Zhang Yuhuan, Wu Hairong, Hörandl Elvira, de Oliveira Franca Rafael, Wang LiXin, Hao Jianhua
School of Biology and Food Engineering, Changshu Institute of Technology, Nansanhuanlu 99, Changshu 215500, Jiangsu Province, China.
College of Life Sciences, Northwest Normal University, No. 967, Anningxi Road, Lanzhou City 730070, Gansu Province, China.
AoB Plants. 2021 Jan 29;13(2):plab007. doi: 10.1093/aobpla/plab007. eCollection 2021 Apr.
Understanding the reproductive mechanisms of invasive alien species can lay the foundation for effective control measures. is a triploid neotropical Asteraceae species that is invasive in China and other countries. However, few studies have focused on its reproductive biology. In this study, flow cytometric seed screening (FCSS) was used to identify and confirm the reproductive mode of the species. The development of ovules, anthers, and mega- and microgametophytes was observed using a clearing method and differential interference contrast microscopy. Pollen viability was measured using the Benzidine test and Alexander's stain. Pollen morphology was observed via fluorescence microscopy after sectioning the disk florets and staining with water-soluble aniline blue or 4'6-diamidino-2-phenylindole nuclei dyes. Controlled pollination experiments were conducted on four populations in China to examine the breeding system and to confirm autonomous apomixis. The reproductive mode was found to be autonomous apomixis without pseudogamy, according to FCSS. Megaspore mother cells developed directly into eight-nucleate megagametophytes without meiosis, conforming to -type diplospory. The unreduced egg cells developed into embryos through parthenogenesis, while the endosperm was formed by the fusion of two unreduced polar nuclei. Pollen viability was very low (0.82 ± 0.57 % and 0.36 ± 0.44 %) as measured by the Benzidine test and Alexander's stain, respectively. The majority of the pollen grains were empty and had neither cytoplasm nor nuclei. The seed set was >90 % for all treatments of open pollination, bagging and emasculated capitula. Mature cypselae developed in capitula that were emasculated before flowering, which confirmed that the breeding system of was autonomous apomixis. The present study is the first report of autonomous apomixis in in China. -type autonomous apomixis in greatly increases the probability of successful colonisation and dispersal of into new areas, which likely contributes to its high invasion potential. Effective control measures should be implemented to prevent autonomous (pollen-independent) seed production.
了解外来入侵物种的繁殖机制可为有效的控制措施奠定基础。[物种名称]是一种三倍体新热带菊科物种，在中国和其他国家具有入侵性。然而，很少有研究关注其繁殖生物学。在本研究中，采用流式细胞术种子筛选（FCSS）来鉴定和确认该物种的繁殖模式。使用透明法和微分干涉对比显微镜观察胚珠、花药以及大、小配子体的发育。使用联苯胺试验和亚历山大染色法测定花粉活力。在对盘状小花进行切片并用水溶性苯胺蓝或4',6-二脒基-2-苯基吲哚核染料染色后，通过荧光显微镜观察花粉形态。在中国的四个种群上进行了控制授粉实验，以研究其繁育系统并确认无融合生殖。根据FCSS结果，发现其繁殖模式为无配子生殖的自主无融合生殖。大孢子母细胞直接发育成八核大配子体，无减数分裂，符合[具体类型]二倍体孢子生殖。未减数的卵细胞通过孤雌生殖发育成胚，而胚乳由两个未减数的极核融合形成。通过联苯胺试验和亚历山大染色法测定的花粉活力分别非常低（0.82±0.57%和0.36±0.44%）。大多数花粉粒是空的，既没有细胞质也没有细胞核。所有开放授粉、套袋和去雄头状花序处理的结实率均>90%。在开花前进行去雄的头状花序中发育出成熟的瘦果，这证实了[物种名称]的繁育系统是自主无融合生殖。本研究是中国关于[物种名称]自主无融合生殖的首次报道。[物种名称]的[具体类型]自主无融合生殖极大地增加了其成功定殖和扩散到新区域的可能性，这可能是其具有高入侵潜力的原因。应实施有效的控制措施以防止自主（不依赖花粉）种子生产。
