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item Brown, Charles - Chuck
item Mojtahedi, Hassan

Submitted to: Genetic Improvement of Solanaceous Crops, Volume 1: Potato
Publication Type: Book / Chapter
Publication Acceptance Date: 8/15/2004
Publication Date: 5/15/2005
Citation: Brown, C.R., Mojtahedi, H. 2005. Breeding for resistance to meloidogyne species and trichodorid-vectored virus. p. 267-292. In M.K. Razdan and A.K. Matto (eds),Genetic Improvement of Solanaceous Crops, Vol I: Potato. Science Publishers, Inc., Enfield, N.H. USA.

Interpretive Summary: Potato production in the Pacific Northwest is plagued by several problems caused by nematodes (microscopic worms) in the soil. Columbia root-knot (CRN) nematode causes deformation of the potato skin and spots in the flesh that ruin the potato for market. Growers address these nematodes by applying soil fumigants. Another nematode, the stubby root nematode, carries a virus that when injected into potatoes caused black spots to develop, which means the potatoes with this blemish (Corky ringspot) cannot be marketed. Growers address these nematodes by applying soil fumigants. Fortunately there are sources of resistance to both of these conditions. Wild potatoes from Mexico have been found to harbor resistance to CRN. Diverse breeding lines of potato have shown resistance to corky ringspot. By making crosses among resistant clones and advanced breeding lines that contribute high yield and processing quality it has been possible to produce promising clones with resistance to one or both of these maladies. New varieties with resistance to either or both of these could potentially save growers hundreds of dollars in fumigation costs, while reducing the load of soil fumigants in the environment, especially in ground water.

Technical Abstract: The increased cultivation of potato in warmer and tropical production areas necessitated a search for resistance to Southern Root Knot Nematode (SRN). No useful resistance among cultivated materials was identified. Extensive surveys of wild species identified a number of resistant candidates. The wild species S. sparsipilum has proven to be a good source that has been introgressed into advanced breeding material. Resistance from S. sparsipilum appeared to be highly heritable. Melodiogyne chitwoodi, Columbia root-knot nematode (CRN) described first in 1980, has come to dominate root-knot research efforts in certain traditional production areas including the Netherlands and the Western United States. Resistance to CRN was not available in cultivated materials, but was found in S. bulbocastanum, S. hougasii, and S. fendleri. Inheritance studies have determined monogenic dominant resistance in both S. bulbocastanum and S. hougasii. The genomic location of resistance in both species has been mapped to homologue 11. In contrast, there are numerous varieties and advanced breeding materials presenting resistance to Tobravirus tobacco rattle virus (TRV) vectored by Trichodorid nematodes. Although apparently not simply inherited, resistance to TRV is heritable enough to be readily bred into progeny of resistant parents. Transgenic resistance to TRV, utilizing a pathogen derived resistance approach has been researched by several groups. Partial levels of resistance have had the undesirable concomitant attributes of being strain-specific or providing resistance to TRV by mechanical inoculation to foliage but not by nematode transmission. Different strategies of transgenic resistance obviously need to be examined. The addition of these combination of these two types of natural resistance germplasm either singly or combined, to new commercial varieties would reduce the burden of soil fumigation that is a particularly heavy cost in the Pacific Northwest of the US.