|MADDOX, ANN MARIE - California State University|
|HUTMACHER, ROBERT - University Of California|
|ELLIS, MARGARET - University Of California|
Submitted to: APS Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 7/17/2020
Publication Date: 8/3/2020
Citation: Maddox, A., Hutmacher, R.B., Ulloa, M., Ellis, M.L. 2020. The effects of pH and temperature on growth of Rhizoctonia solani isolated from symptomatic cotton using in vitro assays. APS Annual Meeting - Plant Health Conference. Denver, CO, USA. August 10-14, 2020. 17396.
Technical Abstract: Rhizoctonia solani is a common soilborne pathogen that causes seedling disease in cotton. Seedling disease caused by R. solani in cotton has been found to be most prevalent in sandy acidic soils, and under cool and wet conditions. However, R. solani has also been found causing disease in heavier alkaline soils in California. Therefore, this study evaluated the effect of pH and temperature in an in vitro assay using two R. solani isolates collected from cotton. Each isolate was evaluated on an artificial culture medium at six pH levels (4, 5, 6 ,7 ,8, 9) and incubated at four temperatures (15, 20, 25, 30°C). There were three replicate plates per treatment combination and the experiment was repeated. Data for average colony diameter for each plate was taken at 72 h. There was a significant difference for pH and temperature (P <0.0001), but not for isolate. The two R. solani isolates were found to grow best at a lower pH of 4 and 5 with colony dimeters averages for pH at 5.9 cm and 5.8 cm, respectively. The isolates did not grow at the higher pH levels of 8 and 9. For temperature, the most growth occurred at 30°C with an average colony diameter of 5.4 cm, while the least amount of growth was observed at 15°C with an average colony diameter of 1.5 cm. These results, do not support the observation of disease development in cotton caused by R. solani in more alkaline soils, suggesting other factors may be contributing to the success of disease development in these soils. Future greenhouse studies will be used to examine the effect of soil texture and pH on disease development in cotton.