Molecular identification of the cytoplasmic male sterile source from Dongxiang wild rice (Oryza rufipogon Griff.)

The use of cytoplasm male sterility (CMS) is crucial for three-line hybrid seed production. Two types of CMS have been discovered from Dongxiang wild rice, namely the wild abortion type CMS (CMS-WA) and the Dongxiang wild type CMS (CMS-DW). In this study, we show the molecular identification of the two types of CMS in Dongxiang wild rice. WA352, which conferred CMS-WA, was not detected in Dongxiang wild rice, implying Dongxiang wild rice does not carry the CMS-WA source. Further analysis of WA352 in DY1A, a CMS-DW line, by PCR amplification and sequencing, revealed two insertion-deletion polymorphisms occurred in CMS-DW compared to WA352 of CMS-WA. It was reported that WA352 was comprised of an unknown origin sequence and partial sequences of three open reading frames (ORFs), orf284, orf224 and orf288. The 42-bp insertion was located between the two segments of orf224 and orf288, which created a new chimeric ORF, orf216. This new ORF was also detected in CMS-HL. Based on the 9-bp deletion in orf284, a specific mitochondrial marker of DW-M1 was developed, which could be used to specifically distinguish the DW-type source. Moreover, semi-quantitative RT-PCR analysis preliminarily suggested that both orf216 and orf284 could be considered as candidates for CMS-DW. These findings present a preliminary understanding of CMS-DW at the molecular level.