ARS | Publication request: THE CONCEPT OF MINIMUM ASSURED FREQUENCY OF (CMS)-MAINTAINER ALLELES (M.A.F.M.A.) IN USDA-ARS SUGARBEET GERMPLASM ENHANCEMENT

Submitted to: American Society of Agronomy Meetings
Publication Type: Abstract Only
Publication Acceptance Date: October 21, 1999
Publication Date: N/A

Technical Abstract: Sugarbeet germplasm released up through the 1980's from USDA-ARS had potential for direct use as parents in commercial hybrid cultivars. Monogerm releases were also Type-O (homozygous recessive for the two cytoplasmic male sterility maintainer alleles needed for hybrid seed production), although some were later found to be imperfect Type-O. Type-O Ogermplasm is developed by labor-intensive, calender-consuming identification of individual Type-O plants, found as 1% or less in most populations, by evaluation of testcross progeny. Misindentification of progeny occurs under some situations; a 5 degree C temperature difference gave plentiful pollen (25o) or white anthers (30o). USDA-ARS sugarbeet germplasm releases in the 1990's have been less usable as parental lines, as emphasis shifted to germplasm diversity and combinations of desireable and emerging traits in less finished form. The complete assurance of CMS maintenance provided in Type O releases is expensive for ARS geneticists t create, and is more efficiently created by the commercial seed industry from ARS germplasm released with minimum assured frequencies of Type-O plants, based on pedigree information from use of Type-Os in generating populations for improvement. Traditional EL germplasm has had sucrose percentages too low for easy use by commercial breeders. A program of population creation re- lying on 1978 mm Type-O Beltsville release SP550-0 to provide higher SUC%, Cercospora resistance, and maintainer alleles, to germplasm otherwise high in SR or Rhizoctonia resiatance, is in progress. Hindrances to germplasm mixing such as self-fertility from SP550-0 are being dealt with.