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Inheritance of Powdery Mildew Resistance in Sugar Beet Derived from Beta vulgaris subsp. maritima

June 2001 , Volume 85 , Number  6
Pages  627 - 631

R. T. Lewellen and J. K. Schrandt , USDA-ARS, U.S. Agricultural Research Station, 1636 E. Alisal St., Salinas, CA 93905

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Accepted for publication 16 February 2001.

Powdery mildew of sugar beet (Beta vulgaris), caused by Erysiphe polygoni, was introduced into North American in 1974. Since then, chemical control has been needed. Moderate resistance of a slow-mildewing type is known and has been used commercially. High resistance was identified recently in B. vulgaris subsp. maritima accessions WB97 and WB242 and has been backcrossed into sugar beet breeding lines. These enhanced lines were used as sources of powdery mildew resistance to determine the inheritance of resistance. Analyses of segregating testcross families showed that resistance from both sources is inherited as a single, dominant, major gene. The gene symbol Pm is proposed for the resistant allele. The allelism of the resistance from the two wild beet sources was not determined. Pm conditions a high level of resistance, but disease developed on matured leaves late in the season. This late development of mildew on lines and the slow-mildewing trait in susceptible, recurrent lines tended to obfuscate discrete disease ratings.

Additional keywords: beet, Erysiphe betae, germ plasm enhancement, prebreeding

The American Phytopathological Society, 2001