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

Verona, Italy - 24/27 September, 2003

ISBN 88-900622-4-X

Poster Abstract - 5.12

INDIVIDUATION OF cDNA-AFLP MARKERS IN APPLE PROLIFERATION PHYTOPLASMA RESISTANT APPLE ROOTSTOCKS

M. MOSER*, W. JARAUSCH**, M. KOMJANC*, E. VINDIMIAN*, E. SEEMUELLER***, R. VELASCO*

*) Istituto Agrario S.Michele a/A Via E.Mach, 1 38010 S.Michele a/A

**) Centrum Grüne Gentechnik (CGG) Neustadt an der Weinstrasse, Germany

***) Biologische Bundesanstalt für Land- und Forstwirtschaft (BBA) Dossenheim, Germany

apple proliferation, cDNA-AFLP, differential screening

Apple proliferation (AP) disease is associated with phytoplasmas, phloem – restricted bacteria of the class Mollicutes, which are naturally transmitted by leafhopper or psyllid vectors but which can also be spread by man through grafting or vegetatively propagated AP-infected material.

Witches brooms, enlarged stipules and small sized fruits with incomplete coloration are the most typical symptoms of AP. Their gravity depends on the infected varieties.

Unfortunately, phytoplasmas cannot be cultured on artificial medium and can only be maintained in the infected plant. The introduction of methods based on DNA research could greatly improve the studies on phytoplasma-plant interaction.

In the past 15 years resistant genotypes of apple rootstocks were selected and re-crossed with commercial genotypes in Germany. These rootstock selections were demonstrated to be field resistant to AP disease and experimentally inoculated plants showed a high rate of recovery. They are to vigourous to be of commercial interest but they are a possible starting material for new analyses to understand the mechanism of the disease and for the marker assisted selection of new AP phytoplasma resistant rootstocks.

The following genotypes have been used in order to characterize the resistance phenomenon:

M9: Malus domestica rootstock, susceptible genotype

4551(M. domestica cv. Laxton Superb x M. sieboldii): field resistant rootstock selection, the resistance phenotype is inherited by M. sieboldii

H0909 (4551 x M9): backcross of 4551 with susceptible M. domestica genotype, still field resistant.

The objectives of this work are:

• Selection of cDNA-AFLP markers suitable for a marker assisted selection in the crossing of resistant rootstocks and commercial non-vigourous rootstocks
• Investigation of the differential expression of the plant genes during the infection by the AP phytoplasma
• Identification of possible mechanisms involved in the resistance or tolerance to AP phytoplasma.

The two techniques used are cDNA-AFLP and Differential Screening.

Several bands have been isolated by cDNA-AFLP which are present in both the resistant genotypes but not in the susceptible genotype (M9). Our intention is further to identify a pool of resistance related genes by differential screening using the following subtractive cDNA libraries H0909-D4551; D4551-M9; H0909-M9.

Results obtained from differential screening and cDNA-AFLP will be discussed.