Proceedings of the XLVI Italian Society of Agricultural Genetics - SIGA Annual Congress

Giardini Naxos, Italy - 18/21 September, 2002

ISBN 88-900622-3-1

Poster Abstract - 1.36

MAPPING OF SSR, AFLP AND RGA MARKERS TO IDENTIFY FIRE BLIGHT RESISTANCE QTLs IN PEAR

CHIODINI R.*, PIERANTONI L.*, DONDINI L.*, TARTARINI S.*, BAZZI C.**

*) Dipartimento di Colture Arboree, Università di Bologna

**) Dipartimento di Scienze e Tecnologie Agroambientali, Università di Bologna

fireblight, pear, SSR, AFLP, RGA

Since several years, the pear production in Emilia Romagna has been strongly affected by fire blight. The lack of known monogenic resistance, together with the poor fruit quality of the resistant genotypes represent the main limiting factors in pear breeding programs. Moreover the pear genoma is not enough characterised yet, especially for resistance genes.

This work is the beginning of a phenotypic and molecular study on fire blight resistance. A population derived from the Passa Crassana x Harrow Sweet cross, respectively susceptible and resistant cultivars, has been analysed with resistance assays and molecular markers. The inoculations for the susceptibility evaluation have been conducted on the population during springtime for three years. The data show a continuous distribution of the symptom classes, thus confirming the poligenic nature of the trait.

A preliminary genetic map has been constructed using SSR, RGA and AFLP markers.

Some SSR markers, previously isolated and mapped in apple, have been transferred successfully in pear allowing thus to obtain markers well spread in the genome and to verify a certain degree of syntheny between the two species.

RGA sequences have been cloned from resistant cultivars (Old Home, Harrow, Sweet, US 309) to map markers potentially linked to the resistance genes.

The genetic map is being saturated by AFLP markers. A modified AFLP technique, where one of the two primers is substituted by a primer designed on highly conserved resistance sequences, has been used in order to amplify and map sequences theoretically close to resistance genes.

A QTL analysis with the Kruskal-Wallis single locus on all the data collected so has found out a relationship between some molecular markers and a certain degree of fire blight resistance. The possible QTLs yet identified have to be confirmed with further work.