36th International Carrot Conference Abstract

Root-Knot Nematode Resistance in Carrot: a Focus for Breeding

Philip A. Roberts¹, Philipp W. Simon², William C. Matthews Jr.¹, Joe Nunez³

¹ Department of Nematology, University of California, Riverside, CA 92521

² USDA-ARS, Vegetable Crops Unit, Dept. of Horticulture, University of Wisconsin-Madison,1575 Linden Drive, Madison, WI 53706

³ Vegetable/Plant Pathology Advisor, UC Cooperative Extension, 1031 South Mount Vernon Avenue, Bakersfield, CA 93307

Several species of root-knot nematodes are severely damaging to carrots, among which Meloidogyne javanica and M. incognita are major parasites in many warm climate areas worldwide. Their damage potential and the economic loss of marketable yield in carrot is high relative to most crops because low infestation levels in carrot fields cause significant ‘cosmetic injury’ by galling and forking disfiguration of the taproot. Fresh market carrot production is heavily reliant on pre-plant nematicide treatments of infested fields, and development of resistant carrot varieties will provide alternative nematode management options to carrot growers. We have been examining and selecting resistance sources in multiple carrot backgrounds, with the goal of breeding varieties with resistance to both root-knot nematode species. Species identification is difficult and growers typically are lacking species level identity of their root-knot infestations. For effective management, having carrot varieties resistant to both species is important. While the ‘Brasilia’ source provided the Mj-1 gene for strong resistance to M. javanica, its effects on M. incognita have appeared variable. Many lines developed from Brasilia x USDA inbred lines also show good resistance to M. incognita, but others have weaker resistance. Recently we produced a population fixed for Mj-1 but fully segregating for M. incognita resistance, indicating that one or more additional genes are important for achieving the full resistance complement in the Brasilia-derived lines. In addition, multiple other resistance sources from Homs, Ping Ding, and other backgrounds provide opportunity to broaden the nematode resistance base in elite carrot varieties. The management potential of resistance will be discussed with respect to multiple root-knot nematode species.

Last updated Thursday, 25-Jul-2013 12:47:55 CDT