36th International Carrot Conference Abstract

IDENTIFYING NEW GENES FOR MELOIDOGYNE INCOGNITA NEMATODE RESISTANCE IN CARROT

*Joshua D. Parsons¹, William C. Matthews², Philip A. Roberts², Philipp W. Simon^1,3

^1. University of Wisconsin-Madison Department of Horticulture

^2. University of California-Riverside Department of Nematology

^3. USDA-ARS, Vegetable Crops Unit

Root knot nematodes (Meloidogyne spp.) are a major pest attacking carrots (Daucus carota) worldwide, causing galling and forking of the carrot root, and rendering them unacceptable for market. The current management practices of applying broad spectrum nematicides is effective, but is coming under more restrictive regulations, is costly for growers, and is considered damaging to the environment. Genetic resistance to nematodes could eliminate or strongly reduce the use of broad spectrum soil fumigants in carrot production. Resistance to M. javanica has already been discovered in a Brasilian cultivar and mapped to the Mj-1 locus on chromosome 8. Genetic resistance to M. incognita has been observed but previously unmapped. Three diverse sources of resistance, from Syria (HM), Europe (SFF) and South America (B1091) have been identified. Two F₂ mapping populations were developed using these parents, (B1091 x HM1) and (SFF x HM2), as well as a segregating population developed by self pollinating a single carrot from an open pollinated cultivar of HM (HM3). Plants of all three populations were grown individually in pots in a greenhouse, inoculated with M. incognita, and evaluated for their resistance to infection. DNA samples were collected and evaluated with AFLP fingerprinting, SSRs, and SNPs. QTL analysis using r/qtl revealed 5 qtl for B1091 x HM1, 6 for SFF x HM2, and 3 for HM3 (using a significance threshold of 0.1 on 1,000 permutations for each population individually). A consensus map was developed using JoinMap and the qtl regions were compared between populations. One qtl was present in all 3 populations, in the same region on chromosome 8 as Mj-1. There were also 2 other qtl regions shared between B1091 x HM1 and SFF x HM2. F₃ progeny from the F₂ mapping populations have been phenotyped and are being genotyped to confirm and refine mapping of the qtl regions.

Last updated Friday, 02-Aug-2013 12:12:34 CDT