Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias, Ctra. Moncada-Náquera km 4·5, Moncada, Valencia, Spain.
Ann Bot. 2010 Oct;106(4):533-45. doi: 10.1093/aob/mcq148. Epub 2010 Jul 30.
Adventitious embryony from nucellar cells is the mechanism leading to apomixis in Citrus sp. However, singular cases of polyembryony have been reported in non-apomictic genotypes as a consequence of 2x × 4x hybridizations and in vitro culture of isolated nucelli. The origin of the plants arising from the aforementioned processes remains unclear.
The genetic structure (ploidy and allelic constitution with microsatellite markers) of plants obtained from polyembryonic seeds arising from 2x × 4x sexual hybridizations and those regenerated from nucellus culture in vitro was systematically analysed in different non-apomictic citrus genotypes. Histological studies were also conducted to try to identify the initiation process underlying polyembryony.
All plants obtained from the same undeveloped seed in 2x × 4x hybridizations resulted from cleavage of the original zygotic embryo. Also, the plants obtained from in vitro nucellus culture were recovered by somatic embryogenesis from cells that shared the same genotype as the zygotic embryos of the same seed.
It appears that in non-apomictic citrus genotypes, proembryos or embryogenic cells are formed by cleavage of the zygotic embryos and that the development of these adventitious embryos, normally hampered, can take place in vivo or in vitro as a result of two different mechanisms that prevent the dominance of the initial zygotic embryo.
不定胚起源于珠心细胞，这是导致柑橘属植物无融合生殖的机制。然而，在非无融合生殖的基因型中，也有报道称，由于 2x×4x 杂交和离体珠心培养，会产生多胚现象。这些多胚起源的植物的来源尚不清楚。
本研究系统分析了来自 2x×4x 有性杂交多胚种子和离体培养珠心再生的不同非无融合生殖柑橘基因型植物的遗传结构（倍性和微卫星标记的等位基因组成）。还进行了组织学研究，试图确定多胚发生的起始过程。
来自 2x×4x 杂交中同一未发育种子的所有植物都来源于原始合子胚的分裂。此外，来自离体珠心培养的植物是通过体细胞胚胎发生从与同一种子的合子胚胎具有相同基因型的细胞中再生的。
在非无融合生殖的柑橘基因型中，原胚或胚性细胞似乎是通过合子胚的分裂形成的，这些不定胚的发育可以通过两种不同的机制在体内或体外进行，这两种机制阻止了初始合子胚的优势。
