Short description:

Cytoplasmic male sterility (CMS) is driven by rearrangements in the mitochondrial genome that result in plants being unable to produce fertile pollen. Usually, CMS is a binary system where the products of one or more nuclear genes (restorer genes) interfere with the causal mitochondrial proteins and reestablish fertility. CMS is widespread in the plant kingdom and has been described in more than 150 species including members of the Poaceae, Leguminosae, Umbelliferae, Brassicaceae, Chenopodiaceae, Solanaceae, and Liliaceae. Various cases of male sterility have been reported in the Rosaceae, as in Fragaria vesca, peach, Japanese apricot, almond, and pear. Of these, CMS has only been documented for peach, Japanese apricot and pear. CMS is an important model to analyze the interplay between organelle and nuclear genomes that has implications in the evolution of sex in plants, and is a key technological aspect in the development of F1 hybrid seed for many of the major herbaceous crops.

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Abstract taken from PubMed

Abstract:

Peach (Prunus persica) and almond (Prunus dulcis) are two sexually compatible species that produce fertile offspring. Almond, a highly polymorphic species, is a potential source of new genes for peach that has a strongly eroded gene pool. Here we describe the genetics of a male sterile phenotype that segregated in two almond (‘Texas’) × peach (‘Earlygold’) progenies: an F2 (T×E) and a backcross one (T1E) to the ‘Earlygold’ parent. High-density maps were developed using a 9k peach SNP chip and 135 simple-sequence repeats. Three highly syntenic and collinear maps were obtained: one for the F2 (T×E) and two for the backcross, T1E (for the hybrid) and E (for ‘Earlygold’). A major reduction of recombination was observed in the interspecific maps (T×E and T1E) compared to the intraspecific parent (E). The E map also had extensive monomorphic genomic regions suggesting the presence of large DNA fragments identical by descent. Our data for the male sterility character were consistent with the existence of cytoplasmic male sterility, where individuals having the almond cytoplasm required the almond allele in at least one of two independent restorer genes, Rf1 and Rf2, to be fertile. The restorer genes were located in a 3.4 Mbp fragment of linkage group 2 (Rf1) and 1.4 Mbp of linkage group 6 (Rf2). Both fragments contained several genes coding for pentatricopeptide proteins, demonstrated to be responsible for restoring fertility in other species. The implications of these results for using almond as a source of novel variability in peach are discussed.