Marker-assisted screening of breeding populations of an apomictic grass Cenchrus ciliaris L. segregating for the mode of reproduction

Abstract Cenchrus ciliaris L. is an apomictic forage grass grown in pastures and rangelands of the semi-arid tropics. It reproduces predominantly through apomixis; rarely, obligate sexual plants have also been reported. Absence of sexual reproduction limits the possibility of genetic improvement through hybridization. This study reports on hybridization of an obligate sexual, self-incompatible buffelgrass with pollen from apomictic plants towards development of an F2 population segregating for mode of reproduction and use of sequence characterized amplified region (SCAR) markers for screening the population. The segregation ratio of 3:1 (facultative: apomictic) was observed in the F1 generation, whereas it was 1:2:1 (apomictic: facultative: sexual) in the F2 generation. A number of obligate sexual F2 progenies with desirable agronomic traits were obtained. The SCAR markers were able to screen out apomictic plants from sexual ones, but failed to discriminate between facultative and sexual. Marker-assisted screening could be useful for introgression of desirable trait(s) in the apomictic genotype through hybridization.

摘要 非洲狼尾草（Cenchrus ciliaris L.）是一种无融合生殖（apomictic）饲草，广泛栽培于半干旱热带地区的牧场与天然牧地中。该物种主要以无融合生殖方式繁衍，仅在极少数案例中报道过专性有性生殖植株。有性生殖的缺失限制了通过杂交开展遗传改良的可行性。本研究以专性有性、自交不亲和的非洲狼尾草为材料，以无融合生殖植株的花粉为父本开展杂交实验，旨在构建繁殖方式发生分离的F₂群体，并利用序列特征化扩增区域（sequence characterized amplified region, SCAR）标记对该群体进行筛选。F₁代的分离比例为3:1（兼性生殖:无融合生殖），而F₂代的分离比例为1:2:1（无融合生殖:兼性生殖:有性生殖）。本研究获得了一批具备优良农艺性状的专性有性F₂子代。SCAR标记可有效区分无融合生殖与有性生殖植株，但无法鉴别兼性生殖与有性生殖个体。标记辅助筛选技术可用于通过杂交将优良性状渐渗至无融合生殖基因型中。