Genetic mapping of the pear scab resistance gene Vnk of Japanese pear cultivar Kinchaku

Abstract

Pear scab (caused by Venturia nashicola) is one of the most harmful diseases of pears, especially Japanese and Chinese pear species. The molecular identification and early selection of resistant plants could greatly improve pear breeding. We have identified the position of the scab resistance gene, designated Vnk in an indigenous Japanese pear cultivar Kinchaku, within the pear genome by using simple sequence repeat (SSR) markers derived from pear and apple. The position of Vnk was identified in the central region of linkage group 1 of Kinchaku. Several amplified fragment length polymorphism (AFLP) markers linked to Vnk were obtained by bulked segregant analysis. Among them, the AFLP marker closest to Vnk was converted into a sequence tagged site (STS) marker. Four random amplified polymorphic DNA (RAPD) markers previously found to be loosely associated with Vnk (Iketani et al. 2001) were successfully converted into STS markers. Six markers (one SSR Hi02c07 and five STSs converted from AFLP and RAPD) showed tight linkages to Vnk, being mapped with distances ranging from 2.4 to 12.4 cM. The SSR CH-Vf2, which was isolated from a BAC clone of the contig containing the apple scab gene Vf, was mapped at the bottom of linkage group 1 in Kinchaku, suggesting that the Vnk and Vf loci are located in different genomic regions of the same homologous linkage group.

The Validity of Marker-assisted Selection Using DNA Markers Linked to a Pear Scab Resistance Gene (Vnk) in Two Populations

“…In this study, we analyzed 5 DNA markers linked to the 'Kinchaku' Vnk scab resistance reported in Terakami et al (2006) to two populations of the progenies, and confirmed the results with a standard V. nashicola inoculation test.…”

“…A RAPD marker linked to a gene for susceptibility to pear black spot disease was reported (Banno et al, 1999;Iketani et al, 2001) and the gene was mapped on linkage group (LG) 11 50 (Terakami et al, 2007). The scab resistance gene (Vnk) from 'Kinchaku' was mapped in the central region of LG1 (Terakami et al, 2006;Yamamoto et al, 2004). Terakami et al (2006) reported one SSR and 5 STS markers closely linked to Vnk.…”

“…The scab resistance gene (Vnk) from 'Kinchaku' was mapped in the central region of LG1 (Terakami et al, 2006;Yamamoto et al, 2004). Terakami et al (2006) reported one SSR and 5 STS markers closely linked to Vnk. These DNA markers could improve selection efficiency in Japanese pear breeding programs.…”

Fluorescent Staining and Fluorescence in situ Hybridization of rDNA of Chromosomes in Pear (Pyrus spp.)

“…In addition, detection of the physical locations of useful gene loci has progressed in important crops and vegetables (Iwano et al, 1998;Ohmido et al, 1998). Therefore, physical mapping of useful genes, such as for scab resistance and black spot disease susceptibility (Terakami et al, 2006, should be conducted in pears. …”

Recent Progress on Studies of Chromosome Observation in Deciduous Fruit Trees

“…Therefore, physical mapping of useful genes, for instance, scab resistance and black spot disease susceptibility in pear (Terakami et al, 2006, should be conducted.…”