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Transmission of resistance to the cyst nematode (Heterodera schachtii Schmidt) in the pedigree of a homozygous resistant sugarbeet (Beta vulgaris L.) was studied with the aid of test parents containing either a red hypocotyl marker or male-sterility. The results indicated that virtually all megaspores and microspores produced from the resistant homozygotes carried resistance to their resultant progeny. However, resistance transmission was less than complete in succeeding generations, being 97.5% through eggs and 95.7% through pollen of the S2 plants of sugarbeet line 3584. These results indicate that nematode resistance may be lost from a homozygous resistant sugarbeet line, although only at a low rate. Therefore, future sugarbeet hybrid cultivars should be developed from an early generation of a resistant homozygote to maintain the highest level of nematode resistance. No close linkage between the loci for hypocotyl color and nematode resistance was detected.
Key Words: Beta vulgaris L. Heterodera schachtii Schmidt Breeding Interspecific hybridization Resistance screening
2 Research geneticist, USDA-ARS-WR, P.O. Box 5098, Salinas, CA 93915.
Received for publication January 10, 1983.
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