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从水稻双胚苗中提高不定胚的发生频率是研究利用无融合生殖固定Ｆ１代杂种优势的主要途径之一。通过特殊的选育方法，已将原有双胚苗品系的双苗率由３０％提高到６０％左右。由于不定胚与双苗的发生率有着一定的内在联系，随着双苗率的提高，内含不定胚的频率也有相应提高的趋势。又据细胞学观察，认为不定胚发生在远离珠孔端的部位，故在种子中部的萌发苗可能是不定胚产生的种子形态学特征。１９８９年，我们采用特定苗位为标记的筛选方法，选取种子正中部萌发苗并结合对其它非正中苗的人工切除，使水稻的不定胚频率由原来的２．６—５．１％提高到２１．２％。水稻不定胚频率的大幅度提高，为无融合生殖在杂交水稻育种中的研究应用开拓了诱人的前景。
Increasing the frequency of adventitious embryos from rice double embryo seedlings is one of the main ways to study the heterosis of F1 generation by apomixis fixation. Through special breeding methods, the double seedling rate of the original double embryo seedling strain has been increased from 30% to about 60%. Because of the inherent relationship between adventitious embryos and the incidence of double vaccine, with the increase of vaccination rate, the frequency of adventitious embryos also increased accordingly. According to cytological observation, it is considered that adventitious embryos occur at the part far away from the end of the micropylar. Therefore, the germination seedlings in the middle part of the seed may be morphological characteristics of the seed produced by adventitious embryos. In 1989, we selected the specific seedling as a marker screening method, select the seed germination in the middle of the seed and combined with other non-positive seedlings of artificial excision, the adventitious embryos frequency increased from 2.6-5.1% 21.2%. The adventitious frequency of rice greatly increased, which opened up an attractive prospect for the research and application of apomixis in hybrid rice breeding.