A Cleaved Amplified Polymorphic Sequence (CAPS) Marker Associated with Root-Knot Nematode Resistance in Sugarbeet

cluding California (Altman and Thomason, 1971; Whitney and Duffus, 1986; Duffus and Ruppel, 1993). Resistance to root-knot nematode (Meloidogyne spp.) previously Disease of sugar beet caused by root-knot nematode was introgressed into sugar beet (Beta vulgaris L.) from wild beet [B. vulgaris ssp. maritima (L.) Arcang] and was demonstrated to be is manifested by galls that form on lateral roots and the dominant and simply inherited. Since resistance conferred by this tap root (Whitney and Duffus, 1986). In warm climates gene was effective against six different Meloidogyne spp. tested, the with long growing seasons, early colonization of young locus was designated R6m-1. An interpollinated progeny population roots can lead to severe crop losses through plant death. of resistant heterozygotes segregating for R6m-1, was exposed to In older beets, nematode infection and galling increase nematodes in a greenhouse and rated for root knot disease symptoms. the possibility of secondary invasion by root pathogens Resistance vs. susceptibility segregated at approximately a 4:1 ratio and is consequent with leaf chlorosis, further supand 120 resistant roots and 48 susceptible roots were chosen for the pressing yield potential. In the absence of genetic resisgeneration of molecular markers linked to the resistance trait. Bulked DNA samples prepared from shoots sprouting from the selected plants tance in commercial varieties, both crop rotation and were subjected to random amplified polymorphic DNA (RAPD) nematicides have been used to manage root-knot nemaanalysis and yielded a marker of 600 base pair (bp) that was highly tode. However, because of nematodes’ wide host range associated with resistance. Sequence analysis of the 600-bp product and increasing restrictions on nematicide use, control led to the design of DNA primers for specific amplification of a 580-bp of Meloidogyne spp. in sugar beet fields continues to product, the generation by polymerase chain reaction (PCR) of which be problematic. occurred in plants both susceptible and resistance to nematode. ComBreeding for resistance to root knot nematode in parison between the sequences generated from resistant plants and sugar beet has been a relatively recent endeavor. Yu susceptible plants revealed numerous nucleotide substitutions. One base substitution associated in repulsion with resistance conditioned (1995) reported the existence of root-knot nematode the existence of a recognition site for cleavage by the restriction resistance in rare strains of B. vulgaris ssp. maritima. endonuclease MseI. Amplification and cleavage of the product with Further investigation resulted in the discovery of an MseI yielded a CAPS marker designated NEM06 that cosegregated isozyme marker associated with a gene for resistance with resistance to the root knot nematode. Computer-assisted translato root-knot nematode in Mi-1 Beta (Yu et al., 2001). tion and comparison with sequences in public databases indicates that By contrast, the sugar beet cyst nematode, Heterodera the marker DNA sequence encodes a protein with high sequence schachtii Schm., has been the subject of intense research similarity to a plant transcription factor. effort, culminating in the positional cloning of the Hs1 gene for resistance to a limited number of races of this organism (e.g., Cai et al., 1997). The difference R nematode causes disease in sugar beet in research effort is due to the fact that infestation of and other crops within the genus Beta. Although sugar beet fields with cyst nematode is more widely nematodes are serious pests of crops worldwide, they spread than root-knot nematode and leads to more seriaffect sugar beet production in comparatively localized ous, recurring losses to growers. growing regions. Nonetheless, in areas where MeloidoMolecular markers have gained favor in plant biology, gyne spp. occur, they can be a serious problem and in including aspects of plant breeding. A molecular marker some cases result in crop failure. Of economical signifimay serve as a guide in determining which plants should cance to sugar beet are the root-knot nematodes M. be advanced within a program for varietal improvement incognita Chitwood, M. arenaria Chitwood, M. javanica (Knapp, 1998). In addition, markers that tag disease Chitwood, M. hapla Chitwood, M. fallax Karssen, and resistance genes can be used to map the locations of M. chitwoodi (Whitney and Duffus, 1986). In the USA, genes in genomes, assess the extent of clustering of such M. incognita and M. javanica cause the greatest sugar genes on chromosomes, and aid in the cloning of genes beet crop losses, primarily in production regions south by map-based strategies (Hammond-Kosack and Jones, of the 40th parallel and in the southwestern USA, in1997). By combining the availability of DNA-based markers with annotated genome sequence data, the loJ.J. Weiland, USDA-ARS, Red River Valley Agricultural Research calization of markers on genome maps promises to be Center, Fargo, ND 58105; M.H. Yu, USDA-ARS, Crop Improvement and Protection Research Laboratory, Salinas, CA 93905. Mention of greatly accelerated. a trademark, vendor, or proprietary product does not constitute a In this report, we sought to obtain molecular markers guarantee or warranty of the product by the USDA and does not linked to nematode resistance present in the M66 Series imply its approval to the exclusion of other products or vendors that of sugar beet described by Yu (1996). A 0.6-kbp RAPD may also be suitable. Received 6 Sept. 2003. *Corresponding author ([email protected]). marker tightly linked with resistance to root-knot nematode was obtained from the study. The characterization Published in Crop Sci. 43:1814–1818 (2003). of this marker and its conversion to a CAPS (Konieczny  Crop Science Society of America 677 S. Segoe Rd., Madison, WI 53711 USA and Ausubel, 1993) marker (NEM06) capable of distin-