|Brown, Charles - Chuck|
|Yang, Ching Pa|
Submitted to: Journal of Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/19/1995
Publication Date: N/A
Interpretive Summary: Potato production in the Northwest of the USA is plagued with a significant and costly soilborne pest, Columbia root-knot nematode. About three-quarters of the growers in Washington State apply fumigants to control this nematode. On an annual basis, growers spend $20 M to control M. chitwoodi and it is calculated that the crop would be reduced in value by $40 M if soil fumigants were not employed. The best alternative to use of chemical fumigants is to grow resistant potato cultivars. Unfortunately, no resistance was found in cultivated potato. We searched for resistance among wild relatives. We found resistance to this pest of potato in a wild relative that grows in Mexico. During the course of breeding the resistance into advanced potato cultivars, we developed a gene map for the wild species chromosomes. The map permitted us to locate the resistance genes on one arm of chromosome 11 of the wild species. We are using this map and additional markers to accelerate the breeding process for the incorporation of resistance. The development of nematode resistant potato cultivars will permit potato growers to reduce the use of soil fumigants which will lower the cost of production, reduce risk of nematode damage to their crop, and decrease pollution of the groundwater.
Technical Abstract: The mapping of resistance to Meloidogyne chitwoodi derived from Solanum bulbocastanum is reported. A somatic hybrid of nematode resistant S. bulbocastanum and cultivated tetraploid potato was produced. This was backcrossed to tetraploid potato, and a single resistant BC1 was selected and backcrossed again to the same recurrent tetraploid parent. The mapping population consisted of 64 BC2 progeny scored for restriction fragment length polymorphic (RFLP) markers and 62 of these were evaluated for reproductive efficiency of race 1 of M. chitwoodi. Forty-eight polymorphic RFLP markers, originally derived from tomato and mapped in diploid cultivated potato, were assigned to 12 chromosomes of S. bulbocastanum. Of the 62 progeny screened for nematode resistance, 18 were non-hosts and 4 poor hosts. The rest were highly susceptible (good hosts). Analysis of the resistance (including non-hosts and poor hosts) as both a qualitative trait and as a meristic trait on which QTL analysis was applied supported the same genetic hypothesis. Genetic control was localized solely to factor(s) lying at one end of chromosome 11. The level of expression of resistance in the S. bulbocastanum parent and the resistant portion of the BC2 was essentially equal. This fact and the highly significant LOD scores for one end of the chromosome 11 marker array support a genetic model equivalent to monogenic dominant control.