Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/13/2002
Publication Date: 9/20/2003
Citation: WEILAND, J.J., YU, M.H. A CLEAVED AMPLIFIED POLYMORPHIC SEQUENCE (CAPS) MARKER ASSOCIATED WITH ROOT-KNOT NEMATODE IN SUGAR BEET. CROP SCIENCE. 2003. v. 43. p. 1814-1818. Interpretive Summary: Plant breeding programs and our understanding of the genetic basis for disease resistance is enhanced by the availability of molecular markers for such genes. A marker of this kind was discovered for a gene that provides resistance in sugarbeet to a nematode that causes a root malformation in the crop. The marker exploits polymerase chain reaction technology, now available to many research and diagnostic labs around the country. Using a simple one-day test, plant breeders will be able to determine whether the variety that they are breeding has the gene for resistance to this pest. The test will save plant breeders time and resources in the incorporation of this resistance into new sugarbeet hybrids.
Technical Abstract: Resistance to root-knot nematode (Meloidogyne spp.) was introgressed into sugarbeet (Beta vulgaris L.) from wild beet [B. vulgaris ssp. maritima (L.) Arcang] and was demonstrated to be dominant and simply inherited. Since resistance conferred by this gene was effective against six different species of Meloidogyne spp. tested, the locus was designated R6m-1 for resistance to 6 species of Meloidogyne spp. Sugarbeet population 1568, an inter-pollinated progeny population of resistant heterozygotes segregating for R6m-1, was inoculated with J2 nematodes and rated for root knot disease in a greenhouse. Resistance vs. susceptibility segregated at approximately 4:1 ratio, and 120 of the resistant roots and 48 of the susceptible roots were chosen for the generation of molecular marker linked to the resistance trait. Bulked DNA samples prepared from shoots sprouting from the selected plants were subjected to RAPD analysis, yielding a marker of 600 bp that was highly associated with resistance. Sequence comparison between the product generated from resistant plants and susceptible plants revealed numerous nucleotide substitutions. One base substitution associated in repulsion with resistance conditioned the existence of a recognition site for cleavage by the restriction endonuclease Mse 1. Amplification and cleavage of the product with Mse 1 yielded a cleaved amplified polymorphic sequence (CAPS) marker designated Nem06 that segregated 100% with resistance to the root knot nematode.