Characterization and protein fingerprinting of Botrytis cinerea isolates /

Botrytis cinerea isolates collected from Niagara region were treated with different concentrations of the fiingicide, iprodione to test their sensitivity to this fungicide. These Botrytis cinerea isolates were divided into two groups according to their sensitivity to iprodione. Those isolates whose growth was inhibited by iprodione at concentrations < 2|i,g/nil were classified as sensitive isolates. Isolates that were able to show considerable growth at 2|j,g/ml iprodione were classified as resistant isolates. Resistant and sensitive isolates were compared for their morphological and growth characteristics, conidial germination, virulence on grape berries and protein banding profiles. The fungicide iprodione at a concentration of 2|xg/nil inhibited mycelial growth, sporulation and conidial germination of sensitive isolates but not those of resistant isolates. The inhibitory effect of the fungicide was greater on mycelial growth than on conidia germination of the sensitive isolates. Sensitive isolates produced no sclerotia whereas resistant isolates produced large number of sclerotia. The fungicide iprodione affected sclerotial production in the resistant isolates. The number of sclerotia was decreased by the increase of iprodione in the medium. Sporulation of resistant isolates was improved significantly in the presence of iprodione. The resistant isolates were as virulent as the sensitive isolates on grape berries. The sensitive and resistant isolates showed similar protein banding profiles in the absence of iprodione in polyacrylamide gel electrophoresis studies. Similar protein profiles were also observed when these isolates were grown in the presence of low iprodione concentration (0.5|ig/nil). However, in the presence of concentration (0.5|ig/nil). However, in the presence of iprodione at concentration of 5|Xg/nil, one protein band with approximate molecular weight of 83 KDa was present in the growing resistant isolates (and the controls) but was missing in the inhibited sensitive isolates.

Sensitivities of Ontario isolates of Venturia inaequalis to metiram /

The effects of metiram (Polyram 80 DF) on the growth of Venturia inaequalis, cause of apple scab, and the degradation of metiram were examined in culture media. Samples of V. inaequalis conidia were collected from nine orchards in 1998 and six orchards in 1999 and tested for sensitivity. Samples were plated on water agar amended with metiram or mancozeb. Mean EC50 values (effective concentration of fungicide required to inhibit germination of half the conidia) for each population were calculated. The mean EC50 values for metiram ranged from 0.26 - 1.20 ^ig metiram a.i./ml, with differences (Student Newman Keul's Test (SNK), a=0.05) between populations. EC50 values for mancozeb ranged from 0.06 - 0.58 which were also different (SNK, a=0.05). Five of these populations were examined for mycelial growth sensitivity to metiram by testing 30 monoconidial isolates from each population on metiram amended potato dextrose agar. Mean EC50 values for populations were calculated and ranged from 3.44-5.94 |ig metiram/ml, and showed differences (Friedman Test, a=0.05). As the EC50 values obtained are far less than the concentrations applied in the field, results indicate that Ontario populations of V. inaequalis are still sensitive to metiram and mancozeb. The stability of metiram in PDA at 22°C was studied over a 10-day period. The initial concentration of metiram decreased by approximately 50% within the first day, and continued to decline slowly, to approximately 20% of the initial concentration. The factors possibly affecting initial metiram degradation, including agar, heat, and the use of glass or polystyrene Petri dish composition were examined. The effects from the polystyrene in the Petri dish composition were negligible, however more studies must be done to examine metiram degradation during the first 24 hours of preparation.