High-density mapping suggests cytoplasmic male sterility with two restorer genes in almond × peach progenies

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.

Exploring sources of resistance to brown rot in an interspecific almond × peach population

“…A previously described interspecific backcross one (BC1) population of 185 individuals derived from a hybrid plant (‘MB 1.37’) from the cross between ‘Texas’ (almond) and ‘Earlygold’ (peach), backcrossed to ‘Earlygold’, for which a genetic map exists, was used in this research . In this BC1 population (named T1E) all individuals are peach type .…”

“…For the QTL analysis, a highly saturated map of the T1E population described by Donoso et al was used. The map used was based on the subset of 2032 markers heterozygous in the ‘Texas’ × ‘Earlygold’ hybrid parent and was constructed using the MAPMAKER 3.0 and Kosambi's mapping function.…”

“…A previously described interspecific backcross one (BC1) population of 185 individuals derived from a hybrid plant ('MB 1.37') from the cross between 'Texas' (almond) and 'Earlygold' (peach), backcrossed to 'Earlygold', for which a genetic map exists, was used in this research. 25 In this BC1 population (named T1E) all individuals are peach type. 23 Fruit that had not received any synthetic fungicide applications in the field or postharvest, and that were free of visible wounds and rot, were obtained from the Experimental Station of Lleida in Gimenells (Catalonia, Spain) at commercial maturity.…”

“…For the QTL analysis, a highly saturated map of the T1E population described by Donoso et al 25 was used. The map used wileyonlinelibrary.com/jsfa Table 1.…”

Transposons played a major role in the diversification between the closely related almond (Prunus dulcis) and peach (P. persica) genomes: Results from the almond genome sequence

“…Nanopore reads were mapped to the assembly with NGM-LRv0.2.6 (Sedlazeck et al 2018), the assembly was broken at regions of zero coverage and then re-scaffolded with SSPACE-LongRead v1.1 (Boetzer and Pirovano 2014). A second round of corrections was made utilizing collinearity with the (Texas almond x Earlygold peach; TxE) genetic F2 and BC1 (to Earlygold) maps (Donoso et al 2015) as the main criterion, with break points guided by synteny with the peach genome and coverage of nanopore reads. Peach transcripts (annotation Pp2.01a) were mapped to the almond assembly with GMAP v2014-12-23 (Wu and Watanabe 2005).…”