REVIEW ARTICLE AGBIR Vol.37 No.1 January-2021 1 Department of Plant Pathology, North Dakota State University, Fargo, North Dakota 58108, USA; 2 Department of Plant Pathology, University of North Dakota, Grand Forks 58202, USA; 3 Bangladesh Agricultural Research Institute, Joydebpur, Gazipur-1701, Bangladesh; 4 Gottfried Wilhelm Leibniz Universität Hannover, Germany. Correspondence: Haque ME, Department of Plant Pathology, North Dakota State University, Fargo, North Dakota 58108, USA, E-mail: mdehsanul.haque@ndus.edu Received: December 21, 2020, Accepted: January 04, 2021, Published: January 11, 2021 This open-access article is distributed under the terms of the Creative Commons Attribution Non-Commercial License (CC BY-NC) (http:// creativecommons.org/licenses/by-nc/4.0/), which permits reuse, distribution and reproduction of the article, provided that the original work is properly cited and the reuse is restricted to noncommercial purposes. For commercial reuse, contact reprints@pulsus.com 96 Sugar beet, it ‘disease rhizoctonia root rot, and potental biological agents Haque ME 1,2* , Parvin MS 3,4 routinely followed to reduce the pathogen propagules. Alternatively, biocontrol strategies are environmentally safe, generally pose little risk of developing resistant biotypes, nevertheless, there has not been much success achieved in controlling R. solani in sugar beet with biocontrol agents in the field. This review article discussed the traditional management strategies and potential biological agents of Rhizoctonia solani. Key Words: Sugar beet; Rhizoctonia solani; Rhizoctonia root Haque ME, Parvin MS. Sugar beet, it ‘disease rhizoctonia root rot, and potential biological agents. AGBIR. 2021;37(1):96-101. Sugar beet (Beta vulgaris L.) is supplying approximately 35% of sugar worldwide. Rhizoctonia root rots in sugar beet is a setback for commercial cultivation. Disease severity increases when the weather is warm and under wet field conditions. Generally, integrated disease management strategies that involves cultural practice, chemical control, and host resistance are SUGAR BEET DOMESTICATION AND US COMMERCIALIZATION Sugar beet is an economically important crop of the large order Caryophyllales, supplying approximately 25% of sugar worldwide [1]. The sugar beet genome is diploid with 2n=18 chromosomes and the estimated genome size is 731 Mbp (megabases/millions of base pairs) [2]. The sugar beet wild ancestors are the sea beet (Beta vulgaris subsp. maritima) which resides in the family, Amaranthaceae and sub-family, Betoideae [3,4] (Figures 1 and 2). About 1500 years ago, sugar beet was introduced to China from Arabia. As it had high economic value in many countries, improvement of the crop has been extensively explored. It is a biennial crop with a sugar-rich tap root in the first year and a flowering seed stalk in the second. Currently, the crop is cultivated mainly in temperate regions between 30° and 60° N from Cairo to Helsinki [5,6]. In the USA, sugar beet production was done in 1838 in Northampton, MA, and the first successful sugar factory was set up in 1879, in Alvarado, CA, [7]. Sugar beet provides about 55% of the total sugar produced domestically, while sugar cane contributes 45% [8,9]. Sugar beet is currently grown in 11 states of the USA which includes Minnesota, Idaho, North Dakota, Michigan, Nebraska, Montana, California, Wyoming, Colorado, Oregon, and Washington. Sugar beet thrives well in temperate climatic conditions but can also be produced in warm climates. The Red River Valley (RRV) of western Minnesota and eastern North Dakota is the largest area of producers of sugar beet in the United States. The first sugar beet factory was established in the RRV in 1926 in East Grand Forks [10]. Currently, there are three sugar beet cooperatives in the RRV: American Crystal Sugar Company, Minn-Dak Farmers’ Cooperative, and Southern Minnesota Beet Sugar Cooperative are located in Minnesota and North Dakota. These sugar beet cooperatives contribute approximately 57% of the US sugar beet acreage. This has created a huge economic impact of over $5 billion in the Upper Midwest. In USA, the total sugar beet planted area and yield was 1,132,000 acres and 28,600,000 tons, respectively in 2019. Since the mid-1970s growers in the US started joining together as farm- owned cooperatives, purchased the processing companies and managed the marketing and sales of their production. In the USA, private companies own the commercial seed production and the variety improvement programs. The USDA helps to select and improve germplasm before making lines available to the seed companies for further development and commercialization. The varieties today are relatively high yielding and are moderately resistant to most of the common soil borne and foliar pathogens. For example, most varieties must have a minimum level of resistance to root pathogens such as Rhizoctonia, Aphanomyces, Pythium, Fusarium, sugar beet cyst nematode and viruses such as Beet Necrotic Yellow Vein and Curly Top [8,11,12]. Thus, the commercialization of sugar beet advanced with the establishment of sugar processing houses and increased in efficiency in the field and factory. Improved seed and varietal choice have made commercialization easier as it has helped farmers choose the best varieties for better yield and quality [13,14]. However, several diseases are major limiting factors to sugar beet yield potential. Cercospora leaf spot is one of the most important and widespread foliar diseases in sugar beet. It is caused by a hemibiotrophic filamentous fungal pathogen, Cercospora beticola, which causes necrotic lesions and progressive destruction of the plant’s foliage [6]. Research has been ongoing Figure 1) Position of Amaranthaceae family under the order of Caryophyllales. Figure 2) A flow chart showing evolutionary affinities of Beta vulgaris, modified sketch of Ford-Lloyd and William (1975).