High-density mapping suggests cytoplasmic male sterility with two restorer genes in almond × peach progenies.
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.
IRTA, Centre de Recerca en Agrigenòmica CSIC-IRTA-UAB-UB; Campus UAB, Bellaterra (Cerdanyola del Vallès) , 08193 Barcelona, Spain.
José Manuel
JM
Donoso
IRTA, Centre de Recerca en Agrigenòmica CSIC-IRTA-UAB-UB; Campus UAB, Bellaterra (Cerdanyola del Vallès) , 08193 Barcelona, Spain.
Iban
I
Eduardo
IRTA, Centre de Recerca en Agrigenòmica CSIC-IRTA-UAB-UB; Campus UAB, Bellaterra (Cerdanyola del Vallès) , 08193 Barcelona, Spain.
Roger
R
Picañol
IRTA. Centre de Mas de Bover. Crta. De Reus - El Morell Km 3.8. 43120 Constantί , Tarragona, Spain.
Ignasi
I
Batlle
IRTA, Centre de Recerca en Agrigenòmica CSIC-IRTA-UAB-UB; Campus UAB, Bellaterra (Cerdanyola del Vallès) , 08193 Barcelona, Spain.
Werner
W
Howad
IRTA, Centre de Recerca en Agrigenòmica CSIC-IRTA-UAB-UB; Campus UAB, Bellaterra (Cerdanyola del Vallès) , 08193 Barcelona, Spain.
María José
MJ
Aranzana
IRTA, Centre de Recerca en Agrigenòmica CSIC-IRTA-UAB-UB; Campus UAB, Bellaterra (Cerdanyola del Vallès) , 08193 Barcelona, Spain.
Pere
P
Arús