The effect of soil temperature on the expression of resistance in several common bean lines carrying resistance to root-knot nematodes (Meloidogyne spp.) was studied under controlled temperatures in temperature tank and growth chamber conditions. Resistance to M. javanica and M. incognita race 1 in bean lines A315, A328, A445, G1805, and G2618 was stable at 24-30 C. However, there was a significant increase in reproduction of M. javanica on A315, A328, and A445 when temperature was increased from 26 to 30 C. This increase did not reflect a change from a resistant to a susceptible reaction or classification. Resistance in A315 is derived from G1805, whereas resistance in A328 and A445 is derived from G2618. Alabama No. 1, PI 165426, and PI 165435, with resistance to M. incognita race 2, were heat stressed at temperatures above 27 C. Resistance to M. incognita race 2 in Alabama No. 1 and PI 165435 was lost at 30 C, but PI 165426 supported low reproduction of M. incognita race 2 at all temperatures. Poor root development at 30 C may have been responsible, in part, for the poor development of M. incognita race 2 on PI 165426.
common bean; heat stability; Meloidogyne spp.; Phaseolus vulgaris; resistance; root-knot nematode
Two lines of Aegilops squarrosa (G 3489 and G 1279) and Triticum cultivars Anza, Cocorit, Produra, Chinese Spring, Nugaines, and a synthetic hexaploid were screened for resistance to Meloidogyne chitwoodi. Reproduction of M. chitwoodi, expressed as eggs per gram root, was low (P < 0.01) on G 3489 and the synthetic hexaploid. Reproduction on all other cultivars tested was high although differences (P < 0.01) existed among them.
Aegilops squarrosa; Columbia root-knot nematode; Meloidogyne chitwoodi; resistance; Triticum aestivum; wheat
Expression of resistance to Meloidogyne incognita and M. javanica from Aegilops squarrosa was studied in a synthetic allohexaploid produced from Triticum turgidum var. durum cv. Produra and Ae. squarrosa G 3489. The reproductive rate of different races of M. incognita and M. javanica, expressed in eggs per gram of fresh root, was low (P < 0.05) on the synthetic allohexaploid and the resistant parent, Ae. squarrosa G 3489, compared with different bread and durum wheat cultivars. Reproduction of race 2 and race 3 of M. incognita and an isolate of M. javanica was studied on the synthetic allohexaploid and seven cultivars of T. aestivum: Anza, Coker 747, Coker 68-15, Delta Queen, Double Crop, McNair 1813, and Southern Bell. The latter six cultivars are grown in the southeastern United States and reportedly were resistant to M. incognita. Significant differences (P < 0.05) were detected in nematode reproduction on the seven bread wheat cultivars. Reproduction of M. incognita race 3 and M. javanica was highest on Anza. Reproductive rates on the six southeastern United States bread wheat cultivars varied both within and among nematode isolates. The lowest reproductive rates of the three root-knot isolates were detected in the synthetic allohexaploid.
Aegilops squarrosa; Meloidogyne incognita; M. javanica; resistance; root-knot nematode; Triticum aestivum; T. turgidum var. durum; wheat
A granular formulation of a chelate of metham-zinc (CMZ) which liberates the biocidal methyl isothiocyanate was tested for nematicidal activity on Tylenchulus semipenetrans in a jar soil screening and on Meloidogyne javanica (greenhouse test) and M. incognita (field test) infecting tomato. Comparisons were made with 1,3-D in the jar and pot experiments. The CMZ caused only 3.9% mortality of citrus nematode juveniles at 1.0 μg a.i./g soil, but 95.4% mortality at 10.0 μg a.i./g and 100.0% at 100.0 μg a.i./g. CMZ at 10.0 and 100.0 μg a.i./g significantly reduced tomato root infections by M. javanica in the pot test relative to the untreated control. In the field test, CMZ (11.5 g a.i./m² calibration rate) reduced M. incognita populations in the zone of incorporation but not below it, thus failing to provide season-long control for tomato. This material has good nematicidal activity at 10 μg a.i./g or more, but its effectiveness in the field may be limited by its lack of movement.
chemical control; citrus nematode; Lycopersicon esculentum; Meloidogyne incognita; Meloidogyne javanica; methyl isothiocyanate; root-knot nematode; tomato; Tylenchulus semipenetrans; 1,3-dichloropropene
The influence of solutions of ascorbic acid, thiamine, L-arginine, and L-gtutamic acid on egg hatch, juvenile survival, and development and reproduction of Meloidogyne incognita in susceptible and resistant tomatoes was studied. Maximum inhibition of egg hatch occurred at 2,000, 4,000, and 2,000 ppm for ascorbic acid, L-arginine, and L-glutamic acid, respectively. Larval survival was significantly reduced by concentrations of 2,000 ppm ascorbic acid and 1,000 ppm of L-arginine. Maximum inhibition of egg hatch and mortality of juveniles was achieved at a concentration of 4,000 ppm of ascorbic acid and L-arginine. L-glutamic acid and thiamine had respective moderate and minimal toxic effects. Foliar sprays of ascorbic acid, L-arginine, or L-glutamic acid suppressed the numbers of root galls, females, and egg masses on the susceptible tomato cultivar Tropic. Ascorbic acid and L-arginine had highly significant effects when applied to foliage before inoculation with nematodes. Thiamine had little effect. All sprays suppressed the numbers of root galls and females in roots of the resistant cultivar VFN8 when treatments were applied before inoculation. They were not, however, effective as post-inoculation treatments. Growth of a susceptible cultivar was improved by post-inoculation and pre-inoculation treatments when compared with the control plants which had neither nematode infection nor chemical treatment. No positive growth response to chemical treatment was seen in resistant control plants.
amino acid; Meloidogyne incognita; tomato; vitamin
A simulation model of a single sugarbeet, Beta vulgaris L., plant infected by the sugarbeet cyst nematode, Heterodera schachtii Schmidt, was developed using published information. The model is an interactive computer simulation programmed in FORTRAN. Given initial population densities of the nematode at planting, the model simulates nematode population dynamics and the growth of plant tap and fibrous roots. The driving variable for nematode development and plant growth is temperature.
sugarbeet; sugarbeet cyst nematode; simulation modeling; Beta vulgaris; Heterodera schachtii
Lycopersicon glandulosum and L. peruvianum clones and L. esculentum cultivars 'VFN8' (resistant) and 'Rutgers' (susceptible) were tested for their resistance to Meloidogyne incognita (race l) at soil temperatures of 25 and 32 C. L. esculentum cv. VFN8 and L. peruvianum Acc. No. 128657, both of which possess the Mi gene, were resistant at 25 C but were susceptible at 32 C. L. glandulosum Acc. No. 126443 and L. peruvianum Acc. No. 270435, with combined resistance to M. hapla and M. incognita, and L. peruvianum Acc. Nos. 129152 and LA2157, with resistance to M. incognita, were highly resistant at both temperatures. In a second experiment three of these accessions under heat stress simulated by 32 C ambient and soil temperature retained a high level of resistance. Two clones of L. glandulosum Acc. No. 126440, with resistance to M. hapla, were moderately susceptible to M. incognita at 25 and highly susceptible at 32 C. M. incognita produced significantly (P = 0.01) more eggs on L. esculentum cv. Rutgers at 32 than at 25 C. This study supports the existence of genes other than the Mi gene that confer resistance to M. incognita and are functional at high soil temperatures.
root-knot nematodes; resistance; Lycopersicon; soil temperature; tomato
Techniques are described for the extraction and enumeration of cysts and contained eggs from soil samples. The average recovery of cysts from seeded soil samples of differing soil texture was 82.7 ± 2.1%. Recovery from sandy clay soil samples seeded at 1 cyst/100 g soil was 63.4 ± 5.5%; at 4.2 cysts/100 g soil recovery was 89.6 ± 1.8%. Recovery of cysts from naturally infested clay soil was 88.3 ± 2.05%. Egg extraction efficiency for seeded samples was calculated as 78%, and for naturally infested soil was estimated as 83%.
soil sample processing; cyst recovery
Heterodera schaehtii egg number decline under nonhosts was surveyed for 3-4 years at soil depths of 0-30 cm and 30-60 cm in three fields in the Imperial Valley, California. In the two fields continously cropped to alfalfa, annual decline rates were 49 and 63%, respectively, and did not differ (P = 0.05) between depths. In the third field, cropped to annual nonhosts and fallowed, decline rates of 56 and 80% at 0-30-cm and 30-60-cm depths, respectively, were significantly different (P = 0.05). Egg hatch is the major cause of decline. Soil moisture in relation to type of cropping sequence apparently influenced egg hatch and activity of fungal parasites. An interaction matrix is used to assess the importance of biological, environmental, and management factors affecting decline of H. schachtii egg numbers. The required rotation length to non-hosts for various egg densities can be predicted. In coastal California, inclusion of a winter crucifer crop in the rotation increased H. schachtii egg density up to threefold.
sugar-beet cyst nematode; Acremonium strictum; Fusarium oxysporum; crop rotation; population dynamics; biological control
Aqueous solutions of technical-grade phenamiphos [ethyl 3-methyl-4-(methylthio) phenyl (1-methylethyl) phosphoratnidale] were used in hatching chambers to test, under laboratory tory conditions, the effect of phenamiphos on the hatching and movement of Meloiclogyne javanica and Heterodera schachtii. Hatch of M. javanica and H. schachtii eggs was depressed 70 and 88% by nematicide at 0.48 and 4.80 μg/ml, respectively. The infectivity of second-stage larvae of both species was affected by concentrations as low as 0.01 μg/ml. At least 0.5 μg/ml was required to decrease the movement of larvae of M. javanica and H. schachtii. To decrease the movement of H. schachtii males toward females, 10 μg/ml was required. In a field experiment using a 15% granular formulation, 5 kg/ha a.i. significantly reduced infection of sugarbeet roots by H. schachtii.
nematicide; cyst nematode; root-knot nematode; mode of action
In two glasshouse experiments, relations between sugarbeet root dry weight (y, expressed as a percentage of the maximum dry root weight), and preplanting populations of Heterodera schachtii (Pi) were described by the equation y = 100(Z)Pi-T, in which Z = a constant slightly smaller than 1, and T = the tolerance limit (the value of Pi below which damage was not measureable). T varied with temperature; it was 65 eggs/100 g soil at 23 and 27 C and 430 eggs/100 g soil at 19 C. At 15 and 31 C there was no loss of root dry weight up to the maximum preplanting populations tested. In a field experiment in the Imperial Valley the relation between root yield (y) and Pi was y = 100 (0.99886)Pi - 100, and the tolerance limit was 100 eggs/100 g soil.
sugarbeet nematode; Beta vulgaris; pathogenicity
Greenhouse tests were conducted to determine the effects of soil temperature and texture on development of Pratylenchus scribneri and the pathogenicity and reproductive rates of this nematode on selected crop plants. In a sandy loam soil, greatest numbers of P. scribneri were found at 30 and 35 C on sudangrass and sugarbeet, respectively. In a silty clay loam, the nematode reproduced best at 35 C on sugarbeet. Higher populations of P. scribneri were found in the sandy loam than silty clay loam soil at corresponding temperatures. In a pathogenicity test, top and root growth of sudangrass and barley were suppressed by the nematode, whereas no significant growth inhibition was found on wheat and alfalfa. Tests with other vegetable and field crops indicated wide variance in nematode reproduction.
Lesion nematode; pathogenicity; soil temperature; soil type; sudangrass; sugarbeet; barley; wheat; and alfalfa
The pathological effects of Pratylenchus scribneri on susceptible snap bean and resistant lima bean were studied. In a pathogenicity test, the nematode increased nearly 75-fold on snap bean and suppressed top growth. On lima bean, P. scribneri reproduced slowly and did not significantly affect top growth. Discreet lesions formed on lima bean roots, but no lesions developed on snap bean roots. Paraffin sections taken 2, 5, 13, 25, and 32 days after inoculation showed little cellular necrosis in snap bean roots, whereas cells surrounding the nematode in lima bean were extensively necrotic. Cortical cells of infected snap bean roots were almost completely invaded and killed 25 and 32 days after inoculation. The cortex of lima bean tissues was intact, although localized necrotic areas remained at sites of nematode invasion.
host resistance; lesion nematode; Phaseolus lunatus; Phaseolus vulgaris
The adsorption characteristics of two soils for aldicarb sulfoxide were similar to that described by the Freundlich equation, The adsorption constant for the Holtville clay was 3.3, and that of the Buren silt loam, 0.34. Planting beds in a field of Holtville clay and another of Buren silt loam were side-dressed at 25 kg and 50 kg/ha 10% aldicarb (Temik® 10G). Comparison of field measurements of aldicarb concentrations with previous laboratory determinations of aldicarb effects on Heterodera schachtii allowed predictions of soil zones in which hatching, infectivity, and orientation of males to females would be affected. Aldicarb in the soil water of Holtville clay sufficient to interfere with male orientation extended through most of the bed profile to a depth of 46 cm 1 week after the first irrigation. Orientation could be affected in only the top 20 cm of the bed 37 days after treatment and application of 712 mm of irrigation water. In Buren silt loam, disorientation of males was estimated to occur throughout the bed 42 days after treatment and 600 mm irrigation water. Aldicarb persisted in extensive areas of the bed at concentrations sufficient to prevent infection. In small areas of the profile, aldicarb sufficient to inhibit hatching persisted. Amounts of aldicarb in soil water samples obtained directly from beds agreed well with those from the analysis of the air dried soil samples.
nematicide; adsorption isotherm; movement; persistence
The toxic effects of sublethal concentrations ofaldicarb were studied on eggs and second-stage larvae and males of Heterodera schachtii and second-stage larvae only of Meloidogyne javanica in a quartz sand substrate. Aldicarb was more toxic to eggs of H. schachtii than to those of M. javanica. Complete suppression of hatching occurred between 0.48 and 4.8 μg/ml aldicarb for H. schachtii whereas 100% inhibition of hatch of M. javanica occurred between 4.8 and 48.0 μg/ml. M. javanica hatch was stimulated at 0.48 μg/ml aldicarb. Migration of second-stage larvae of H. schachtii and M. javanica in sand columns was inhibited under continuous exposure to 1 μg/ml aldicarb. Infection of sugarbeet and tomato seedlings by larvae was inhibited at 1 μg/ml. H. schachtii males failed to migrate toward nubile females at 0.01 μg/ml aldicarb. This was partially confirmed in a field study in which adding aldicarb to soil resulted in fewer females being fertilized.
cyst nematode; root-knot nematode; nematicide; hatching; movement; sex attractant; infectivity; systemic action; mode of action
Temperature-induced phase transitions estimated by electron spin resonance (ESR) technique were ohscrved in the lipids of several nematode species. In both Meloidogyne javanica and Caenorhahditis elegans, there was a phase transition in their phospholipids from a liquid-crystalline state to a solid gel state at about 10 C. Aphelenchus avenae also had a phase transition, but at about 20 C. With this species, the spin-label motion parameters indicated the transition was from the liquid-crystalline state below 20 C to a more liquid or disordered state above 20 C. Anguina tritici and Meloidogyne hapla, in contrast, had no phase transitions over the entire temperature range studied. Each phase transition detected by ESR was reflected in the respiratory rates of the nematodes, and the temperature of the transition coincides with the environmental adaptation of these species.
The lesion nematode, Pratylenchus thornei, was clearly demonstrated as a parasite of wheat. It reduced plant stands and stunted plants in the field under the environmental conditions found in Sonora, Mexico. Other soil organisms also may have contributed to the problem. The nematode is widely distributed throughout the wheat-growing region, and may be a problem each growing season. Nematicides controlled the nematode and increased yields, but they were not economical. No resistance was found in existing commercial wheat cultivars. A pest management approach using variety selection, nitrogen fertilizer, planting in cool soil (15 C) and a crop rotation avoiding wheat after wheat was the most practical solution to this problem on a commercial scale.
lesion nematode; resistance; crop rotation; chemical control; fertilizer; temperature; nematicides