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Title: OBJECTIVES OF SUGAR BEET BREEDING, RESISTANCE TO PARASITES, FUNGI, ROOT ROTS.

Author
item Panella, Leonard

Submitted to: Genetics and Breeding of Sugar Beet
Publication Type: Book / Chapter
Publication Acceptance Date: 12/15/2003
Publication Date: 5/1/2005
Citation: Panella, L.W. 2005. Objectives of sugar beet breeding, Resistance to Parasites, Fungi, Root rots. pp. 95-100. In (eds. E. Biancardi, L. G. Campbell, G.N. Skaracis, & M. De Biaggi) Genetics and Breeding of Sugar Beet. Science Publishers, Inc. Enfield (NH), USA. 2005 (Book Chapter).

Interpretive Summary: Rhizoctonia root rot is endemic in all sugar beet production areas and causes root- and crown-rot and seedling damping-off. Pythium can harm sugar beet seedlings (damping-off) or cause a root and tip rot in the mature root. Phoma root rot can cause a seedling disease (damping-off), a mature root rot, often reffed to as blackleg and a post harvest rot of roots beets in storage piles. The seedling damping-off and storage rot are the most damaging diseases caused by Phoma. The seedling damping-off is controlled by chemical seed treatments, and, although there have been some attempts to develop resistant germplasm, this is not a major breeding goal for commercial seed companies. John Gaskill began a Rhizoctonia root- and crown rot resistance breeding program in the late 1950s at the USDA-ARS research station in Fort Collins, Colorado. Gaskill realized that in a natural there was not consistent, uniform disease pressure and so he developed the method of creating an artificial epidemic of Rhizoctonia in the field. He released the first two resistant line in 1966 and releases of resistant sugarbeet from this program have continued ever since. There have been continued efforts to screen new sources of resistance for over 40 years nonetheless, most commercial resistant germplasm can trace its parentage to the USDA-ARS program in Fort Collins, Colorado. Today, Rhizoctonia resistance has been incorporated by major seed companies into commercial hybrids. Working at the USDA-ARS Research Station in Fargo, North Dakota (ND), Bill Bugbee utilized methods for selecting individual roots resistant to Phoma and other diseases causing storage rot, and demonstrated that protection offered by resistant lines was comparable to that from fungicide application. Five germplasm with resistance to storage rot have been released from the USDA-ARS in Fargo, ND. Although Pythium is known to cause seedling damping off, it can also cause a root rot in the mature beet root, and Pythium is commonly found with other disease root rot complex of diseases. There has been very little effort in breeding for resistance until recently, when the Europeans evaluated 597 sources for seedling resistance to Pythium.

Technical Abstract: Rhizoctonia solani Kuehn is endemic in all sugar beet production areas and causes root- and crown-rot (AG-2-2) and seedling damping-off (primarily AG-4). Pythium spp., Pythium aphanidermatum (Edson) Fitzp., Pythium deliense Meurs., and Pythium ultimum can harm sugar beet seedlings (damping-off) or cause a root and tip rot in the mature root. Phoma betae Frank can cause a seedling disease (damping-off), a mature root rot, often reffed to as lackleg and a post harvest rot of roots beets in storage piles. The seedling damping-off and storage rot are the most damaging diseases caused by P. betae. The seedling damping-off caused by these pathogens generally is controlled by chemical seed treatments, and, although there have been some attempts to develop resistant germplasm, this is not a major breeding goal for commercial seed companies. John Gaskill began a Rhizoctonia root- and crown rot resistance breeding program in the late 1950s at the USDA-ARS research station in Fort Collins, Colorado. Gaskill realized that natural field epiphytotic did not produce consistent, uniform disease pressure and he and others used mass selection or recurrent field selection under artificially induced epiphytotics, a method used by many breeding companies today. He released the first two resistant cultivars in 1966 and releases of resistant germplasm from this program have continued ever since. There have been continued efforts to screen genetic resources for new sources of resistance for over 40 years nonetheless, most commercial resistant germplasm can trace its parentage to the USDA-ARS program in Fort Collins, Colorado. Today, resistance to Rhizoctonia has been incorporated by major seed companies into O-type maintainer, CMS female, and multigerm-pollinator lines and is currently being deployed in commercial hybrids combined with Rhizomania resistance. Working at the USDA-ARS Research Station in Fargo, North Dakota (ND), Bill Bugbee utilized methods for selecting individual roots resistant to Phoma betae Frank and other fungi causing storage rot, and demonstrated that protection offered by genetic resistance was comparable to that from fungicide application. Five germplasm with resistance to storage rot have been released from the USDA-ARS in Fargo, ND. Although Pythium spp. are known to cause seedling damping off, they can also cause a root rot in the mature beet root, and Pythium spp. are commonly found with other pathogenic fungi in a oot rot complex of diseases. There has been very little effort in breeding for resistance until recently, when the EC/GRP collaborative project GENRES CT95 42 evaluated 597 accessions from a synthetic core collection for seedling resistance to Pythium ultimum.