The article about pencycuron (part 7)

The minimum inhibitory concn of the fungicides flutolanil, pencycuron, validamycin and mepronil against the fungus was >400 ppm, while that of benomyl and triflumizole was 12.5 ppm Mycelial growth and conidia formation were greatest at 30 and 27.5 degrees C, resp. Both beta -tubulin genes of R-C and Rh-131 had 1582 nucleotides encoding a protein of 445 amino acids, showing 98% homology in amino acid sequences between them. It was found that codons at 103, 236 and 267 for lysine, valine and isoleucine in R-C were replaced by codons for methionine, isoleucine and methionine in Rh-131, respectively. No inhibitory effect of pencycuron on the tubulin assembly was observed. A dilute solution of azoxystrobin applied to seedlings controlled damping-off more effectively than hymexazol. The incidence of root rot of sugarbeet inoculated with Rhizoctonia solani was decreased by applications of 268 or 536 g a.i./ha azoxystrobin. The application of a dilute solution of azoxystrobin to seedlings just before transplanting or to the roots before inoculation was as effective as treatment with pencycuron 50% wettable powder. With the exception of ECOFIT, that was applied as a soil drench directly after planting, the products were mixed together with the pathogens into the potting substrate immediately before planting. Under these conditions, considerable variation in efficacy was observed between the products. Against R solani, SOILGARD was as efficacious as the chemical standard pencycuron. Also, SOILGARD was the only biocontrol product that gave significant control of P ultimum. The other biocontrol products showed some efficacy against the two pathogens, but in most cases the level of disease control was not statistically significant, A comparison of performance in heat-treated and nontreated potting substrate indicated that, in the case of R solani, activity of all biocontrol products was enhanced by heat-treatment. On the contrary, control of P ultimum tended to be weaker in heat-treated than in nontreated potting medium. When laboratory preparations based on the active microbial ingredients from SUPRESIVIT and SOILGARD were applied at equal rates, control of R solani by the SOILGARD-preparation was superior to that by the SUPRESIVIT-preparation, despite a higher number of propagules in applied amounts of the latter. The results were corroborated by in vitro experiments in which the extract prepared from rice plants harvested 10 days after soil-drenching treatment showed an inhibitory effect to the mycelial growth of R solani on water agar. Seed treatment with pencycuron was not effective in controlling sheath blight infection. However, the metabolic intermediates of pencycuron, cyclopentyl-3-phenylurea and phenylurea, were not effective. Following HPLC analysis, 78.0 ppm/g FW pencycuron was detected from rice plants harvested 10 days after soil-drenching. In the greenhouse, pencycuron inhibited binucleate Rhizoctonia, R oryzae, or R solaniin vitro and reduced Rhizoctonia root rot. Pencycuron also inhibited G graminis var tritici strains in vitro and slightly reduced take-all disease in the greenhouse. Moreover, pencycuron seed treatment protected plants against a disease mixture of Rhizoctonia root rot and take-all. Pythium spp were not inhibited by pencycuron in vitro. Pencycuron did not adversely affect seedling emergence, nor did it inhibit rhizosphere colonisation by Pseudomonas fluorescens biocontrol strain 2-79.

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