Genetic diversity in Monilinia laxa populations in stone fruit species in Hungary.

The objectives of this study were firstly, to determine the genetic diversity of Monilinia laxa isolates from Hungary, using the PCR-based inter-simple sequence repeat (ISSR) and randomly amplified polymorphic DNA (RAPD) technique; secondly, to prepare genetic diversity groups based on the dendrograms; and finally, to select some relevant isolates to study their fungicide sensitivity. 55 and 77 random amplified polymorphic ISSR and RAPD markers, of which 23 and 18 were polymorphic and 32 and 59 monomorphic, respectively, were used to assess the genetic diversity and to study the structure of M. laxa populations in Hungary. 27 isolates out of 57 ones were confirmed as M. laxa from several orchards (subpopulations) in three geographical regions, in various inoculum sources and in various hosts, were used. 10 fungicides and 12 isolates selected from genetic diversity groups based on the ISSR dendrograms were used to determine the fungicide sensitivity of the selected isolates. The analysis of population structure revealed that genetic diversity within locations, inoculum sources and host (H(S)) accounted for 99 % of the total genetic diversity (H(T)), while genetic diversity among locations, inoculum sources and host represented only 1 %. The relative magnitude of gene differentiation between subpopulations (G(ST)) and the estimate of the number of migrants per generation (Nm) averaged 0.005-0.009 and 53.9-99.2, respectively, for both ISSR and RAPD data set. The results obtained in dendrograms were in accordance with the gene diversity analysis. Grouping of isolates in the dendrograms was irrespective of whether they came from the same or different geographical locations. There was no relationship between clustering among isolates from inoculum sources and hosts. In the fungicide sensitivity tests, five isolates out of 12 were partly insensitive to boscalid+piraclostrobin, cyprodinil, fenhexamid or prochloraz. Obtained results in genetic diversity of M. laxa populations are discussed together with implications for the management of brown rot.