The Effect of Paclobutrazol, Growth Retardant, on Cotton Growth and Verticillium Wilt (Verticillium dahliae Kleb.)

Abstract

The user has requested enhancement of the downloaded file. Materials and Methods Fifteen PBZ concentrations were tested in vitro for their effects on O. novo-ulmi daily growth rates. Concentrations (ppm) used were 0, 0.5, 1, 1.5, 2, 4, 6, 8, 10, 12, 20, 40, 50, 100, 400. Cultures were grown at 25°C in the dark. Isolates were measured every 23-25 hours for 10 days. Plates were marked so that isolates were measured along the same two perpendicular planes each time (images 1 & 2). Daily growth rates were calculated as the difference in average diameter between each day. Due to the sample size and daily growth rates of approximately 1 mm unit of resolution of the diameter measurements, the data did not reliably meet the assumptions of normality and homogeneity of variance required for a standard ANOVA. Data was evaluated in R utilizing the ANOVA permutation test aovp of the lmperm library. Tukey's HSD test was applied to the resulting data to determine the concentrations which were statistically significant at the p=0.05 from the control. Results • Colonies did not grow on PDA media with 20 ppm or higher concentrations (data not shown) • Growth rates were statistical different for 0.5, 1, 1.5, 2, 4, 6, 8, 10, 12 ppm for the first seven days compared to the growth rate of the negative control (figure 1) • Colonies growing on paclobutrazol-amended media appeared to have more dense and less fibrous hyphal (image 4) growth than colonies grown on unamended PDA (image 3) 1. Shaul, O., Elad, Y. & Zieslin, N. 1996. Suppression of Botrytis blight in cut rose flowers with gibberellic acid. Effects of exogenous application of abscisic acid and paclobutrazol.