Sensitivity to triadimefon, a triazole demethylation inhibitor (DMI), of Erysiphe graminis f. sp, tritici populations collected in 1992 from fields of the wheat cultivar Absolvent in the Annapolis Valley and Colchester County of Nova Scotia, Canada, was studied in vitro. E. g. f. sp. tritici isolates were collected before, as well as at two and six weeks after triadimefon application. Exposing powdery mildew fungal populations from the Annapolis Valley to the selection pressure of triadimefon resulted in an increase in the log(10) transformed mean value of EC(50) from 0.30 mu g/mL for population of isolates collected before triadimefon application, to 0.85 mu g/mL for population of isolates collected six weeks after triadimefon application. In the case of Colchester County, the log,, transformed mean value of EC(50) increased from 0.34 mu g/mL to 1.04 mu g/mL for isolates collected before, and six weeks after triadimefon application, respectively. The frequency distribution of EC(50) values within each population of fungal isolates collected at each sampling time was lognormal. The findings suggest that isolates of E. g. f. sp. tritici with reduced sensitivity to triadimefon had existed in winter wheat fields before the fungicide was applied. After exposing fungal populations to triadimefon more isolates with reduced sensitivity were built-up, and by the end of the season they dominated the populations.

This study was initiated to quantify the baseline sensitivity of wheat powdery mildew [Erysiphe graminis f. sp. tritici] populations to triadimefon, a sterol demethylation inhibitor (DMI). In 1991, sensitivities (EC(50) values) of 240 single pustule-derived isolates of E. graminis f. sp, tritici were studied in vitro. Isolates were collected from triadimefon-treated and nontreated winter wheat (cvs. Absolvent and Borden) fields in the Annapolis Valley and Colchester County of Nova Scotia, Canada. The log(10) transformed values of EC(50) for the eight fields ranged from -1.00 to 2.43 mu g mL(-1). Means of the log(10) transformed values of EC(50) Of the eight field populations ranged from 0.29 to 1.12 mu g mL(-1) with a combined mean of 0.76 mu g mL(-1). The variance of sensitivities determined for the eight populations was homogenous, and all EC(50) values could be combined in one distribution. A sample size of 30 was sufficient to detect differences of 1.32 or more times and higher the difference between mean log(10)(EC(50)) values of any two populations.

The competitive abilities of randomly selected triadimefon-sensitive (S) and triadimefon-resistant (R) single-pustule derived isolates of Erysiphe graminis f. sp. tritici obtained from triadimefon-treated and -untreated fields of the Annapolis Valley (AV), Nova Scotia, were tested. In 1991, mixed inoculations of S/R isolates in 75:25, 50:50, and 25:75 ratios were studied in vitro in the absence of triadimefon on wheat cultivar Absolvent. in 1992, a 50:50 (S/R) inoculation ratio was used to study the competition between R and S isolates collected from triadimefon-treated fields in the AV. Results indicated that in the absence of triadimefon the mean ECS, values of mixtures of various S/R ratios tested in 1991 and of the 50:50 ratio tested in 1992 decreased significantly (P < 0.05) after five generation cycles. Resistant isolates were less fit (less competitive) than sensitive ones in the absence of triadimefon.

Measurements were made on electron micrographs of six human anterior pituitary glands of the maximal diameters of secretory granules in 130 cells, average 91 granules per cell. This was done in an attempt to classify the various hormone types solely by differences in the mean diameters of the secretory granules. The range of diameters in nanometers could be segregated into six subgroups of the following suggested functions: 135.5 +/- 13.6 TSH, 181.6 +/- 9.3 LH, 226.0 +/- 19.4 FSH, 356.8 +/- 30.5 ACTH/MSH, 452.9 +/- 23.8 GH, 559.9 +/- 38.0 prolactin.

Diameters of secretory granules in thyrotrophs in gonadotrophs were measured in electron micrographs of operation specimens of 4 pituitary glands and of the secretory granules in operation specimens of 10 clinically non-functioning chromophobe adenomas. The mean diameter of the thyrotroph granules was 137 plus or minus 26 nm, of the gonadotrophs 204 plus or minus 38 nm, of 9 of the adenomas 141 plus or minus 20 nm and of the remaining adenoma 248 plus or minus 67 nm. The significance of the close correlation in granule size in most of the adenomas with that of thyrotrophin granules is discussed briefly.