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Four Capsicum chinense cultigens with known reactions to Meloidogyne incognita were characterized for resistance to M. arenaria races 1 and 2, M. hapla, and M. javanica, in greenhouse and growth-chamber tests. The M. incognita-resistant cultigens PA-353, PA-398, and PA-426 exhibited high resistance to M. arenaria race 1; the M. incognita-susceptible PA-350 was susceptible to M. arenaria race 1. M. arenaria race 2 and M. javanica were not highly pathogenic to any of the C. chinense cultigens. PA-353, PA-398, and PA-426, however, supported an average of 98.1 and 94.8% fewer (P < 0.05) M. arenaria race 2 and M. javanica eggs per gram fresh root, respectively, than PA-350. M. hapla was pathogenic to all four C. chinense cultigens. PA-353, PA-398, and PA-426 will be useful sources of resistance to M. arenaria races 1 and 2, M. javanica, and M. incognita, for developing resistant habanero pepper cultivars; however, an alternative source of resistance must be identified for M. hapla.

‘Charleston Belle’, a root-knot nematode-resistant pepper (Capsicum annuum var. annuum [Grossum Group]), and its susceptible recurrent parent, ‘Keystone Resistant Giant’, were compared as spring crops for managing the southern root-knot nematode (Meloidogyne incognita) in fall-cropped cucumber (Cucumis sativus) and squash (Cucurbita pepo) at Blackville, SC and Tifton, GA. ‘Charleston Belle’ exhibited minimal root galling and nematode reproduction, and ‘Keystone Resistant Giant’ exhibited severe root galling and high nematode reproduction. Cucumber grown in plots following ‘Charleston Belle’ had lower (P ≤ 0.001) root gall severity indices than following ‘Keystone Resistant Giant’ (4.2 versus 4.9, respectively). Cucumber yields were 87% heavier (P ≤ 0.0001) and numbers of fruit were 85% higher (P ≤ 0.0001) in plots previously planted to ‘Charleston Belle’ than to ‘Keystone Resistant Giant’. Squash grown in plots following ‘Charleston Belle’ had lower (P ≤ 0.001) root gall severity indices than following ‘Keystone Resistant Giant’ (4.0 versus 4.8, respectively). Squash yields were 55% heavier (P ≤ 0.01) and numbers of fruit were 50% higher (P ≤ 0.001) in plots previously planted to ‘Charleston Belle’ than to ‘Keystone Resistant Giant’. These results demonstrate that root-knot nematode-resistant bell pepper cultivars such as ‘Charleston Belle’ are useful tools for managing M. incognita in double-cropping systems with cucurbit crops.

Genetic resistance to Meloidogyne incognita in pepper (Capsicum annuum) has been well characterised for the N and Me3 resistance genes. However, there are no studies comparing the effects of these two genes directly or investigating the combined effects when both genes are present together. Several studies were undertaken to investigate the relationship of the N and Me3 gene systems to one another and to assess whether these two genes are allelic or truly separate genes. Two genotypes homozygous for the N gene (‘Carolina Wonder’ and ‘Charleston Belle’) and two genotypes homozygous for the Me3 gene (HDA 149 and PM 687) were compared in a replicated greenhouse test for reaction to M. incognita race 3. There were no significant differences between the resistant reactions of genotypes possessing the N or Me3 gene. Allelism tests were performed using the F2 populations of the parental genotypes HDA 149 × ‘Charleston Belle’ and HDA 149 × ‘Carolina Wonder’. The results of these studies clearly show the N and Me3 genes to be distinct, separate dominant resistance genes conferring resistance to M. incognita race 3 and not alleles of the same gene.

Root-knot nematodes (Meloidogyne spp.) cause extensive damage to watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai var. lanatus], and resistance to root-knot nematodes has not been identified in any watermelon cultivar. Twenty-six U.S. Plant Introductions (PIs) of Citrullus lanatus (Thunb.) Matsum. & Nakai var. citroides (L. H. Bailey) Mansf., one PI of C. lanatus var. lanatus, and three PIs of Citrullus colocynthis (L.) Schrad. were evaluated in greenhouse tests for resistances to Meloidogyne incognita (Kofoid & White) Chitwood race 3 and Meloidogyne arenaria (Neal) Chitwood race 2. Twenty-three of the C. lanatus var. citroides PIs and the C. lanatus var. lanatus PIs were previously identified as moderately resistant to M. arenaria race 1. Overall, the C. lanatus var. citroides PIs exhibited low to moderate resistance, and the C. lanatus var. lanatus and C. colocynthis PIs were susceptible to both M. incognita race 3 and M. arenaria race 2. The C. lanatus var. citroides PI 482303 was the most resistant PI with gall index (GI) = 2.88 and reproductive index (RI) = 0.34 for M. incognita race 3 and GI = 3.46 and RI = 0.38 for M. arenaria race 2 (1 = no galling; 5 = 26% to 38% root system galled; 9 = 81% to 100% root system galled). These results demonstrate that there is significant genetic variability within C. lanatus var. citroides for reaction to M. incognita and M. arenaria race 2, and several C. lanatus var. citroides PIs may provide sources of resistance to root-knot nematodes.

The market for organically grown fruits and vegetables has been increasing in recent years, and research is vital for obtaining optimal quality and yields in organic production systems. Scientists at the United States Department of Agriculture-Agricultural Research Service (USDA-ARS) are investigating methods for managing plant-parasitic nematodes on these crops, and studies that involve practices appropriate for organic vegetable production are reviewed in this paper. The projects summarized here focus primarily on suppression of root knot nematode species, including Meloidogyne arenaria (Neal) Chitwood, M. hapla Chitwood, M. incognita (Kofoid and White) Chitwood and M. javanica (Treub) Chitwood. Projects from Florida include investigations of plant growth-promoting rhizobacteria (PGPR) and chitin amendments for management of nematodes on pepper (Capsicum annuum L.), muskmelon (Cucumis melo L.), and tomato (Solanum lycopersicum L.). In South Carolina, research programs focus on the identificatio...

Several species of root-knot nematodes [Meloidogyne incognita (Kofoid & White) Chitwood, M. arenaria (Neal) Chitwood, M. javanica (Treub) Chitwood, and M. hapla Chitwood] are major pests of peppers (Capsicum spp.) in the United States and worldwide. Resistance to M. incognita, M. arenaria, and M. javanica has been identified in several Capsicum accessions, but there are few reports of resistance to M. hapla. Therefore, we selected a 10% core (440 accessions) of the 14 available Capsicum spp. in the Capsicum germplasm collection (3,731 accessions) maintained by the U.S. Dept. of Agriculture (USDA), and evaluated this core for resistance to M. hapla in unreplicated greenhouse tests. The 11 best (most resistant) and the 3 worst (most susceptible) accessions identified in these unreplicated tests were re-evaluated in a replicated greenhouse test. Seven of these 11 “best” accessions (PI 357613, PI 357503, PI 439381, PI 297493, PI 430490, PI 267729, and PI 441676) exhibited root gall severity indices M. hapla eggs were extracted per gram of fresh root tissue and the reproductive index was >1.0 for each of these accessions. These observations suggest that the most resistant accessions tested are somewhat susceptible to M. hapla. The results of our evaluation of a core of the USDA Capsicum germplasm collection demonstrates clearly that there is significant genetic variability within the overall collection for M. hapla resistance. Additionally, these results identify portions of the collection where future evaluations for M. hapla resistance should be focused. For example, the origin of the two most promising C. annuum accessions (PI 357613 and PI 357503) in the core was Yugoslavia. Thus, additional accessions from this temperate region of the world should receive priority attention in any effort to identify better sources of resistance in C. annuum to M. hapla.

Expression of the N gene, which confers resistance to southern root-knot nematode (Meloidogyne incognita Kofoid and White) in bell pepper ((Capsicum annuum L. var. annuum (Grossum Group)), is modified at high temperatures (28 °C and 32 °C), but its expression in the heterozygous condition (Nn) has not been documented at moderate or high temperatures. Responses of the near-isogenic bell pepper cultivars, Charleston Belle and Keystone Resistant Giant (differing at the N locus), and the F1 and reciprocal F1 crosses between these cultivars to M. incognita race 3 were determined at 24, 28, and 32 °C in growth chamber experiments. 'Keystone Resistant Giant' (nn) was susceptible at 24, 28, and 32 °C. 'Charleston Belle' (NN) exhibited high resistance at 24 °C and resistance was partially lost at 28 and 32 °C. However, at 32 °C root gall and egg mass severity indices for 'Charleston Belle' were still in the resistant range, and the number of M. incognita eggs per gram fresh root and reproductive index were 97% and 90% less, respectively, than for 'Keystone Resistant Giant'. Responses of the F1 and F1 reciprocal hybrid populations to M. incognita were similar to the response of the resistant parent at all temperatures. Root fresh weights and top dry weights indicated that both hybrid populations tolerated M. incognita infections at least as well as 'Charleston Belle'. These findings indicate that i) only one of the parental inbred lines needs to be converted to the NN genotype to produce F1 hybrid cultivars with fully functional N-type resistance to M. incognita; and ii) cytoplasmic factors are not involved in expression of N-type resistance and the resistant parental inbred can used to equal advantage as either the paternal or the maternal parent. F1 hybrid (Nn) bell pepper cultivars. The utility of F1 hybrids heterozygous for the N gene will depend on expression of resis- tance to M. incognita, especially at high temperatures. However, expression of the N gene in the heterozygous (Nn) condition has not been evaluated at any temperature. Therefore, the objectives of this study were to 1) determine expression of resistance to M. incognita conferred by the homozygous (NN) and heterozygous (Nn) conditions of the N locus at moderate and high temperatures, and 2) determine whether there are any cytoplasmic effects on expression of the N gene in F1 bell pepper hybrids.

Two isogenic sets of bell pepper (Capsicum annuum L.) lines (differing at the N root-knot nematode resistance locus) were characterized for resistance to Meloidogyne arenaria (Neal) Chitwood races 1 and 2, M. hapla Chitwood, and M. javanica (Treub) Chitwood in greenhouse and growth chamber tests. The isogenic sets of C. annuum were 'Charleston Belle' (NN) and 'Keystone Resistant Giant' ( nn-recurrent parent), and 'Carolina Wonder' ( NN) and 'Yolo Wonder B' ( nn- recurrent parent). Meloidogyne arenaria race 1 is pathogenic to C. annuum. 'Charleston Belle' and 'Carolina Wonder' exhibited high resistance to M. arenaria race 1. Their respective recurrent backcross parents, 'Keystone Resistant Giant' and 'Yolo Wonder B', were susceptible to M. arenaria. Meloidogyne arenaria race 2 and M. javanica are not highly pathogenic to pepper. However, 'Charleston Belle' and 'Carolina Wonder' both exhibited higher ( P ≤ 0.05) resistance to M. arenaria race 2 and M. javanica than 'Keystone Resistant Giant' and 'Yolo Wonder B'. Meloidogyne hapla is pathogenic to pepper. Both 'Charleston Belle' and 'Carolina Wonder' and their respective recurrent parents, 'Keystone Resistant Giant' and 'Yolo Wonder B', were susceptible to M. hapla. We concluded that the N gene confers resistance to M. arenaria races 1 and 2, and M. javanica in C. annuum, but the N gene does not condition resistance to M. hapla. 'Santanka xS' and '405B Mexico' was conditioned by a single dominant gene which was designated the N gene. Hare (1966) backcrossed the N gene into pimiento pepper, and subsequently released the M. incognita-resistant pimiento pepper cultivar, 'Mississippi Nemaheart'. Resistance to M. incognita in 'Carolina Cayenne' is also conferred by the N gene and an additional recessive gene (Fery and Dukes, 1996). Recently, 'Charleston Belle' and 'Carolina Wonder', the first bell pepper cultivars with resistance to M. incognita, were developed and released by scientists at the U.S. Vegetable Laboratory, U.S. Department of Agriculture (USDA), Agricultural Research Service (ARS), Charleston, S.C. (Fery et al., 1998). Both of these open-pollinated cultivars are homozygous for the N gene. These cultivars provide a feasible alternative to preplant fumigation of soil with methyl bromide for managing the southern root-knot nematode, M. incog- nita, in bell pepper plantings. However, the reaction of these resistant cultivars to the other major species of root-knot nematodes will be important in making cultivar recommendations and in designing cropping systems to manage the four major species of root-knot nematodes. The purpose of these studies was to deter- mine whether the N gene confers resistance to M. arenaria races 1 and 2, M. hapla, and M. javanica in two sets of isogenic lines of C. annuum that differ in the presence or absence of the N gene.

Scotch Bonnet and Habanero peppers, extremely pungent cultivar classes of Capsicum chinense Jacq., are increasing in popularity in the United States. Because the southern root-knot nematode, Meloidogyne incognita (Kofoid & White) Chitwood, is a major pest of many C. annuum cultivars, a series of greenhouse and field experiments was conducted to determine if Scotch Bonnet and Habanero peppers from available commercial and private sources also are vulnerable to the pest. In an initial greenhouse test, a collection of 59 C. chinense cultigens was evaluated for reaction to M. incognita race 3. All cultigens obtained from commercial sources were moderately susceptible or susceptible. However, four accessions obtained through Seed Savers Exchange listings exhibited high levels of resistance. Three of these cultigens (PA-353, PA-398, and PA-426) were studied in subsequent greenhouse and field plantings, and each was confirmed to have a level of resistance similar to that available in C. annuum. All three of the resistant cultigens are well-adapted and each is potentially useful in commercial production without further development. None of the Habanero cultigens was resistant to the southern root-knot nematode. The resistant Scotch Bonnet cultigens may serve as sources of resistance for development of root-knot nematode—resistant Habanero peppers.

Root-knot nematode-resistant `Charleston Belle' bell pepper (Capsicum annuum L. var. annuum) and metam sodium treatment were evaluated for managing the southern root-knot nematode [Meloidogyne incognita (Chitwood) Kofoid and White] in fall-cropped cucumber (Cucumis sativus L.). `Charleston Belle' and its susceptible recurrent parent, `Keystone Resistant Giant', were planted as spring crops at Blackville, S.C., and Tifton, Ga. `Charleston Belle' exhibited high resistance and `Keystone Resistant Giant' was susceptible at both locations. After termination of the bell pepper crop, one-half of the plots were treated with metam sodium delivered through the drip irrigation system. Cucumber yields and numbers of fruit were highest for cucumber grown in plots treated with metam sodium following either `Charleston Belle' or `Keystone Resistant Giant'; however, root gall severity and numbers of M. incognita eggs in the roots were lowest for cucumber grown in plots treated with metam sodium following `Charleston Belle'. Conversely, root gall severity and nematode reproduction were highest for cucumber grown in plots following `Keystone Resistant Giant' without metam sodium treatment. Application of metam sodium through the drip irrigation system following a spring crop of root-knot nematode-resistant bell pepper should reduce severity of root galling and reproduction of M. incognita as well as increase fruit yield of fall-cropped cucumber.

Resistance of two sets of bell pepper [(Capsicum annuum L. var. annuum (Grossum 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 susceptible 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 peppers should provide economical and environmentally compatible alternatives to methyl bromide and other nematicides for managing M. incognita.

A 3-year field study was conducted at Blackville, S.C., to evaluate the potential of using resistant pepper (Capsicum annuum L.) cultivars as a rotation crop for managing the southern root-knot nematode [Meloidogyne incognita (Kofoid and White) Chitwood]. The experiment was a split-plot with main plots arranged in a randomized complete-block design. In 1993, the entire experimental site was infested with M. incognita by inoculating a planting of susceptible PA-136 cayenne pepper with eggs of M. incognita race 3. In 1994, the main plots were planted to either highly resistant `Carolina Cayenne' or its susceptible sibling line PA-136. In 1995, `Carolina Cayenne' and the susceptible bell cultivars California Wonder and Keystone Resistant Giant were grown as subplots in each of the original main plots. `Carolina Cayenne' plants were unaffected by the previous crop. Previous cropping history, however, had a significant impact on the performance of the bell cultivars; the mean galling response was less (P < 0.01) and the yield was 2.8 times greater (P < 0.01) in the main plots previously cropped with `Carolina Cayenne' than in those previously cropped with PA-136. These results suggest that resistant pepper cultivars have considerable merit as a rotation crop for managing M. incognita infestations in soils used for growing high-value vegetables.

A series of greenhouse and field studies was conducted over 9 years to characterize three new sources of resistance in cowpea [Vigna unguiculata (L.) Walp.] to the southern root-knot nematode [Meloidogyne incognita (Kofoid & White) Chitwood] and to determine if the resistances are conditioned by genes allelic to the Rk root-knot nematode resistance gene in `Mississippi Silver'. Three plant introductions (PI), PI 441917, PI 441920, and PI 468104, were evaluated for reaction to M. incognita in four greenhouse tests, and in every test each PI exhibited less galling, egg mass formation, or egg production than `Mississippi Silver'. F2 populations of the crosses between `Mississippi Silver' and each of the three resistant PIs were also evaluated for root-knot nematode resistance in a greenhouse test. None of the F2 populations segregated for resistance, indicating that PI 441917, PI 441920, and PI 468104 each has a gene conditioning resistance that is allelic to the Rk gene in `Mississippi Silver'. Our observations on the superior levels of resistances exhibited by PI 441917, PI 441920, and PI 468104 suggest that the allele at the Rk locus in these lines may not be the Rk allele, but one or more alleles that condition a superior, dominant-type resistance. The availability of additional dominant alleles would broaden the genetic base for root-knot nematode resistance in cowpea.