OLIGONUCLEOTIDE FINGERPRINTING DETECTS GENETIC DIVERSITY AMONG ASCOCHYTA-RABIEI ISOLATES FROM A SINGLE CHICKPEA FIELD IN TUNISIA

Fifty isolates of Ascochyta rabiei (Pass.) Labr. were hierarchically s ampled from four well-separated lo cations of a single chickpea field in Beja (Tunisia), and single-spored. DNA was isolated from in-vitro-g rown mycelia, digested with HinfI or RsaI, and hybridized to a set of synthetic oligonucleotides complementary to simple repetitive sequence s. According to the fingerprint patterns derived from the probes (CA)( 8), (CAA)(5), (CAT)(5) and (GATA)(4), 12 different fungal haplotypes w ere found at various frequencies within the investigated field. Seven haplotypes were confined to one location only, four occurred at two, o ne at three, and none at all four locations. Most of the genetic varia bility originated from diversity within, rather than between, location s. In some cases, more than one haplotype was isolated from the same l esion of a single host plant. Genetic distances between isolates, as c alculated from band-sharing data, varied between 0.05 and 0.22. Relate dness between the different haplotypes was evaluated by cluster analys is using UPGMA.