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Alexis K. Nagel, Guido Schnabel, Cesar Petri and Ralph Scorza

inoculated seedlings and were plated on PARPH [PARP + 50 mg 5-methylisoxazol-3-ol (hymexazol)] selective medium to confirm the presence of the P. cinnamomi . Experimental plum plants were challenged with Meloidogyne incognita (Kofoid & White) Chitwood to

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Jerry T. Walker

Twenty herb species were exposed to root-knot nematode under greenhouse conditions. The root systems were examined for root gall development and nematode reproduction as an indication of host suitability. The herbs evaluated were balm (Melissa officinalis L.), basil (Ocimum basilicum L.), catnip (Nepeta cataria L.), chamomile (Matricaria recutita L.), coriander (Coriandrum sativium L.), dill (Anethum graveolens L.), fennel (Foeniculum vulgare Mill.), hyssop (Hyssopus officinalis L.), lavender (Lavandula augustifolia Mill.), oregano (Origanum vulgare L.), peppermint (Mentha ×piperita L.), rocket-salad (Erurca vesicaria L.), rosemary (Rosmarinus officinalis L.), rue (Ruta graveolens L.), sage (Salvia officinalis L.), savory (Satureja hortensis L.), sweet marjoram (Origanum majorana L.), tansy (Tanacetum vulgare L.), thyme (Thymus vulgaris L.), and wormwood (Artemisia absinthium L.). Peppermint, oregano, and marjoram consistently were free of root galls after exposure to initial nematode populations of two or 15 eggs/cm3 of soil medium and were considered resistant. All other herb species developed root galls with accompanying egg masses, classifying them as susceptible or hypersusceptible to root-knot nematode. The highest initial nematode egg density (15 eggs/cm3) significantly decreased dry weights of 14 species. The dry weights of other species were unaffected at these infestation densities after 32- to 42-day exposure.

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Judy A. Thies, Jennifer J. Ariss, Richard L. Hassell, Sharon Buckner and Amnon Levi

The southern RKN ( Meloidogyne incognita ) is a serious constraint to U.S. watermelon production and can significantly reduce watermelon yields in the southern United States ( Davis, 2007 ; Sumner and Johnson, 1973 ; Thies, 1996 ). Pre

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Andreas Westphal, Nicole L. Snyder, Lijuan Xing and James J. Camberato

by Fusarium oxysporum f. sp. niveum , mature watermelon vine decline (MWVD) caused by unknown agents, Monosporascus vine decline caused by Monosporascus cannonballus , root-knot nematodes, Meloidogyne incognita , and, in some areas, M. javanica

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J.C. Cervantes-Flores, G.C. Yencho and E.L. Davis

Sweetpotato [Ipomoea batatas (L.) Lam.] genotypes were evaluated for resistance to North Carolina root-knot nematode populations: Meloidogyne arenaria (Neal) Chitwood races 1 and 2; M. incognita (Kofoid & White) Chitwood races 1, 2, 3, and 4; and M. javanica (Treub) Chitwood. Resistance screening was conducted using 150-cm3 Conetainers containing 3 sand: 1 soil mix. Nematode infection and reproduction were assessed as the number of egg masses produced by root-knot nematodes per root system. Host suitability for the root-knot nematode populations differed among the 27 sweetpotato genotypes studied. Five genotypes (`Beauregard', L86-33, PDM P6, `Porto Rico', and `Pelican Processor') were selected for further study based on their differential reaction to the different root-knot nematodes tested. Two African landraces (`Tanzania' and `Wagabolige') were also selected because they were resistant to all the nematode species tested. The host status was tested against the four original M. incognita races, and an additional eight populations belonging to four host races, but collected from different geographical regions. The virulence of root-knot nematode populations of the same host race varied among and within sweetpotato genotypes. `Beauregard', L86-33, and PDM P6 were hosts for all 12 M. incognita populations, but differences in the aggressiveness of the isolates were observed. `Porto Rico' and `Pelican Processor' had different reactions to the M. incognita populations, regardless of the host race. Several clones showed resistance to all M. incognita populations tested. These responses suggest that different genes could be involved in the resistance of sweetpotato to root-knot nematodes. The results also suggest that testing Meloidogyne populations against several different sweetpotato hosts may be useful in determining the pathotypes affecting sweetpotato.

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Susan L.F. Meyer, Inga A. Zasada, Shannon M. Rupprecht, Mark J. VanGessel, Cerruti R.R. Hooks, Matthew J. Morra and Kathryne L. Everts

. London, UK Lazzeri, L. Curto, G. Dallavalle, E. D’Avino, L. Malaguti, L. Santi, R. Patalano, G. 2009 Nematicidal efficacy of biofumigation by defatted Brassicaceae meal for control of Meloidogyne incognita (Kofoid et White) Chitw. on a full field

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Zhen-Xiang Lu, Gregory L. Reighard, Andrew P. Nyczepir, Thomas G. Beckman and David W. Ramming

Two F1 hybrid Prunus rootstocks, K62-68 and P101-41, developed from a cross of `Lovell' [susceptible to both Meloidogyne incognita (Kofoid and White) Chitwood and M. javanica (Treub) Chitwood] and `Nemared' (resistant to both root-knot nematode species), were selfed to produce two F2 seedling populations. Vegetative propagation by herbaceous stem cuttings was used to produce four or eight self-rooted plants of each F2 seedling for treatment replications. Eggs of M. incognita and M. javanica were inoculated into the potted media where plants were transplanted, and plants were harvested and roots examined for signs and symptoms associated with root-knot nematode infection ≈120 days later. Segregation ratios in both F2 families suggested that resistance to M. incognita in `Nemared' is controlled by two dominant genes (Mi and Mij) and that to M. javanica by a single dominant gene (Mij). Thus, Mij conveys resistance to both M. incognita and M. javanica.

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Judy A. Thies, Amnon Levi, Jennifer J. Ariss and Richard L. Hassell

southern RKN ( Meloidogyne incognita ), peanut RKN ( Meloidogyne arenaria ), and Javanese RKN ( Meloidogyne javanica ). The watermelon plants grafted on ‘RKVL-318’ rootstock had considerable yield advantage over non-grafted watermelon plants in fields

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Richard L. Fery and Judy A. Thies

homozygous for a dominant gene conditioning a high level of resistance to the southern root-knot nematode [ Meloidogyne incognita (Chitwood) Kofoid and White]. The southern root-knot nematode is a major pest of peppers in the United States, and all Habanero

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Anne M. Gillen and Fredrick A. Bliss

Peach rootstock breeding may be accelerated by utilization of molecular markers linked to the root-knot nematode resistance locus (Mi) to screen segregating populations. A genetic linkage map was constructed using RFLP markers in an F2 population (PMP2) that is segregating for this locus. PMP2 is derived from a controlled cross of the relatively diverse peach rootstocks Harrow Blood (susceptible) and Okinawa (homozygous resistant). Bulked Segregant Analysis was applied using RAPD markers. A single small (227 base pairs) RAPD marker was found to be linked to the dominant resistant allele of Mi at a distance of 10 cM. This new marker joined the Mi locus to the RFLP linkage map and showed that two dominant RFLP markers are located between the RAPD marker and Mi. RFLPS are expensive, time-consuming and RAPD markers are unreliable, and therefore both are unsuitable for screening breeding populations. We attempted to convert the RAPD marker to a more breeder-friendly CAPS marker. The converted CAP marker was dominant. Attempts to convert the CAP marker to a co-dominant marker were not successful. The utility of the CAP marker was tested in an open pollinated F2 population derived from the F1 parent of PMP2 and in several rootstocks. The genetic linkage map was compared to other Prunus maps. The PMP2 linkage group containing the Mi locus can be related to the peach × almond linkage group which contains the phosphoglucomutase Pgm-1 locus.