Characterization of Verticillium albo-atrum Field Isolates Using Pathogenicity Data and AFLP Analysis

Area of Science:

• Plant Pathology
• Mycology
• Molecular Biology

Background:

• Hop wilt, caused by Verticillium albo-atrum, has led to significant economic losses in Slovenia since 1997.
• Distinct pathotypes, PG1 (mild) and PG2 (lethal), cause varying disease severity in hops.

Purpose of the Study:

• To genetically differentiate isolates of Verticillium albo-atrum from hop plants with different wilt severities.
• To confirm the genetic distinctness between V. albo-atrum and V. dahliae.
• To investigate the genetic basis of virulence in hop wilt pathogens.

Main Methods:

• Amplified Fragment Length Polymorphism (AFLP) was employed to analyze genetic polymorphism among 20 V. albo-atrum isolates and 2 V. dahliae isolates.
• Pathogenicity tests were conducted on hop cultivars to confirm virulence differences.
• Cluster analysis was used to group isolates based on AFLP data.

Main Results:

• AFLP analysis successfully separated V. albo-atrum and V. dahliae into distinct clusters.
• V. albo-atrum isolates were further divided into two groups: A1 (PG1 pathotype, cucumber, petunia) and A2 (PG2 pathotype).
• Genetic differentiation correlated with virulence levels, indicating distinct hop V. albo-atrum pathotypes.

Conclusions:

• The study confirms the genetic distinctness of V. albo-atrum and V. dahliae species.
• Amplified Fragment Length Polymorphism (AFLP) is effective in differentiating hop Verticillium albo-atrum pathotypes based on virulence.
• Genetic variation within pathotypes is minor, but clear separation exists between virulent and less virulent hop isolates.