Partial isolation of the genomic region linked with apomixis in Paspalum simplex

Abstract

Apomixis is a form of asexual reproduction through seed and has the potential to be applied, to great benefit, to agriculture. Understanding the genetic control of apomixis has proven to be a challenging task because the trait is mainly present in wild species and genetic mapping is often impaired by a block of recombination. A physical mapping approach has therefore been undertaken to unlock the genetic control of apomixis in Paspalum simplex Morong, a species with a relatively small genome and which exhibits a degree of genetic synteny with rice. In this paper, we report on the construction of a bacterial artificial chromosome library for Paspalum simplex with a coverage of approximately three genome equivalents and an average insert size of 94 kb. The BAC library was screened with 19 sequence characterized amplified region markers which were 100% linked to apomixis and a recombinant SCAR marker, all developed through a bulked segregant analysis strategy. A mini-sequencing procedure reported in the literature greatly aided the direct development of SCAR markers from amplified fragment length polymorphism bands. Several BAC clones linked to apomixis were identified and assembled into seven contigs and 18 singletons. Two of the BAC clones identified contained independently isolated markers. This is the first such report in an apomictic model that lacks recombination at the locus. We believe that extension of the contigs coupled to high-throughput sequencing will help the understanding of the genomic structure of the apomixis locus in P. simplex.