Development of Heterodera glycines on Soybean Damaged by Soybean Looper and Stem Canker

Short-term greenhouse studies with soybean (Glycine max cv. Bragg) were used to examine interactions between the soybean cyst nematode (Heterodera glycines) and two other common pests of soybean, the stem canker fungus (Diaporthe phaseolorum var. caulivora) and the soybean looper (Pseudoplusia includens), a lepidopterous defoliator. Numbers of cyst nematode juveniles in roots and numbers of cysts in soil and roots were reduced on plants with stem cankers. Defoliation by soybean looper larvae had the opposite effect; defoliation levels of 22 and 64% caused stepwise increases in numbers of juveniles and cysts in both roots and soil, whereas numbers of females in roots decreased. In two experiments, stem canker length was reduced 40 and 45% when root systems were colonized by the soybean cyst nematode. The absence of significant interactions among these pests indicates that the effects of soybean cyst nematode, stem canker, and soybean looper on plant growth and each other primarily were additive.     

Influence of fall armyworm previous experience with soybean genotypes on larval feeding behavior

Previous experience on host plants can modify insect feeding behavior. Because insect habituation and induction of preference to host plants are variable across species of plants and insects, it is necessary to investigate each insect-plant interaction to determine whether this phenomenon occurs or not in the system. In this study we investigated the potential occurrence of habituation and induction of preference in fall armyworm (FAW) Spodoptera frugiperda to soybean genotypes. Neonate FAW larvae reared on artificial diet were divided into four treatment groups and fed for one generation with either the resistant soybeans PI 227687 or IAC 100 or the susceptible soybeans BRS Valiosa RR or IGRA RA 626 RR. Biological parameters of FAW were recorded. Eggs obtained from FAW of each genotype group were separated, and the newly hatched larvae were fed on the same genotypes experienced by their parents for additional 8 days. FAW larval preference and leaf area consumed were evaluated in choice feeding assays with the four soybean genotypes within a 24-h period. Genotypes PI 227687 and IAC 100 negatively affected FAW development, demonstrating they are FAW-resistant. FAW larvae exposed to both resistant genotypes consumed more foliage of genotype IGRA RA 626 RR in the choice assays, whereas larvae reared on both susceptible genotypes did not show any preference. From our preliminary study, FAW does not show habituation and induction of preference toward the experienced soybean genotypes. The importance of our findings to host plant resistance and insect-plant biology fields is discussed.     

Foliage consumption and larval development of parasitized and unparasitized soybean looper,Pseudoplusia includens [Lep.: Noctuidae], reared on a resistant soybean genotype and effects on an associated parasitoid,Compidosoma truncatellum [Hym.: Encyrtidae]

Field grown foliage from the resistant soybean [Glycine max (L.) Merrill] breeding line GAT “81–327” and the susceptible cultivar “Ransom” was used to rear unparasitized larvae of the soybean looper (SBL),Pseudoplusia includens (Walker), and larvae parasitized byCopidosoma truncatellum (Dalman). SBL larvae, whether parasitized or not, consumed more foliage when fed “Ransom”. Unparasitized larvae reared on “81–327” had longer developmental times and suffered greater mortality than unparasitized larvae reared on “Ransom”. Parasitization of SBL larvae byC. truncatellum increased total foliage consumption of both soybean lines. Parasitized larvae reared on the resistant “81–327” weighed less and yielded fewer parasitoid adults.

---

Résumé Des larves dePseudoplusia includens (Walker) parasitées ou non parCopidosoma truncatellum (Dalman) ont été nourries des feuilles de deux lignées de soja [Glycine max (L.) Merrill] l'une, GAT “81–327” résistante et l'autre, “Ransom” sensible. Les larves deP. includens qu'elles soient parasitées ou non consommaient plus de feuillage lorsqu'elles étaient nourries de la lignée “Ransom”. Les larves non parasitées élevées sur “81–327” avaient un cycle de développement beaucoup plus long et un taux de mortalité beaucoup plus élevé que les larves non parasitées élevées comparativement sur feuilles de “Ransom”. Par contre, les larves parasitées manifestaient une consommation accrue du feuillage des deux lignées de soja. Les larves parasitées élevées sur les feuilles de la variété résistante GAT “81–327” pesaient moins et produisaient moins également de parasites adultes.

     

Investigation of the infection process of macrophomina phaseolina on the surface of soybean roots using scanning electron microscopy

Sclerotial germination, hyphal growth pattern, and appressorial formation of the charcoal rot fungus, Macrophomina phaseolina (Tassi) Goid. on the surface of soybean roots, Glycine max (L.) Merrill was observed using scanning electron microscopy. Sclerotial germination is followed by a hyphal growth pattern which does not appear to be associated with any specific structural feature on the corrugated root surface. Appressoria are produced on the root surface at the tips of both primary hyphae and side branches within three days after inoculation.     

Sex-based divergence in head shape and diet in the Eastern lubber grasshopper (Romalea microptera)

Biologists are becoming increasingly aware of sex-based differences in ecologically important traits (locomotor performance, feeding morphology, thermoregulatory behavior). Yet, the overwhelming majority of these studies have been performed on vertebrates, despite often striking examples of sexual size dimorphism among the insects. Here, I tested whether adult male and female Eastern lubber grasshoppers differ in size/shape and feeding ecology. The morphological data clearly showed sex-based differences in several aspects of head and body size, with females being significantly larger in all aspects. Moreover, the sexes also differed in two aspects of size-adjusted morphology: head width and pronotum width, with females having relatively wider heads and thoraxes than males. Multiple regression analysis indicated that width of consumed foliage was positively related to pronotum width and foliage thickness was positively related to pronotum width, head width, and size-adjusted head width. Females consumed wider and thicker foliage (primarily smooth cord grass, Spartina alterniflora) than males, which most frequently consumed the narrow-leafed forb hemp sesbania (Sesbania macrocarpa). Therefore, the sex-based differences in size and shape in this grasshopper are correlated with differences in consumed foliage shape.     

Activity of rubidium and cesium in soybean looper (Lepidoptera: Noctuidae): insect feeding on cotton and soybean measured by elemental markers

Uptake and translocation of the elemental markers rubidium (Rb) and cesium (Cs) within adult soybean looper, Pseudoplusia includens (Walker), were determined using atomic absorption spectrophotometry in the laboratory in various feeding and mating treatments. Neonates were tested to determine marker transfer from male and female adults fed rubidium chloride (RbCl)-treated artificial nectar, cesium chloride (CsCI)-treated artificial nectar, or both. All females contained detectable levels of Rb, Cs, or both, which were obtained either through direct feeding or via spermatophores. Rubidium was present in females at significantly greater levels than Cs. No significant differences in Rb levels were observed between feeding or spermatophore acquisitions. Most neonates had significantly higher levels of Rb than Cs. In a field cage study to evaluate adult feeding and oviposition behavior on blooming cotton and blooming soybean treated with RbCl and CsCl, respectively, more eggs contained Rb than Cs, indicating greater feeding on cotton nectar than soybean nectar, regardless of the host plant upon which eggs were laid. Females laid more eggs on blooming soybean than on blooming cotton. Higher levels of Rb in cotton than Cs in soybean were recorded and may be attributed to initial elemental marker quantities available to the insects. This study provides the support for the generalized observations that soybean looper infestations in soybean can be related to feeding activities by adults in cotton.     

Growth and induction in food consumption of Helicoverpa armigera Hbn. (Lep., Noctuidae) larvae on chickpea, soybean, and maize diets

Laboratory studies were conducted to determine the effect of different artificial diets made of powdered seed materials of chickpea ( Cicer arietinum ), soybean ( Glycine max ), and maize ( Zea mays ) on the growth, consumption, and feeding preferences of Helicoverpa armigera larvae. Food consumption and growth of ultimate instar gram pod borer larvae were minimal on maize diet. The nutritive value of the soybean diet was higher, but the consumption rate of larvae was highest on chickpea diet compared with the other test diets. The growth of larvae was statistically equal on chickpea and soybean diets, in spite of differences in the consumption rate of these diets and their nutritive value. There appears to be a direct correlation between the quantity of the diets consumed and their nutritive value for growth of the larvae on chickpea and soybean diets. The lower nutritive value of chickpea diet is correlated with its higher intake by the larvae. Similarly, the lower consumption rate of larvae on soybean diet is correlated with its higher nutritive value. The diet on which the larvae were fed during earlier instars did not induce any feeding preference for that particular diet in the ultimate larval instar. The larvae consumed similar quantities of each of the three diets in their ultimate instar, irrespective of having fed on any of these diets during any preceding instars. However, induction in the quantitative consumption of food by the larvae was evident. The higher or lower consumption rate of diet by the larvae in the ultimate instar was influenced by their food during earlier instars. Hence the food consumption rate of larvae in the last instar appears to be set while feeding on a diet in the preceding instars.     

Combining cry1Ac with QTL alleles from PI 229358 to improve soybean resistance to lepidopteran pests

A QTL conditioning corn earworm resistance in soybean PI 229358 and asynthetic Bacillus thuringiensis cry1Ac transgene from therecurrent parent Jack-Bt were pyramided intoBC₂F₃ plants by marker-assisted selection. Segregatingindividuals were genotyped at SSR markers linked to an anitbiosis/antixenosisQTL on linkage group M, and were tested for the presence ofcry1Ac. Marker-assisted selection was used during andafter the two backcrosses to develop a series of BC₂F₃plants with or without the crylAc transgene and the QTLconditioning for resistance BC₂F₃ plants that werehomozygous for parental alleles at markers on LG M, and whicheither had or lacked cry1Ac, were assigned to one of fourpossible genotype classes. These plants were used in no-choice, detached leaffeeding bioassays with corn earworm and soybean looper larvae (Lepidoptera:Noctuidae) to evaluate the relative antibiosis in the different genotypeclasses. Resistance was measured as larval weight gain and degree of foliageconsumption. Few larvae of either species survived on leaves expressing theCry1Ac protein. Though not as great as the effect of Cry1Ac, the PI229358-derived LG M QTL also had a detrimental effect on larval weights of bothpest species, and on defoliation by corn earworm, but did not reduce defoliation bysoybean looper. Weights of soybean looper larvae fed foliage from transgenicplants with the PI-derived QTL were lower than those of larvae fed transgenictissue with the corresponding Jack chromosomal segment. This work demonstratesthe usefulness of SSRs for marker-assisted selection in soybean, and shows thatcombining transgene-and QTL-mediated resistance to lepidopteran pests may be aviable strategy for insect control.     

Deterrent effect of soybean meal on feeding of the silkworm, Bombyx mori

The occurrence of a factor in soybean which deters feeding of the silkworm was demonstrated. The deterrent was not extractable with ether or ethanol, but was extracted with 90% ethanol or hot water. Preliminary experiments showed that the deterrent was adsorbed on charcoal, but neither on activated alumina nor in a steam distillate. Autoclaving did not inactivate the deleterious effect. A crude extract of the deterrent showed a marked negative feeding response by including 0·4 mg/g of the dry diet.Inclusion of the crude extract in the diet retarded the growth of larvae, whereas larvae grew well when receiving the 90% ethanol-washed meal. Feeding response for various soybean meals and proteins were compared, and better larval growth has generally obtained when the feeding response was more positive. It is, however, inconclusive whether or not the deleterious principle possesses some physiologically toxic effect.The feeding behaviour of newly hatched larvae was observed in the presence of favourable and/or unfavourable diets, and a brief discussion is made concerning the feeding behaviour of this insect.     

In-vitro Assays of Meloidogyne incognita and Heterodera glycines for Detection of Nematode-antagonistic Fungal Compounds

In-vitro methods were developed to test fungi for production of metabolites affecting nematode egg hatch and mobility of second-stage juveniles. Separate assays were developed for two nematodes: root-knot nematode (Meloidogyne incognita) and soybean cyst nematode (Heterodera glycines). For egg hatch to be successfully assayed, eggs must first be surface-disinfested to avoid the confounding effects of incidental microbial growth facilitated by the fungal culture medium. Sodium hypochlorite was more effective than chlorhexidine diacetate or formaldehyde solutions at surface-disinfesting soybean cyst nematode eggs from greenhouse cultures. Subsequent rinsing with sodium thiosulfate to remove residual chlorine from disinfested eggs did not improve either soybean cyst nematode hatch or juvenile mobility. Soybean cyst nematode hatch in all culture media was lower than in water. Sodium hypochlorite was also used to surface-disinfest root-knot nematode eggs. In contrast to soybean cyst nematode hatch, root-knot nematode hatch was higher in potato dextrose broth medium than in water. Broth of the fungus Fusarium equiseti inhibited root-knot nematode egg hatch and was investigated in more detail. Broth extract and its chemical fractions not only inhibited egg hatch but also immobilized second-stage juveniles that did hatch, confirming that the fungus secretes nematode-antagonistic metabolites.     

Factors affecting oral regurgitation by larval spruce budworm

This study evaluated factors that influence the regurgitation behaviour of sixth instar spruce budworm, Choristoneura fumiferana Clemens (Lepidoptera: Tortricidae), reared on balsam fir, Abies balsamea (L.) Mill. (Pinaceae), under various experimental conditions in the laboratory. Upon physical disturbance, larvae discharged a median volume of regurgitant of 0.4 μl when fed and 1.6 μl when food‐deprived. Larvae deprived of food for 24 or 48 h disgorged more regurgitant than larvae feeding on balsam fir foliage, and the effect was consistent for laboratory‐reared and field‐collected larvae. The water content of the foliage fed upon by larvae had no immediate impact on the volume of regurgitant; following a 24‐h period of food deprivation, however, larvae that previously fed on fresh foliage discharged >2.5 times more regurgitant than larvae that previously fed on dry foliage. Self‐regulated regurgitation by larvae, measured using the number of regurgitant stains on filter paper, was >10 times higher when larvae had access to balsam fir foliage than when they were starved. The number of larvae confined inside the Petri dish (one or four individuals) had a relatively small effect on regurgitation. Larvae were deterred from feeding when balsam fir needles were entirely covered with regurgitant, but not when only a portion of the foliage was treated. These results suggest that the regurgitant does not serve as resource marking or spacing pheromone. The high level of regurgitation by larvae after contact with ants suggests that the regurgitant has evolved in part as a defence mechanism against natural enemies.     

Effects of feeding by larvae of Phaedon cochleariae (F.) and Plutella maculipennis (Curt.) on the yield of radish and turnip plants

Different numbers of larvae of the beetle Phaedon cochleariae (F.) and the moth Plutella maculipennis (Curt.) were fed on the leaves of turnip plants (variety Early Milan White) and radish (variety French Breakfast) growing in a constant-environment room. Turnips grew more slowly than radish, were less affected by insect feeding and were affected more by Phaedon than by Plutella. Phaedon larvae severed leaf veins and rasped the leaf surface, thus killing more leaf tissue by desiccation than they ate. They remained on and greatly damaged the older leaves and their feeding reduced yield. Plutella larvae fed on leaves of all ages, which they ate cleanly, leaving the veins. They pupated sooner than Phaedon and did less damage to older leaves, which grew larger and lived longer than corresponding leaves on intact plants. This compensatory growth by turnip prevented loss of yield and may have increased it, as indicated by dry weight of the roots. Both species of insect decreased the yield of radish similarly. Loss of yield of turnip caused by Phaedon or of radish caused by both species of insects was negatively and linearly proportional to the number of larvae that fed on the leaves.     

The Rhizoctonia-Meloidogyne Disease Complex in Flue-cured Tobacco

If Meloidogyne incognita preceded Rhizoctonia solani by 10 days or 21 days in roots of greenhouse-grown tobacco plants, root rot was more extensive than when the nematode and fungus were introduced either simultaneously or separately or when R. solani was added after artificial wounding. Histological examination of galled roots 72 days after inoculation with R. solani revealed extensive fungal colonization in the root-knot susceptible cultivar ''Dixie Bright 101'' when M. incognita preceded R. solani by 21 days. R. solani, normally nonpathogenic on mature tobacco roots, may cause severe losses when present with well-established root-knot nematode infections.     

Effect of nematode Panagrellus redivivus density on growth, survival, feed consumption and carcass composition of bighead carp Aristichthys nobilis (Richardson) larvae

The study aimed to determine the optimum density of free‐living nematodes in feeding bighead carp, Aristichthys nobilis, larvae. In the first experiment, carp stocked at 25 larvae L^?1 were fed varying levels of nematodes (50, 75, 100, 125 and 150 per ml) twice a day for 21 days from the start of exogenous feeding. Final body weight was significantly higher (P < 0.05) in larvae fed 125 and 150 nematodes per ml than in those fed 50 and 75 per ml, but survival was low (61.8 and 63.6%, respectively). Survival rate was highest in larvae fed 100 nematodes ml^?1 (81.3%). Carcass analysis showed that larvae fed 125 and 150 nematodes ml^?1 had significantly lower body protein and higher body lipid than those fed other nematode densities. Carcass ash was similar for larvae fed 50–100 nematodes ml^?1 but it decreased significantly at the higher nematode densities. Carp larvae in a subsequent experiment were given 50, 75 and 100 nematodes ml^?1 per feeding. Newly hatched Artemia was the control feed. Nematode consumption and growth of the larvae were determined. Larvae were sampled at intervals of 2–4 days and the nematodes in the gut were counted and measured. At each nematode density, the number of nematodes present in the gut of the larvae increased significantly with time. At each sampling day, the number of nematodes in the gut did not differ significantly among treatments (P > 0.05) although it tended to increase with nematode density at day 2 and day 4 but decrease at day 7 onward. The carp larvae consumed significantly shorter nematodes on day 2 and day 4 than on the succeeding sampling days regardless of nematode density. However, the length of nematodes in the gut of the larvae did not differ significantly among the nematode densities. The final body weight of larvae increased with increasing nematode density. The body weight of larvae fed 100 nematodes ml^?1 did not differ significantly from that of larvae given Artemia nauplii. Results show that bighead carp larvae should be fed 100 free‐living nematodes per ml at each feeding time.     

Biology and preliminary host range assessment of two potential kudzu biological control agents

Two insect species from China, Gonioctena tredecimmaculata (Jacoby) (Coleoptera: Chrysomelidae) and Ornatalcides (Mesalcidodes) trifidus (Pascoe) (Coleoptera: Curculionidae), were studied in quarantine in the United States as potential biological control agents for kudzu, Pueraria montana variety lobata (Willd.) Maesen and S. Almeida. Adults of G. tredecimmaculata were ovoviviparous and reproduced throughout the summer, producing offspring that had an obligate adult diapause. In no-choice tests, adult and larval G. tredecimmaculata rejected most of the plant species tested, but consumed foliage and completed their life cycle on soybean (Glycine max L. Merr.) and on a native woodland plant, hog-peanut (Amphicarpaea bracteata L. Fernald), which are in the same subtribe as kudzu (Glycininae). Insects showed similar responses to field- and greenhouse-grown soybean and kudzu foliage, despite measurable differences in leaf traits: field-grown foliage of both plants had greater leaf toughness, higher total carbon content, higher trichome density, and lower water content than greenhouse foliage. O. trifidus adults also rejected most of the plants tested but fed on and severely damaged potted soybean and hog-peanut plants in addition to kudzu. Further tests in China are needed to determine whether these species will accept nontarget host plants under open-field conditions.     

Insect responses to plant water deficits. I. Effect of water deficits in soybean plants on the feeding preference of Mexican bean beetle larvae

Abstract. 1. We examined the preference of larvae of the Mexican bean beetle, Epilachna varivestis Mulsant (Coleoptera: Coccinellidae), for foliage of soybean ( Glycine max [L.] Merr.) grown under several levels of water deficit. Third instar larvae were exposed simultaneously to excised foliage from plants that were either well-watered (control) or had experienced water deficits (treatment).
2. Water-deficient plants were re-watered 12 h prior to initiating feeding trials to eliminate physical differences between control and treatment foliage such as leaf water potential, diffusive resistance, relative water content, and foliage toughness.
3. Examination of the free amino acid contents of re-watered and excised foliage indicated that amino acid concentrations increased markedly in foliage grown under water deficits, and that this increase persisted during the preference tests.
4. Larvae preferred control foliage, but shifted preference to treatment foliage under mild water deficits. When the leaf water potential of water-deficient treatment foliage was lower than – 1.13 MPa or when it was more than 0.5 MPa lower than that of control foliage, larvae preferred to feed on foliage from well-watered control plants.
5. The expression of preference for well-watered control foliage was coincident with increases in the concentrations of total free amino acids and individual free amino acids in the water-deficient treatment foliage.
6. These results are inconsistent with White's (1974) hypothesis because Mexican bean beetle larvae avoid plants grown under water deficits that have increased concentrations of free amino acids.     

Expression of soybean proteinase inhibitors in transgenic sugarcane plants: effects on natural defense against Diatraea saccharalis

The introduction and expression of proteinase inhibitor encoding genes into sugarcane (Saccharum officinarum L.) genome is an interesting strategy for conferring partial resistance to the sugarcane borer Diatraea saccharalis (Lepidoptera: Crambidae), the major insect pest of sugarcane in Brazil. To investigate the role of soybean (Glycine max L.) Kunitz trypsin inhibitor (SKTI) and soybean Bowman–Birk inhibitor (SBBI) in the control of D. saccharalis, the cDNAs encoding these proteinase inhibitors were placed under the control of the maize ubiquitin promoter (Ubi-1), and introduced into sugarcane callus using particle bombardment. Putative transgenic plants were initially identified after regeneration from callus growing in the presence of 30 mg l^–1 geneticin, while molecular characterization of transgenic plants revealed that both genes were incorporated into the sugarcane genome and expressed. We also carried out insect feeding trials using D. saccharalis neonate larvae and leaf tissue excised from propagated transgenic and untransformed plants, and found that the growth of larvae feeding on leaf tissue from transgenic plants containing BBI and Kunitz inhibitors was significantly retarded as compared to larvae fed on leaf tissue from untransformed plants. In greenhouse trials with transgenic sugarcane plants infested with D. saccharalis neonates, we found that these plants still presented the ‘dead heart’ symptom typically observed in susceptible plants in the field, suggesting that the retardation of the growth of D. saccharalis observed in the laboratory-based feeding trials was not sufficient to prevent this type of damage.     

The tobacco Cel7 gene promoter is auxin-responsive and locally induced in nematode feeding sites of heterologous plants

Emerging evidence suggests that plant cell-wall-modifying enzymes induced by root-parasitic nematodes play important roles in feeding cell formation. We previously identified a tobacco endo-β-1,4-glucanase (cellulase) gene, NtCel7 , that was strongly induced in both root-knot and cyst nematode feeding cells. To characterize further the developmental and nematode-responsive regulation of NtCel7 , we isolated the NtCel7 promoter and analysed its expression over a time course of nematode infection and in response to auxin, gibberellin, ethylene and sucrose in soybean and tomato hairy roots and in Arabidopsis containing the NtCel7 promoter fused to the β-glucuronidase (GUS) reporter gene. Histochemical analyses of transgenic plant materials revealed that the NtCel7 promoter exhibited a unique organ-specific expression pattern during plant development suggestive of important roles for NtCel7 in both vegetative and reproductive growth. In all plant species tested, strong GUS expression was observed in root tips and lateral root primordia of uninfected roots with weaker expression in the root vasculature. Further analyses of transgenic Arabidopsis plants revealed expression in shoot and root meristems and the vasculature of most organs during plant development. We also determined that the NtCel7 promoter was induced by auxin, but not gibberellin, ethylene or sucrose. Moreover, strong GUS activity was observed in both cyst and root-knot nematode-induced feeding sites in transgenic roots of soybean, tomato and Arabidopsis. The conserved developmental and nematode-responsive expression of the NtCel7 promoter in heterologous plants indicates that motifs of this regulatory element play a fundamental role in regulating NtCel7 gene expression within nematode feeding sites and that this regulation may be mediated by auxin.     

Lotus japonicus: a new model to study root-parasitic nematodes

Sedentary plant-parasitic nematodes engage in complex interactions, and induce specialized feeding structures by redirecting plant developmental pathways, and parallels have been observed with rhizobial nodule development on legumes. A model legume would greatly facilitate a better understanding of the differences between parasitic (nematode) and mutualistic (rhizobia and mycorrhizae) symbioses, and we have developed Lotus japonicus as such a model. Conditions for efficient parasitism by root-knot nematode (Meloidogyne spp.) of the widely used Lotus "Gifu" ecotype were established. Features of Lotus biology, such as thin and translucent roots, proved ideal for monitoring the progress of nematode infection both on live specimens and post-staining. We examined L. japonicus mutants with nodulation phenotypes. One, har1, which is a hypernodulated mutant defective in a CLAVATA1-like receptor kinase gene, was found to be hyperinfected by M. incognita. However, another hypernodulated Lotus mutant exhibited the same level of M. incognita infection as wild-type plants. We also established conditions for infection of Lotus by soybean cyst nematode (Heterodera glycines). In contrast to the response to root-knot nematode, the Gifu ecotype is resistant to H. glycines, and elicits a hypersensitive response. This pattern of resistance recapitulates that seen on nematode-resistant soybean plants. We conclude that L. japonicus is a powerful model legume for studying compatible and incompatible plant-nematode interactions.     

Bacillus thuringiensis cry3Ca1 protein is toxic to the Colorado potato beetle, Leptinotarsa decemlineata (Say)

We expressed the wild-type cry3Aa3 and cry3Ca1 Bacillus thuringiensis genes, which code for insecticidal proteins, in an Escherichia coli expression system. Highly purified preparations of the soluble delta-endotoxins were used to perform comparative bioassays with third-instar larvae of the Colorado potato beetle (CPB). Acute mortality data showed that Cry3Ca1 (LD(50) = 320.1 ng) was 2-fold more toxic than Cry3Aa3 (LD(50) = 672.9 ng). We also compared the chronic effects of sublethal doses of these toxins by measuring the consumption of untreated foliage and monitoring survival and development for 6 days after intoxication. No significant additional mortality was recorded, but we found that surviving larvae fed Cry3Ca1 consumed foliage at a slower rate than the larvae fed Cry3Aa3, suggesting more damage to their digestive epithelium. This study, the first assessment of the toxicity of cry3Ca1 in third-instar CPB, suggests cry3Ca1 will prove useful for the control of this important insect pest.