Abstract

Cytoplasmic male sterility (CMS) results from incompatibility between nuclear and cytoplasmic genomes, and is characterized by the inability to produce viable pollen. The restoration of male fertility generally involves the introgression of nuclear genes, termed restorers of fertility (Rf). CMS has been widely used for hybrid seed production in many crops but not in wheat, partly owing to the complex genetics of fertility restoration. In this study, an acrocentric chromosome that restores pollen fertility of CMS wheat in Hordeum chilense cytoplasm (msH1 system) is studied. The results show that this chromosome, of H. chilense origin and named H(ch)ac, originated from a complex reorganization of the short arm of chromosomes 1H(ch) (1H(ch)S) and 6H(ch) (6H(ch)S). Diversity arrays technology (DArT) markers and cytological analysis indicate that H(ch)ac is a kind of `zebra-like' chromosome composed of chromosome 1H(ch)S and alternate fragments of interstitial and distal regions of chromosome 6H(ch)S. PCR-based markers together with FISH, GISH, and meiotic pairing analysis support this result. A restorer of fertility gene, named Rf6H(ch)S, has been identified on the short arm of chromosome 6H(ch)S. Moreover, restoration by the addition of chromosome 1H(ch)S has been observed at a very low frequency and under certain environmental conditions. Therefore, the results indicate the presence of two Rf genes on the acrocentric chromosome: Rf6H(ch)S and Rf1H(ch)S, the restoration potential of Rf6H(ch)S being greater. The stable and high restoration of pollen fertility in the msH1 system is therefore the result of the interaction between these two restorer genes.

Highlights

  • Global demand and consumption of agricultural crops for food, animal feed, and fuel are increasing at a rapid rate

  • Alloplasmic and restored lines were hybridized with an array composed of a total of 4941 Diversity arrays technology (DArT) clones, most of them derived from H. chilense and hexaploid wheat probes

  • Restored lines T528 (42+ac′′) and T700 (42+ac′) gave positive signals in the array with markers assigned to chromosomes 1HchS and 6HchS exclusively, which indicated that the acrocentric chromosome Hchac was formed by only these two chromosome arms of H. chilense

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Summary

Introduction

Global demand and consumption of agricultural crops for food, animal feed, and fuel are increasing at a rapid rate. Fertility restoration of the CMS phenotype was associated with the addition of the short arm of chromosome 6Hch of H. chilense (Martín et al, 2008a). Diversityarrays.com) and hybridized to the same resulting composite array which was used to fingerprint tritordeum and wheat-H. chilense chromosome addition lines (Castillo et al, 2013).

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