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1.  Virulence of Meloidogyne incognita to expression of N gene in pepper 
Journal of Nematology  2011;43(2):90-94.
Four pepper genotypes classified as resistant and four pepper genotypes classified as susceptible to several avirulent populations of M. incognita were compared for their reactions against a population of Meloidogyne incognita (Chitwood) Kofoid and White which had been shown to be virulent to resistant bell pepper (Capsicum annuum) in preliminary tests. The virulent population of M. incognita originated from a commercial bell pepper field in California. The resistant pepper genotypes used in all experiments were the Capsicum annuum cultivars Charleston Belle, Carolina Wonder, and Carolina Cayenne, and the C. chinense cultigen PA-426. The susceptible pepper genotypes used in the experiments were the C. annuum cultivars Keystone Resistant Giant, Yolo Wonder B, California Wonder, and the C. chinense cultigen PA-350. Root gall indices (GI) were ≥ 3.0 for all genotypes in both tests except for PA-426 (GI=2.57) in test 1 and ‘Carolina Cayenne’ (GI=2.83) in test 2. Numbers of eggs per gram fresh root weight ranged from 20,635 to 141,319 and reproductive indices ranged from 1.20 to 27.2 for the pepper genotypes in both tests, indicating that all eight pepper genotypes tested were susceptible to the M. incognita population used in these tests. The M. incognita population used in these studies overcame resistance conferred by the N gene in all resistant genotypes of both C. annuum and C. chinense.
PMCID: PMC3380459  PMID: 22791917
Capsicum annuum var. annuum; Capsicum chinense; Meloidogyne incognita; methyl bromide alternatives; nematode resistance
2.  Red Food Coloring Stain: New, Safer Procedures for Staining Nematodes in Roots and Egg Masses on Root Surfaces 
Journal of Nematology  2002;34(2):179-181.
Acid fuchsin and phloxine B are commonly used to stain plant-parasitic nematodes in roots and egg masses on root surfaces, respectively. Both stains can be harmful to both the user and the environment and require costly waste disposal procedures. We developed safer methods to replace both stains using McCormick Schilling red food color. Eggs, juveniles, and adults of Meloidogyne incognita stained in roots with red food color were equally as visible as those stained with acid fuchsin. Egg masses stained with red food color appeared as bright-red spheres on the root surfaces and were highly visible even without magnification. Replacement of acid fuchsin and phloxine B with red food color for staining nematodes is safer for the user and the environment, and eliminates costly waste disposal of used stain solutions.
PMCID: PMC2620550  PMID: 19265929
environmental safety; Meloidogyne spp.; resistance; root-knot nematode; staining procedures; worker protection
3.  Heat Stability of Resistance to Meloidogyne incognita in Scotch Bonnet Peppers ( Capsicum chinense Jacq.) 
Journal of Nematology  2000;32(4):356-361.
Stability of resistance to Meloidogyne incognita (Kofoid &White) Chitwood was determined in pepper (Capsicum chinense Jacq. and C. annuum L.) at 24, 28, and 32 °C. Reactions of the C. annuum cultivars Charleston Belle and Keystone Resistant Giant and the C. chinense cultigens PA-426 and PA-350 to M. incognita were compared. Charleston Belle is homozygous for the N gene that confers resistance to M. incognita in C. annuum, and Keystone Resistant Giant is the susceptible recurrent parent of Charleston Belle. PA-426 is homozygous for a single dominant resistance gene that is allelic to the N gene, and PA-350 is susceptible. Root galling, egg-mass production, numbers of eggs per g fresh root, and reproductive factor of M. incognita increased for all pepper genotypes as temperature increased. Severity of root galling and nematode reproduction were less for PA-426 and Charleston Belle compared to PA-350 and Keystone Resistant Giant at all temperatures. However, both PA-426 and Charleston Belle exhibited a partial loss of resistance at the higher temperatures. For example, at 32 °C, the numbers of M. incognita eggs per g fresh root and the reproductive index for PA-426 and Charleston Belle were in the susceptible range. Nevertheless, the gall index for both cultivars was still within the resistant range. Both PA-350 and Keystone Resistant Giant exhibited highly susceptible reactions at 28 and 32 °C. Although the resistances of PA-426 and Charleston Belle were somewhat compromised at high temperatures, cultivars possessing these resistances will still be useful for managing M. incognita under high soil temperatures.
PMCID: PMC2620467  PMID: 19270989
Capsicum annuum L.; C. chinense Jacq.; habanero; heat stability; Meloidogyne incognita; resistance; root-knot nematode; Scotch Bonnet pepper; soilborne pathogen; soil temperature; vegetable breeding
4.  Inheritance of Resistance to Pratylenchus penetrans in Alfalfa 
Journal of Nematology  1994;26(4):452-459.
Fifty-two alfalfa (Medicago sativa L.) clones, randomly selected from the cultivar Baker and the experimental line MNGRN-4, were evaluated for resistance (based on nematode reproduction) to Pratylenchus penetrans in growth chamber tests (25 C). Twenty-five clones, representing the range of nematodes and eggs per plant, were selected and retested. Four moderately resistant and two susceptible alfalfa clones were identified. Inheritance of resistance to P. penetrans was studied in these six clones using a diallel mating design. The S₁, Fl, and reciprocal progenies differed for numbers of nematodes and eggs per g dry root and for shoot and root weights (P < 0.05). Resistance, measured as numbers of nematodes in roots, was correlated between parental clones and their S₁ families (r = 0.94), parental clones and their half-sib families (r = 0.81), and S₁ and half-sib families (r = 0.88). General combining ability (GCA) effects were significant for nematode resistance traits. Both GCA and specific combining ability (SCA) effects were significant for plant size traits, but SCA was more important than GCA in predicting progeny plant size. Reciprocal effects were significant for both nematode resistance and plant size traits, which may slow selection progress in long-term selection programs. However, the GCA effects are large enough that breeding procedures that capitalize on additive effects should be effective in developing alfalfa cultivars with resistance to P. penetrans.
PMCID: PMC2619523  PMID: 19279915
alfalfa; inheritance of resistance; Medicago sativa; Pratylenchus penetrans; nematode; nematode resistance; root-lesion nematode

Results 1-4 (4)