Abstract
Rotation crops and biocontrol amendments were investigated for suppression of Rhizoctonia solani on potato (Solanum tuberosum) and their interactive effects on soil microbial communities. Greenhouse trials were conducted to evaluate selected rotation crops, including barley, common and “Lemtal” ryegrass, clover, potato, and combinations of barley with ryegrass or clover, for their effects on populations of R. solani and Rhizoctonia disease. Potato and clover preceding potato resulted in higher disease severity than most other rotations, whereas ryegrass reduced stem canker severity. In addition, all ryegrass treatments resulted in substantially higher populations of R. zeae. Field trials evaluating selected biocontrol treatments in combination with different rotations were conducted at two locations in Maine. Potatoes were treated with the biocontrol organisms Laetisaria arvalis, Trichoderma virens, or Bacillus subtilis and planted following rotation crops of barley and ryegrass, barley and clover, or potato. The barley/ryegrass rotation significantly reduced incidence and severity of stem canker and increased tuber yield at one location. Efficacy of the biocontrol treatments varied by rotation and location, with L. arvalis and T. virens reducing black scurf in some rotations and increasing some aspects of tuber yield at one location. Soil microbial community characteristics differed among rotation crops and biocontrol treatments. Significant crop by biocontrol interactions were observed demonstrating the complex interactions among rotation crops, biocontrol treatments, and soil microbial communities, as well as indicating that biocontrol can be enhanced within beneficial rotations.
Highlights
Rhizoctonia solani Kühn is a persistent pathogen of potato (Solanum tuberosum L.) that causes stem and stolon canker and is responsible for black scurf, a tuber disease caused by the formation of sclerotia, the long-term survival structures of the pathogen, on newly formed tubers [1,2,3,4]
The effects of different rotation crops on soil populations of R. solani and Rhizoctonia disease of potato were examined under controlled conditions in two greenhouse experiments
This research demonstrated the potential benefits of replacing clover as a cover crop in barley rotations with ryegrass, for better control of Rhizoctonia disease and improved potato yield
Summary
Rhizoctonia solani Kühn is a persistent pathogen of potato (Solanum tuberosum L.) that causes stem and stolon canker and is responsible for black scurf, a tuber disease caused by the formation of sclerotia, the long-term survival structures of the pathogen, on newly formed tubers [1,2,3,4]. These symptoms result in reduced tuber quality and yield. Previous research in potato systems has demonstrated that each type of rotation crop produces distinctive changes in soil microbial community characteristics, as well as that these characteristics may be related to disease characteristics [6,11,12]
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