INVESTIGATION Genetic Mapping of Resistance to Meloidogyne arenaria in Arachis stenosperma: A New Source of Nematode Resistance for Peanut Soraya C. M. Leal-Bertioli,* ,†,1,2 Márcio C. Moretzsohn,* Philip A. Roberts, ‡ Carolina Ballén-Taborda, † Tereza C. O. Borba, § Paula A. Valdisser, § Rosana P. Vianello, § Ana Cláudia G Araújo,* Patricia M. Guimarães,* and David J. Bertioli †, ** *Embrapa Genetic Resources and Biotechnology, PqEB W5 Norte Final, Brasília, DF, 70770-917, Brazil, † Center for Applied Genetic Technologies, University of Georgia, Athens, Georgia 30602-6810, ‡ Department of Nematology, University of California, Riverside, California 92521, § Embrapa Rice and Beans, Rodovia GO-462, km 12 Zona Rural C.P. 179, Santo Antônio de Goiás, GO, 75375-000, Brazil, and **University of Brasília, Institute of Biological Sciences, Campus Darcy Ribeiro, Brasília, DF, 70910-900, Brazil ABSTRACT Root-knot nematodes (RKN; Meloidogyne sp.) are a major threat to crops in tropical and subtropical regions worldwide. The use of resistant crop varieties is the preferred method of control because nematicides are expensive, and hazardous to humans and the environment. Peanut (Arachis hypogaea) is infected by four species of RKN, the most damaging being M. arenaria, and commercial cultivars rely on a single source of resistance. In this study, we genetically characterize RKN resistance of the wild Arachis species A. stenosperma using a population of 93 recombinant inbred lines developed from a cross between A. duranensis and A. stenosperma. Four quantitative trait loci (QTL) located on linkage groups 02, 04, and 09 strongly influenced nematode root galling and egg production. Drought-related, domestication and agronomically relevant traits were also evaluated, revealing several QTL. Using the newly available Arachis genome sequence, easy-to-use KASP (kompetitive allele specific PCR) markers linked to the newly identified RKN resistance loci were developed and validated in a tetraploid context. Therefore, we consider that A. stenosperma has high potential as a new source of RKN resistance in peanut breeding programs. KEYWORDS Arachis peanut QTL root-knot nematode resistance marker-assisted selection drought yield introgression Nematodes of the genus Meloidogyne, or root-knot nematodes (RKN) cause significant economic losses in agricultural crops worldwide. RKNs are sedentary obligate plant endoparasites, and, as a result of nematode feeding, large galls or “knots” are formed throughout the root system of infected plants. Severe infections reduce yields in numerous crops and can also affect consumer acceptance of many plants, espe- cially vegetables. RKNs establish a complex biotrophic relationship with their hosts. Second-stage juveniles invade root tip cells, migrate through the root cortex, and, after electing suitable root cells, induce redifferentiation into specialized feeding cells. Feeding cells enlarge and are converted into multinucleate giant cells through synchronous nu- clear divisions without cell division. Hyperplasia and hypertrophy of the surrounding cortical cells lead to the formation of the typical root gall, the primary visible symptom of infection. Plant nutrient and water uptake is substantially reduced by the resulting damage to the root system, and infested plants are therefore weak and low yielding (Caillaud et al. 2008). Management of nematodes typically in- cludes use of chemicals, crop rotation, and use of resistant culti- vars. Most chemical control agents against RKNs have been prohibited for environmental and health reasons (De Waele et al. 1989), and crop rotation is limited because of the wide range of Copyright © 2016 Leal-Bertioli et al. doi: 10.1534/g3.115.023044 Manuscript received September 29, 2015; accepted for publication November 30, 2015; published Early Online December 10, 2016. This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/ licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Supporting information is available online at www.g3journal.org/lookup/suppl/ doi:10.1534/g3.115.023044/-/DC1 1 Corresponding author: Embrapa Genetic Resources and Biotechnology, PqEB W5 Norte Final, Brasília, DF, 70770-917, Brazil. E-mail: soraya.bertioli@embrapa.br 2 Present address: Center for Applied Genetic Technologies, University of Georgia, 111 Riverbend Road, Athens, GA, 30602-6810 Volume 6 | February 2016 | 377