PCR ANALYSIS OF THE VIRAL COMPLEX-ASSOCIATED WITH LA FRANCE DISEASE OF AGARICUS-BISPORUS

Reverse transcription PCR analysis was used to investigate the involve ment of two RNA-genome viruses, La France isometric virus (LIV) and mu shroom bacilliform virus (MBV), in the etiology of La France disease o f the cultivated mushroom Agaricus bisporus, Reverse transcription PCR amplification of sequences targeted to the genomes of LIV and MBV, wi th a sensitivity of detection of <10 fg of viral RNA, showed diseased mushrooms to be either singly infected by LIV or doubly infected by LI V and MBV. Of 70 geographically diverse diseased mushroom isolates, 10 0% were infected by LIV, whereas almost 60% of these isolates were coi nfected by MBV. Of 58 mushroom isolates determined to be free of infec tion by LIV, 3 were found to be infected by MBV. This represents the f irst documented report of the independent replication of these two vir uses. Our data support the hypothesis that La France disease is associ ated with infection by two autonomously replicating viruses in which L IV is the primary causal agent and MBV, although possibly pathogenic a nd capable of modulating symptoms, is not required for pathogenesis.