Identification and mapping of a locus conferring plum pox virus resistance in two apricot-improved linkage maps

Abstract

Sharka disease, caused by the plum pox virus (PPV), is one of the major limiting factors for stone fruit crops in Europe and America. In particular, apricot is severely affected suffering significant fruit losses. Thus, PPV resistance is a trait of great interest for the apricot breeding programs currently in progress. In this work, two apricot maps, earlier constructed with the F 1 'Goldrich × Currot' (G×C) and the F 2 'Lito × Lito'-98 (L×L-98) populations, have been improved including 43 and 37 new simple sequence repeat (SSR) loci, respectively, to facilitate PPV resistance trait mapping. Screening of PPV resistance on the segregating populations classified seedling phenotypes into resistant or susceptible. A non-parametric mapping method, based on the Kruskal-Wallis (KW) rank sum test, was initially used to score marker-trait association, and results were confirmed by interval mapping. Contrary to the putative digenic model inferred from the phenotypic segregations, all significant markers for the KW statistic (P<0.005) mapped in a unique region of~21.0 and 20.3 cM located on the upper part of the G1 linkage group in 'G×C' and 'L×L-98' maps, respectively. According to the data, PPV resistance is suggested to be controlled by at least one major dominant locus. The association between three SSRs distributed within this region and the PPV resistance was tested in two additional populations ('Goldrich × Canino' and 'Lito × Lito'-00) and breeding program parents. The marker ssrPaCITA5 showed the highest KW value (P<0.005) in all cases, pointing out its usefulness in marker-assisted selection.

Genetic Apricot Resources and their Utilisation in Breeding

“…Minor QTL were discovered in the Polonais 9 SEO progeny in LG3 and LG5 of both SEO and Polonais [50]. The main QTL on LG1 was upheld by Sicard et al [51] establishing new microsatellite (SSR) markers flanking the QTL and by Lalli et al [52] in a backcross population of SEO 9 Vestar and was again confirmed by Soriano et al [46] in the extended F2 Lito selfed progeny. Most of the resistance determinants shown above were characterized using the PPV-D strain as a source of inoculum and, at present, the only resistances specific to the PPV-M strain are those endorsed in the BC1 SEO xVestar [52] and in P. davidiana [44].…”

“…A first determinant was mapped on linkage group 1 (LG1) by using an F1 progeny of Goldrich 9 Valenciano [46]. These studies were also verified by a quantitative trait locus (QTL).…”

“…LG1 by the analysis of F1 and F2 progenies of Stark Early Orange (SEO) [48] and its progeny Lito [46,49]. Minor QTL were discovered in the Polonais 9 SEO progeny in LG3 and LG5 of both SEO and Polonais [50].…”

Allelic variation of simple sequence repeats markers linked to PPV resistance in Chinese apricot

“…The disease spread from its origin in the Balkan countries to most of the European subcontinent and the areas around the Mediterranean basin. It is one of the most limiting factors in apricot production and results in deformed, unripen and unmarketable fruits (Sicard et al 2008;Soriano et al 2008). The PPV epidemic also appears in Russia, India, Kazakhstan and Pakistan (EPPO Bulletin 2006), its first occurrence in Japanese apricot (P. mume Sieb.…”

“…'SEO' is the resistant resource (Karayiannis et al 2008), but 'Goldrich' and 'Harcot' are tolerant resources to PPV (Stylianidis et al 2005). These cultivars are used as donors for resistance in conventional breeding based on the crosses between the PPV-resistant and the local cultivars susceptible to PPV virus throughout Europe (Hurtado et al 2002;Soriano et al 2008). Previous study indicates that this PPV resistance mechanism might have been directly or indirectly introduced from non-domesticated species found in China, for example P. sibirica, P. mandshurica, P. mume, P. sibirica var.…”