实在果实重量、果实直径、果皮厚度、总可溶性固形物 (TSS) 含量、维生素 C (Vc) 含量、糖含量和可滴定酸度方面表现出与具有可育种子的果实相似的特征。有趣的是，在体外发芽试验中，花粉活力并未受到辐射的影响，并且受辐射的花粉管沿着花柱管正常生长成胚珠。无核果肉中 IAA、GA3 和 ZR 的浓度高于有核果，且 (IAA+GA3+ZR)/ABA 比值也较高；然而，这两种水果的种子中的激素浓度和比例与果肉中的相反。这些结果可能是辐照花粉受精的果实能够保持果实生长和果实品质的重要原因。石蜡切片显示，授粉后两周，两种花粉处理下的胚乳核均沿胚囊壁延伸；授粉后7周，未辐照花粉受精的胚囊中部分胚乳已进入细胞化阶段，但辐照花粉受精的大部分胚珠出现胚乳退化和皱缩。胚乳通过提供储存在细胞中的营养物质，在胚胎生长中发挥着非常重要的作用。我们的研究表明，用辐照花粉授粉的发育种子中的早期胚乳退化可能是种子败育的关键原因。
The 'Majia' pomelo (Citrus maxima(Burm.) Merr., Rutaceae) is a distinctive local cultivar of Jiangxi province, China, that is famous for its good flavour and abundant lycopene content; however, each 'Majia' pomelo fruit usually contains approximately 120–200 large seeds. To obtain seedless 'Majia' pomelo fruit, we used pollen from sour pomelo (a local variety generally used for pollination) irradiated with 1000 Gy cobalt-60 gamma rays to pollinate 'Majia' pomelo. This cross produced seedless fruit that displayed similar features to those of fruit with fertile seeds in terms of fruit weight, fruit diameter, peel thickness, total soluble solid (TSS) content, vitamin C (Vc) content, sugar content and titratable acidity. Interestingly, pollen viability was not affected by irradiation in an in-vitro germination test and the irradiated pollen tubes grew normally along the stylar canals into ovules. The pulp of the seedless fruit contained higher concentrations of IAA, GA3, and ZR and a higher (IAA+GA3+ZR)/ABA ratio than that of seeded fruit; however, the hormone concentrations and ratios in the seeds of these two kinds of fruit were opposite to those in the pulp. These results may be important reasons that the fruit fertilized with irradiated pollen could maintain fruit growth and fruit quality. Paraffin sectioning showed that, the endosperm nuclei extended along the wall of the embryo sac under both pollen treatments at two weeks after pollination; at seven weeks after pollination, some of the endosperm had entered the cellularization stage in the embryo sacs fertilized with nonirradiated pollen, but endosperm degeneration and shrinkage were observed in most ovules fertilized with irradiated pollen. The endosperm plays a very important role in embryo growth by providing nutrients stored in its cells. Our study demonstrates that early endosperm degeneration in developing seeds pollinated with irradiated pollen may be a crucial reason for seed abortion.