Construction of a Linkage Map and Identification of Resistance Gene Analog Markers for Root-knot Nematodes in Wild Peach, Prunus kansuensis

Abstract

<jats:p>The root-knot nematode (RKN) <jats:italic>Meloidogyne incognita</jats:italic> can cause severe crop loss in economically important <jats:italic>Prunus</jats:italic> species like peach (<jats:italic>P. persica</jats:italic>), almond (<jats:italic>P. communis</jats:italic>), plum (<jats:italic>P. salicina</jats:italic>), and apricot (<jats:italic>P. armeniaca</jats:italic>). Some peach rootstock, including Nemaguard (<jats:italic>P. persica</jats:italic>), Nemared (<jats:italic>P. persica</jats:italic>), and Myrobalan plum (<jats:italic>P. cerasifera</jats:italic>), display significant resistance to RKN. We present a genetic linkage map constructed by using simple sequence repeat (SSR) and sequence-related amplified polymorphism (SRAP) for a peach backcross population (190 individuals) of RKN-resistant ‘Honggengansutao’ (<jats:italic>P. kansuensis</jats:italic>) and susceptible ‘Bailey’ (<jats:italic>P. persica</jats:italic>). Degenerate primers designed from conserved motifs of known plant resistance gene (<jats:italic>R</jats:italic>) products were used to amplify genomic DNA sequences. Twenty-two resistance gene analog (RGA) sequences were selected from 48 RGAs with open-reading frames to design sequence-tagged site markers. The linkage map of ‘Honggengansutao’ is composed of 138 loci (30 SSRs, 102 SRAPs, five RGAs, and one morphological marker for RKN resistance) assigned to eight linkage groups. The map covers 616 cM of the peach genome with an average marker spacing of 4.9 cM. The five RGAs were mapped to Groups 2, 7, and 8. One gene (designated <jats:italic>PkMi</jats:italic>) involved in resistance to RKN was mapped to Group 2 (which also includes the known RKN-resistance <jats:italic>RMia</jats:italic> gene). BLASTN analysis mapped all RGAs to the peach genome sequence. The map constructed in the study will aid future rootstock breeding with marker-assisted selection to identify additional candidate RGA sequences.</jats:p>

Inheritance of resistance to the peach root‐knot nematode (Meloidogyne floridensis) in interspecific crosses between peach (Prunus persica) and its wild relative (Prunus kansuensis)

“…An accession of P. kansuensis in China was reported to also contain a R gene ( PkMi ) conferring “immunity” to MI. The PkMi gene was hypothesized to be an allele of RMia which controls resistance to MI and MA in peach sources (Cao et al., ), raising the possibility for broad‐spectrum resistance in P. kansuensis similar to the Ma gene in P. cerasifera . Further investigation on the resistance spectrum of P. kansuensis is warranted considering the observed infestation of other RKN species in some commercial peach orchards in Florida.…”

“…The parental genotypes P. kansuensis and P. persica cultivars (‘Okinawa,’ ‘Flordaguard’ and ‘UFSharp’) represent different levels of nematode resistance and were crossed to generate segregating populations. All the hybrids originated from a single P. kansuensis genotype labelled Prunus kansuensis “A.” The host status of P. kansuensis to MF is not previously known, although it has been found to be highly resistant (gall index = 0) to MI (Cao et al., ). ‘Okinawa’ peach is resistant to MI and MJ but susceptible to MF (Sharpe, Hesse, Lownsbery, & Hansen, ; Sherman & Lyrene, ); artificial inoculation in the greenhouse revealed its susceptibility also to the “MFGnv14” isolate (D. Dickson, pers.…”

“…Thirteen F 2 and BC 1 F 1 populations tested in this study originated from P. kansuensis to MF is not previously known, although it has been found to be highly resistant (gall index = 0) to MI (Cao et al, 2011).…”

“…An accession of P. kansuensis in China was reported to also contain a R gene (PkMi) conferring "immunity" to MI. The PkMi gene was hypothesized to be an allele of RMia which controls resistance to MI and MA in peach sources (Cao et al, 2011), raising the possibility for broad-spectrum resistance in P. kansuensis similar to the Ma gene in P.…”

“…In the genus Prunus , major RKN R genes have been identified in: Myrobalan plum ( Ma ) and Japanese plum ( Rjap ) (Claverie et al., ); peach cultivars ‘Nemared,’ ‘Nemaguard,’ ‘Shalil’ and ‘Juseitou’ ( RMia ) (Claverie et al., ; Duval et al., ; Esmenjaud et al., ; Yamamoto & Hayashi, ); almond ‘Alnem’ ( RMja ) (Van Ghelder et al., ); and, more recently, wild peach P. kansuensis ( PkMi ) (Cao et al., ). Resistance found in the subgenus Amygdalus (peach and almond) is limited in spectrum, and none of the domesticated sources are resistant against MF (Handoo et al., ), whereas in the subgenus Prunophora , accessions of Japanese plum and Myrobalan plum have shown broad and high level of resistance to RKN including MF (Esmenjaud et al., ; Lecouls et al., ; Rubio‐Cabetas et al., ).…”