Variability within Accochyta fabae Populations in Syria and Identification of Sources of Resistance within Syrian faba bean landraces

Ali Subeh
General Commission for Scientific Agricultural Research-
Lattakia Research Center
Tishreen University, Faculty of Agriculture
 2008

Abstract

Faba bean samples infected with Ascochyta fabae were collected from different plant parts (leaves, stems, pods) from many Syrian provinces (Lattakia, Tartous, Idleb, Hama, Aleppo, Daraa). After isolation, purification was done by hyphal tips and single spore methods. 264 isolates of Ascochyta fabae were obtained. Morphological characterization was performed on the isolates and included: colony color, mycelium texture, growth rate and sporulation. Huge differences between isolates were recorded. 38% of the isolates had differences between replicates of the same isolate. There was no correlation between morphological parameters, so it was not possible to group the isolates according to their morphology.
The pathogenicity of 40 Ascochyta fabae isolates originated from different Syrian provinces was studied using 7 differentials. There were no correlation between morphological characteristics and the pathogenicity of the isolates, and there was no correlation between geographical origin of the isolates and the plant parts from where the fungus was isolated with morphological characteristics and pathogenicity.
Genetic Disimilarity was evaluated using two techniques AFLP, MP_PCR, and large genetic variability between isolates were recorded (GD=0.89-0.99); most of genetic variability were within the populations of Ascochyta fabae, whereas genetic similarity was medium among populations (‰0.31). Two mating types (MAT1-1, MAT1-2) were detected in fungal samples collected from  Syrian provinces and one highly infected single leaf, implying the possibility of forming sexual stage of the fungus (Didymella fabae).
Fifty Syrian accessions of faba bean from ICARDA gene bank were screened for Ascochyta blight in two years (2006-2007).
One accession (BPL2761) was moderately resistant in the first year, whereas, in the second year, all accessions were susceptible when more aggressive isolates were used in the inoculation.