Temperature, Moisture, and Seed Treatment Effects on Rhizoctonia solani Root Rot of Soybean

Abstract

The effects of temperature and soil moisture on infection and disease development by Rhizoctonia solani on soybean were studied individually. In addition, the anastomosis group of R. solani isolates recovered from soybean from 35 fields in 15 counties was determined. All of the 44 isolates recovered in this study were AG-2-2 IIIB. Five isolates of R. solani were able to infect and colonize soybean roots and hypocotyls at 20, 24, 28, and 32°C in growth chamber studies. The temperatures evaluated in this study were not limiting to the isolates tested. In greenhouse studies, nine R. solani isolates and a noninoculated control were evaluated at 25, 50, 75, and 100% soil moisture holding capacity (MHC). Root weights were greater and percent stand averages higher at 50 and 75% than at 25 or 100% MHC; however, as percentage of control, the main effect on percent moisture for percent stand, plant height, or root weight was not significant. There were significant differences among the isolates for the percent stand, root rot rating, and root fresh weight of soybean in each study. In both temperature and moisture studies, the R. solani isolates could be separated as predominantly causing (i) seed rot, as detected by greatly reduced plant stand; (ii) root rot generally having no effect on plant stand but a high root rot rating and low root weight; or (iii) hypocotyl lesions, having no effect on plant stand, a low root rot score, and a high number of red lesions on the hypocotyl. In the greenhouse seed treatment evaluations of five fungicides, there was no fungicide by isolate interaction using these pathogenic types of R. solani. None of the seed treatments evaluated in this study provided 100% control of the four isolates tested. Due to the wide range of environmental factors that permit R. solani infection and disease on soybeans, other control measures that last all season, such as host resistance, should be emphasized.

Effect of seed treatments on emergence, yield, and root rot severity of soybean under Rhizoctonia solani inoculated field conditions in Ontario

“…Likewise, total precipitation for May and June 2002 was 291.1 mm, which was 117.5 and 85.6 mm higher than in 2001 and 2003, respectively. Relatively cool and wet soil conditions are considered favorable for the pathogen, and adversely affect germination and establishment of seedlings by predisposing the plants to infection for a longer period (Dorrance et al 2003). The results of this study support Teo et al (1988), who reported that higher disease incidence at higher soil *, ** Significant at P < 0.05, and P < 0.01 level, respectively; -indicates no data collected.…”

“…Anchor (carbathiin plus thiram) and Vitaflo-280 (carbathiin plus thiram), were the only two seed treatment products available for soybean at the time of this research (OMAFRA 2001). The efficacy of these seed treatments, based on plant emergence or disease incidence, was found to be variable and dependent on disease pressure and environmental conditions (Dorrance et al 2003). There is a lack of scientific results supporting the benefit of these seed treatments in terms of yield under R. solani inoculated field conditions.…”

“…have been used to control rhizoctonia root rot of soybean in the United States [Environmental Protection Agency (EPA) 1999; Dorrance et al 2003;Jardine et al 2003;McLean and Lawrence 1999;Shaner and Buechley 2001]. Of these fungicides, only metalaxyl has systemic activity, but the compound apparently does not move downward into the roots (Worthing 1983).…”

Pepper and Onion Yield Estimate Parameters as Affected by Seed Treatment Options: In the Selected Districts of Central Rift Valley; Oromia Regional State of Ethiopia

“…According to [7] and [8] although not always consistently, fungicide seed treatments have been shown to provide protection to soybean against stand or yield reductions caused by seedling diseases in certain instances.…”

Evaluation of chemical and biological seed treatments to control charcoal rot of soybean

“…Moreover, soybean seeds treated with thiram reduced the incidence of Phomopsis sojae and increased seed germination (Hepperly and Sinclair 1978). In studies on the control of R. solani, Martin et al (1984) demonstrated differences in sensitivity to different fungicides among R. solani isolates, and Dorrance et al (2003) assessed five fungicide seed treatments to control R. solani on soybean in the greenhouse. However, none of the evaluated seed treatments completely controlled the four tested isolates.…”