Nielen Stephan, Almeida Lucas M, Carneiro Vera T C, Araujo Ana Claudia G
Embrapa Genetic Resources and Biotechnology, Parque Estação Biológica (PqEB), Final W5 Norte, P.O.Box 02354, Brasília, DF, 70770-900, Brazil.
Sex Plant Reprod. 2010 Mar;23(1):45-51. doi: 10.1007/s00497-009-0124-1. Epub 2009 Dec 15.
Brachiaria (Trin.) Griseb belongs to the family Poaceae, and within the genus, apomixis or sexuality is present in different accessions of the same species. The majority of Brachiaria species are polyploid and apomictic, making strategies for crop improvement by breeding very intricate. In spite of the high frequency of apomictic polyploids, the relationship of polyploidy and hybridization with apomixis in Brachiaria is still unclear. Further analysis requires detailed knowledge regarding the genomic composition of the polyploids. The present work introduces the use of fluorescent in situ hybridization (FISH) into cytogenetic analysis of Brachiaria. Physical mapping of heterologous rDNA sequences, associated with conventional karyotyping of the B. brizantha diploid sexual (BRA 002747) and the tetraploid apomictic (BRA000591) accessions, provided evidence of the latter being of allopolyploid origin. Based on our results and on previous knowledge on apomixis in B. brizantha, we suggest that the origin of apomixis was probably a consequence of hybridization.
臂形草属（Trin.）Griseb属于禾本科，在该属内，同一物种的不同种质存在无融合生殖或有性生殖现象。大多数臂形草物种是多倍体且为无融合生殖，这使得通过育种改良作物的策略非常复杂。尽管无融合生殖多倍体的频率很高，但臂形草中多倍体和杂交与无融合生殖的关系仍不清楚。进一步的分析需要有关多倍体基因组组成的详细知识。本研究将荧光原位杂交（FISH）引入臂形草的细胞遗传学分析。对异源rDNA序列进行物理图谱分析，并结合二倍体有性生殖的巴西臂形草（BRA 002747）和四倍体无融合生殖的巴西臂形草（BRA000591）种质的常规核型分析，证明了后者具有异源多倍体起源。基于我们的研究结果以及之前关于巴西臂形草无融合生殖的知识，我们认为无融合生殖的起源可能是杂交的结果。
