DNA MARKERS IDENTIFY VARIATION IN AUSTRALIAN POPULATIONS OF UNCINULA NECATOR

Restriction fragment length polymorphisms (RFLPs) were identified amon g total DNA hom clonal lines of Uncinula necator when cloned sequences of total U. necator DNA were used as probes. Four probes, pUnP14, pUn P27, pUnE21 and pUnE4, hybridized to multiple-copy sequences and, with the exception of pUnE4, detected genetic variation among clonal lines of U. necator. Clones pUnP14, pUnP27 and pUnE4 produced banding patte rns that were stable for DNA extracted from different asexual generati ons of U. necator clonal lines over at least 15 months. In addition, c rones were evaluated for species specificity. Clones pUnP27 and pUnE4 detected only U. necator sequences in total DNA from infected grapevin e leaves. Clones pUnP14 and pUnE4 did not hybridize to total DNA from a range of fungi. Genetic diversity in a sample of the Australian U. n ecator population was investigated; 15 genotypes were identified among 29 U. necator clonal lines examined. Genetic variation was detected i n samples collected within micro-geographical areas, for example, diff erent genotypes representing both mating types of U. necator were dete cted on a single plant of Vitis amurensis. RFLP analysis of the bandin g patterns produced using pUnP14, pUnP27 and pUnE21, identified two br oad genetic groups, designated A and B. Analysis of DNA fragment patte rns obtained using the polymerase chain reaction (PCR) and the plant i ntron splice junction (ISJ) primer RI also supported the allocation of U. necator clonal lines into groups A and B.