HORTSCIENCE, V OL. 38(7), December 2003 1394 PEST MANAGEMENT Response of Bell Pepper Cultivars Near-isogenic for the N Gene to Meloidogyne incognita in Field Trials Judy A. Thies 1 and Richard L. Fery 2 U.S. Vegetable Laboratory, U.S. Department of Agriculture, Agricultural Research Service, 2700 Savannah Highway, Charleston, SC 29414-5334 John D. Mueller 3 , Gilbert Miller 4 , and Joseph Varne 5 Clemson University, Edisto Research and Education Center, 64 Research Road, Blackville, SC 29817 Additional index words. Capsicum annuum var. annuum, Meloidogyne incognita race 3, nematode resistance Abstract. Resistance of two sets of bell pepper [(Capsicum annuum L. var. annuum (Gros- sum Group)] cultivars near-isogenic for the N gene that conditions resistance to root-knot nematodes [Meloidogyne incognita (Chitwood) Kofoid and White, M. arenaria (Neal) Chitwood races 1 and 2, and M. javanica (Treub) Chitwood] was evaluated in field tests at Blackville, S.C. and Charleston, S.C. The isogenic bell pepper sets were ‘Charleston Belle (NN) and ‘Keystone Resistant Giant (nn), and ‘Carolina Wonder (NN) and ‘Yolo Wonder B (nn). The resistant cultivars Charleston Belle and Carolina Wonder were highly resistant; root galling was minimal for both cultivars at both test sites. The sus- ceptible cultivars Keystone Resistant Giant and Yolo Wonder B were highly susceptible; root galling was severe at both test sites. ‘Charleston Belle had 96.9% fewer eggs per g fresh root than ‘Keystone Resistant Giant , and ‘Carolina Wonder had 98.3% fewer eggs per g fresh root than ‘Yolo Wonder B (averaged over both test sites). ‘Charleston Belle and ‘Carolina Wonder exhibited a high level of resistance in field studies at both sites. These results demonstrate that resistance conferred by the N gene for root-knot nematode resistance is effective in field-planted bell pepper. Root-knot nematode resistant bell pep- pers should provide economical and environmentally compatible alternatives to methyl bromide and other nematicides for managing M. incognita. The southern root-knot nematode, Meloidogyne incognita (Chitwood) Kofoid and White, is a major limiting factor to bell pepper (Capsicum annuum L. var. annuum) production in the United States and world- wide (Di Vito et al., 1985, 1992; Sasser and Freckman, 1987; Thies et al., 1997). In the United States, methyl bromide is currently the primary method for controlling root-knot nematodes in bell peppers and accounts for 12% of methyl bromide used for pre-plant fumigation of all crops in the country [U.S. Department of Agriculture (USDA), 1993]. However, because of the ozone-depleting properties of methyl bromide, its production in the United States is scheduled to cease by 1 Jan 2005. Although other soil fumigants and near-isogenic sets of bell pepper cultivars to evaluate the effectiveness of the N gene in M. incognita-infested fields. Materials and Methods These field studies were conducted at the U.S. Vegetable Laboratory, USDA, ARS, Charleston, S.C., and the Clemson Univ. Ed- isto Research and Education Center, Blackville, S.C. Egg inocula of M. incognita race 3 for all experiments was maintained on ‘Rutgers tomato (Lycopersicon esculentum Mill.) and ‘Kentucky Wonder 191 pole bean (Phaseolus vulgaris L.) in isolated greenhouse benches. Meloidogyne incognita egg inocula were ex- tracted from infected tomato and bean roots using 0.5% NaOCl (Hussey and Barker, 1973). Pepper genotypes used in these studies were two sets of near-isogenic bell pepper cultivars that differ for resistance to root-knot nematodes conditioned by the N gene. The bell pepper genotypes used in all experiments were Isogenic Set I: ‘Charleston Belle (NN) and ‘Keystone Resistant Giant (nn) and Isogenic Set II: ‘Carolina Wonder (NN) and ‘Yolo Wonder B (nn). ‘Keystone Resistant Giant and ‘Yolo Wonder B are the susceptible recurrent parental cultivars used in the backcross breeding proce- dure (six backcrosses) to develop ‘Charleston Belle and ‘Carolina Wonder , respectively (Fery et al., 1998). Blackville study. The seeds of all of the entries were planted in the greenhouse on 30 Mar. 2001 in 25 × 51 × 4.5-cm-deep plastic flats containing MetroMix 360 (The Scotts Co., Marysville, Ohio) growing medium. Ten days later, seedlings were transplanted into plastic growing trays containing 50 individual 0.2-L plastic cells (Growing Systems, Milwaukee) filled with MetroMix 360. On 2 May 2001, the field was tilled, beds were formed, and covered with 3-mL black plastic. On 9 May 2001, the pepper seedlings were inoculated with 5000 M. incognita race 3 eggs per seedling, and on 10 May 2001, the seedlings were transplanted into single-row plots on beds 2-m apart. Each plot contained 20 plants spaced 30-cm apart. The experimental design was a randomized complete block with 10 replications. At planting, ten cores of soil were collected from each plot. Second-stage juveniles (J2) were extracted from 400 cm 3 soil using the centrifugal flotation method (Jenkins, 1964). Standard cultural and insect control practices were followed and plots were irrigated with drip irrigation. Fruits were harvested weekly from 28 July through 9 Aug. 2001. On 15 Aug. 2001, the root systems of 10 plants in the center of each plot were dug, roots were washed and rated for gall severity and egg mass production using a scale of 1 to 5, where 1 = 0% to 3% root system galled or covered with egg masses; 2 = 4% to 25%, 3 = 26% to 50%, 4 = 51% to 79%, and 5 = 80% root system galled or covered with egg masses (Thies et al., 1998). Meloidogyne incognita eggs were extracted from a bulked 20-g subsample of roots from each plot using 1% NaOCl (Hussey and Barker, 1973). Charleston study. The seeds of all of the Received for publication 20 May 2002 . Accepted for publication 15 July 2002. We thank S.B. Merrill, L. J. Still, F. Maguire, R. Reeves, and P. Berland for technical assistance in conducting the experiments. Mention of a trademark, proprietary product, or ven- dor does not constitute a guarantee or warranty of the product by the U.S. Dept. of Agriculture and does not imply its approval to the exclusion of other products or vendors that also may be suitable. 1 Research Plant Pathologist. 2 Research Geneticist. 3 Professor of Plant Pathology. 4 Senior County Extension Agent, Bamberg County, S.C. 5 Senior Associate County Extension Agent, Barnwell County, S.C. nematicides may have varying degrees of use- fulness for controlling root-knot nematodes in vegetable crops, environmental concerns and high costs of reregistration may limit these pesticides as feasible alternatives to methyl bromide. Resistant cultivars may provide the most economical and environmentally benign alternative to pesticides for managing root- knot nematodes. The U.S. Vegetable Laboratory, USDA, Agricultural Research Service (ARS), Charles- ton, S.C., released the root-knot nematode resistant bell pepper cultivars Charleston Belle and Carolina Wonder in 1997 (Fery et. al., 1998). Charleston Belle and Carolina Won- der are the only root-knot nematode resistant bell pepper cultivars available to commercial growers and home gardeners. Both of these open-pollinated cultivars are homozygous for the dominant N gene that controls resistance to M. incognita (Fery et al., 1998), M. arenaria races 1 and 2, and M. javanica (Thies and Fery, 2000). Although the reactions to root-knot nematodes of ‘Charleston Belle , ‘Carolina Wonder , and their respective near-isogenic susceptible parents, ‘Keystone Resistant Gi- ant and ‘Yolo Wonder B , have been charac- terized in controlled greenhouse and growth chamber environments (Thies and Fery, 1998; Thies and Fery, 2000; Thies and Fery, 2002), these types of studies have not been conducted under actual field conditions. The objective of the studies reported here was to use these two HORTSCIENCE 38(7):1394–1396. 2003.