Submitted to: Journal of Sugarbeet Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2007
Publication Date: 6/10/2008
Citation: Metzger, M.S., Weiland, J.J. 2008. Growth Promotion May Compensate for Losses Due to Moderate Aphanomyces Root Rot. Journal of Sugarbeet Research. 45:1-17.
Interpretive Summary: Root rot diseases of sugarbeet cause perennial losses to the crop in the US. In 2001 and 2002, field and controlled environment trials using environmentally-friendly methods to control one cause of root rot, that caused by the fungus Aphanomyces cochlioides, were undertaken. Biocontrol bacteria, beneficial to the sugarbeet plant, were applied to the seed before planting in fields known to have high potential for root rot disease. Additional treatments included the industry-standard seed treatement with the product TachigarenTM and a test of induced resistance natural resistance with the commercial product MessengerTM applied as a foliar spray. The biocontrol bacteria exhibited poor control of root rot disease in these trials, whereas the MessengerTM treatments indicated potential use of this product or this approach in the supplementing current measures for controlling Aphanomyces root rot disease. The results of the study and the literature cited therein indicate that biological control of this disease may provide a useful partner along with chemical fungicide(s) and genetic resistance.
Technical Abstract: A two-year study was conducted to investigate the use of chemically-induced resistance and biocontrol bacteria for reducing sugar beet root rot disease caused by the oomycete organism Aphanomyces cochlioides. Stand establishment, yield, and quality analysis of sugarbeets from replicated field plots, as well as root rot of seedlings grown in controlled conditions, were analyzed. Bacterial isolates AMMDR1 of Burkholderia cepia and PRA25rifz of Pseudomonas fluorescens were tested for the ability to inhibit reductions in stand and yield caused by A. cochlioides. A commercially available inducer of systemic resistance (harpin protein formulated as MessengerTM) was also tested in the field for the ability to reduce root rot disease, whereas the inducers harpin, salicylic acid, and riboflavin were tested in growth-chamber studies. Field and growth chamber data combined suggested that a subset of the biological treatments in combination with chemical treatments enhanced root yield and recoverable sugar over control treatments even when stand and root rot ratings were unimproved. Integration of induced resistance and biocontrol with cultural practices, chemical treatments, and heritable resistance may lead to improved control of Aphanomyces diseases of sugarbeets.