Molecular typing of red and green phenotypes of 'Bon rouge' pear trees, with the use of microsatellites

'Bon Rouge' is a red pear cultivar derived from a rare, spontaneous bud mutation of the green pear cultivar William's Bon Chretien (Bartlett). We have observed that the Bon Rouge trees generate revertants at a high frequency to produce green tissues in clonal stripes on stems and fruit. We aim to establish whether this instability is the result of chimerism or genetic instability, and to examine the molecular mechanism of this trait. A closed cross between 'Bon Rouge' and 'Packham's Triumph' pears generated an F, population with a 1:1 segregation of the red:green phenotype, indicating a simple Mendelian inheritance of this trait. However, this does not address the mechanism of the reversion. We are currently mapping apple and pear simple sequence repeats (SSRs/Microsatellites) on the F, progeny. Both apple and pear microsatellites were used in this study because of the high level of cross-species cross-reaction. Microsatellites that show a high level of polymorphism are being used to construct a linkage map with the aim of identifying those markers that are tightly linked to the gene controlling the red/green trait.