2018 ASHS Annual Conference

Rhizoctonia solani is a fungal pathogen affecting many crop families. Anastomosis groups (AG) IIIB and IV affect table beet (Beta vulgaris subsp. vulgaris) and Rhizoctonia infections can cause severe yield losses. Resistance to this fungus is available in sugar beet lines, but has yet to be explored thoroughly in table beet. Table beet is an important crop in the state of Wisconsin with over 3,500 acres grown annually for processing.

In the fall of 2016 and spring of 2017 greenhouse screening techniques for Rhizoctonia in table beet were developed. Ten genotypes were screened: three open-pollinated cultivars, three hybrids, two publicly-available inbred lines, and resistant and susceptible sugar beet breeding lines (obtained from the USDA sugar beet breeding program, Ft. Collins, CO). Detroit Dark Red, Red Ace, Camaro, and W364 performed comparably to the resistant sugar beet (mean disease rating= 1.04) with mean disease ratings of 1.69, 1.47, 1.20, and 1.35, respectively. In the spring of 2018, two screens were conducted. The first evaluated 94 PI accessions obtained from the USDA-NPGS in Pullman, Washington. The second evaluated over fifty commercially available cultivars and publicly-available inbred lines. Resistant and susceptible sugar beet breeding lines and one inbred line were included as checks. Each screen was replicated over time. Plants were artificially inoculated at 8 weeks after planting. At 3 and 5 weeks post-inoculation, roots were given a disease score based on their internal and external characteristics. The results from these screens and future screens will be useful in identifying sources of resistance within Beta vulgaris which can be used in breeding for resistance to Rhizoctonia. The research described in this study will be helpful in developing table beet lines with resistance to R. solani.