Plant growth-promoting rhizobacteria modulate induced corn defense against Spodoptera litura (Lepidoptera: Noctuidae).

Common cutworm, Spodoptera litura is an important pest of corn causing significant crop yield loss. Synthetic insecticides have mostly been used to combat this pest, raising human and environmental health concerns. Plant-growth promoting rhizobacteria (PGPR) could compensate for or augment the harmful effects of agrochemicals. Herein, we aimed to assess whether PGPR-induced defenses in corn plants impact the host-plant selection behavior of S. litura. Headspace volatile organic compounds (VOCs) were analyzed using Gas chromatography-mass spectrometry (GC-MS). Larvae fed inoculated corn exhibited lower weights and RGR than non-inoculated plants. Under choice experiments, PGPR-treated plants significantly reduced percentage leaf damage area and oviposition rate compared to untreated plants. VOC ratio emission varied significantly between control and PGPR treatments, which, in part, explains feeding and oviposition deterrence in PGPR-treated plants. The results demonstrate that PGPR inoculation can enhance corn resistance to S. litura, making it a promising candidate for crop protection strategies.

The effect of attractive toxic sugar bait on the Asian tiger mosquito, Aedes albopictus (Diptera: Culicidae) in community farms in Northern Taiwan.

Attractive toxic sugar baits (ATSBs) lure mosquitoes to feed on the baits and subsequently killed them. We investigated the effects of a boric acid-containing ATSB on the population of Aedes albopictus at 48 h exposure and assessed the field effectiveness on this ATSB on two types of community farms in New Taipei City, Taiwan, including isolated ATSB farms and nonisolated ATSB farms. The result showed that mosquitoes exposed to the ATSB solution for 48 h were killed within 7 d under laboratory conditions. Exposure of female and male mosquitoes to ATSB resulted in mean survival times ranging from 52 to 62 h and 30 to 48 h, respectively. For field efficacy test, on isolated ATSB farms, a significant reduction of ovitrap density index (ODI) up to 24 % was noted after the replacement frequency was increased to every 2 weeks. However, the intervention efficacy on nonisolated ATSB farms had mixed results. The ODI significantly reduced by 21.4 % and 6.9 % on the nonisolated ATSB Chongmin and Nanjing farms, respectively, when bait replacement was done every 2 weeks instead of every 3 weeks. By contrast, the ODI on the nonisolated ATSB Yongchang farms increased significantly, irrespectively of the bait replacement frequency. Nevertheless, the total number of eggs trapped on all ATSB farms exhibited a concave curve pattern; while the mosquito population on non-ATSB control farms continued to increase over time. In conclusion, deploying simple ATSB stations containing boric acid is a practical approach for integrated vector management programs.

Elucidating the Fitness of a Dead-End Trap Crop Strategy against the Tomato Fruitworm, Helicoverpa armigera.

Solanum viarum has been proposed as a potential dead-end trap crop for the management of Helicoverpa armigera because of its unsuitability for larval growth and survival despite being overwhelmingly preferred for oviposition. This study delved into the different S. viarum accessions for ovipositional preference and non-suitability for larval growth and survival of H. armigera. Besides, foliage trichomes, acylsugars, and phenolic content of S. viarum plants were assessed and compared with tomato. Since there is no significant variation in the ovipositional preference and larval performance of H. armigera, our result revealed that all those evaluated accessions of S. viarum have the potential to be used as a dead-end trap crop for the management of H. armigera. However, significant variation among the S. viarum accessions in terms of H. armigera oviposition was also evident in a no-choice experiment. Because of high-density glandular trichomes, acylsugars, and phenolic content, S. viarum significantly impaired H. armigera larval growth and survival compared to the tomato. Hence, our study elucidated that the S. viarum plant fits with the criteria for dead-end trap crop, and has the potential as a dead-end trap crop for the H. armigera, which needs to be tested under large, open-field conditions.

Thermal effect on the fecundity and longevity of Bactrocera dorsalis adults and their improved oviposition model.

The oriental fruit fly, Bactrocera dorsalis, is a destructive polyphagous pest that causes damage to various fruit crops, and their distribution is currently expanding worldwide. Temperature is an important abiotic factor that influences insect population dynamics and distribution by affecting their survival, development, and reproduction. We examined the fecundity, pre-oviposition and oviposition periods, and longevity of adult B. dorsalis at various constant temperatures ranging from13°C to 35°C. The longevity of female B. dorsalis ranged from 116.8 days (18.8°C) to 22.4 days (34.9°C), and the maximum fecundity per female was 1,684 eggs at 28.1°C. Females were only able to lay eggs at 16.7°C to 34.9°C, and both the pre-oviposition and oviposition periods were different depending on the temperature. We modeled female reproduction in two oviposition models (OMs): 1) the current model developed by Kim and Lee, an OM composed of a fecundity model, age-specific survival model, and age-specific cumulative oviposition rate model, and 2) a two-phase OM modified the logic structure of the current model by separating pre-oviposition, so that oviposition was estimated with the female in oviposition phase who had complete pre-oviposition phase. The results of the two-phase OM provided more realistic outputs at lower and higher temperatures than those of the current model. We discussed the usefulness of the two-phase OM for the reproduction of insects with long pre-oviposition periods.

Effects of Feeding Adults of Hermetia illucens (Diptera: Stratiomyidae) on Longevity, Oviposition, and Egg Hatchability: Insights Into Optimizing Egg Production.

Larvae of the black soldier fly, Hermetia illucens (L.), have been widely studied for their capacity of generating value-added products through waste bioconversion. Several efforts have been made towards optimization of rearing methods of the larval stages. Despite this, less information regarding the feeding behavior of adults and its effects on life parameters is available. We studied the impacts of subjecting adults to four diets: no diet (control); drinking water (water); a mix of sugar, bacteriological peptone, and milk powder (milk); and agar with sugar (agar). In total five replicates with 50 females and 50 males per treatment were performed. Oviposition and mortality were recorded daily. Additionally, egg hatchability and number of eggs per mass were measured. Results from this study indicate that the amount of eggs was 3 times higher for diets containing a protein source. Furthermore, milk treatment increased the oviposition period by 10 d compared with that of the standard water treatment. No significant difference was found for male longevity; however, females fed with milk diet lived 5 d longer than the control group. Egg hatchability ranged 70-85%, but was not significantly different across treatments. In terms of egg production for both industrial and research purposes, we suggest using a protein-rich diet to maximize oviposition and longevity parameters as adults do benefit from feeding.

The roles of jasmonate signalling in nitrogen uptake and allocation in rice (Oryza sativa L.).

Herbivore damage by chewing insects activates jasmonate (JA) signalling that can elicit systemic defense responses in rice. Few details are known, however, concerning the mechanism, whereby JA signalling modulates nutrient status in rice in response to herbivory. (15 NH4 )2 SO4 labelling experiments, proteomic surveys, and RT-qPCR analyses were used to identify the roles of JA signalling in nitrogen (N) uptake and allocation in rice plants. Exogenous applications of methyl jasmonate (MeJA) to rice seedlings led to significantly reduced N uptake in roots and reduced translocation of recently-absorbed 15 N from roots to leaves, likely occurring as a result of down-regulation of glutamine synthetase cytosolic isozyme 1-2 and ferredoxin-nitrite reductase. Shoot MeJA treatment resulted in a remobilization of endogenous unlabelled 14 N from leaves to roots, and root MeJA treatment also increased 14 N accumulation in roots but did not affect 14 N accumulation in leaves of rice. Additionally, proteomic and RT-qPCR experiments showed that JA-mediated plastid disassembly and dehydrogenases GDH2 up-regulation contribute to N release in leaves to support production of defensive proteins/compounds under N-limited condition. Collectively, our results indicate that JA signalling mediates large-scale systemic changes in N uptake and allocation in rice plants.

Subtropical Tritrophic Interactions Under Elevated CO2 and Temperature Conditions.

The effects of climate change and extreme weather conditions on plants and animals have been documented extensively. However, the possible effects of these factors on plant-insect interactions in subtropical regions are relatively unexplored. The present study investigated the consequences of elevated CO2 and temperature on a tritrophic system (plant-insect-parasitoid) in subtropical regions. The experimental conditions were as follows: ambient CO2, 500 ppm; elevated CO2, 1,000 ppm; ambient temperature, 24/21°C (day/night); and elevated temperature, 29/26°C (day/night). Brassica oleracea var. italica foliar primary metabolites were quantified 6 wk after germination and insect feeding bioassays were subsequently conducted. Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae) larvae were fed directly on these plants until pupal development. In addition, the second instar S. litura larvae were exposed to the parasitoid Snellenius manilae (Ashmead) (Hymenoptera: Braconidae) under the same plant treatment conditions. The results suggested that elevated CO2 has a major influence on plant performance and foliar quality. Elevated CO2 also affected the leaf area, foliar fresh and dry weights, and total nitrogen and carbohydrate contents. Elevated temperature reduced the larval development time and increased the growth rate of S. litura. Sn. manilae had a higher parasitism rate and shorter development time at elevated temperature compared with ambient temperature. These results suggested that the dynamic and communal structure of S. litura and its parasitoids requires comprehensive evaluation in terms of the changes in nutritional quality (bottom-up control) caused by the interactive effects of CO2 and temperature.

Degradation Capacity and Diapause Effects on Oviposition of Hermetia illucens (Diptera: Stratiomyidae).

Although well known for its organic waste decomposing capability, much of the biology of Hermetia illucens (L.) (Diptera: Stratiomyidae) remains unknown, including details involving its diapause. The present study provides a better understanding of the effects of diapause on the fecundity and longevity of H. illucens. The daily degradation rates (dry weight of the uneaten residue) of a H. illucens cohort were also evaluated. Data were collected and analyzed based on the age-stage, two-sex life table. The intrinsic rate of increase (r), finite rate of increase (λ), net reproduction rate (R0), and mean generation time (T) were 0.0498 (d-1), 1.0511 (d-1), 118.3 offspring, and 95.8 d, respectively. The maximum net maternity was 22.5 eggs after 88 d. Only 12 females out of 22 were able to successfully oviposit. The number of eggs produced per female ranged from 508 to 1,047. Degradation and consumption occurred during each of the 23 d until all larvae developed into the prepupal stage. The age-stage net consumption rate (Bxj) dropped at day 11 (1.05 mg) and then reached its highest level at day 14 (1.72 mg). The mean degradation rate was 26.69 mg and the total degradation and consumption was 1,921.52 mg. Linking life table data and degradation rates provides the necessary data for predicting a population's growth and its degradation capacity. Results of this study demonstrated the importance of adding moisture during the prepupal stage. This information will provide a better understanding for an implementation program using H. illucens as a biodegrading agent of organic waste matter.

Survival and Development of Hermetia illucens (Diptera: Stratiomyidae): A Biodegradation Agent of Organic Waste.

The black soldier fly, Hermetia illucens (L.) (Diptera: Stratiomyidae), was reared on artificial diet (wheat bran and chicken feed) in the laboratory at 28ºC (immature stages) and under a greenhouse set at 28ºC (adults). Data were collected and analyzed based on an age-stage, two-sex life table. The intrinsic rate of increase (r), finite rate of increase (λ), net reproduction rate (R0), and mean generation time (T) were 0.0759 (d-1), 1.0759 (d-1), 68.225 offspring, and 55.635 d, respectively. The maximum reproductive value of females occurred at 54 d. Only six females out of 21 were able to successfully oviposit. The number of eggs laid per female ranged from 236 to a maximum of 1,088 eggs. We demonstrated that first-instar larvae of H. illucens are more susceptible to perishing when reared under artificial diet than are later instars.

La mosca soldado negro, Hermetia illucens (L.) (Diptera: Stratiomyidae), fue alimentada en una dieta artificial (salvado de trigo y alimento para pollos) en el laboratorio a 28ºC (estados inmaduros) y en un invernadero a 28ºC (adultos). Los datos fueron recopilados y analizados en base a la tabla de vida de ambos sexos, edad y etapa. La tasa intrínseca de crecimiento (r), tasa finita de crecimiento (λ), la tasa neta de reproducción (R0) y el tiempo medio generacional (T) fueron 0.0759 (d), 1.0759 (d), 68.225 crías, y 55.635 (d), respectivamente. El valor reproductivo máximo de las hembras se produjo a los 54 días. Sólo 6 de las 21 hembras fueron capaces de poner huevos con éxito. El número de huevos por hembra varió de 236 a un máximo de 1088 huevos. Hemos demostrado que cuando han sido criados en una dieta artificial, las larvas de H. illucens durante el primer instar son más susceptibles a perecer que los instares posteriores.

Temperature-dependent demography of Aulacaspis yasumatsui (Hemiptera: Diaspididae).

Aulacaspis yasumatsui Takagi continues to threaten the extinction of the endemic and endangered Cycas taitungensis (Shen et al.) in Taiwan. Failure to understand its population demographic parameters in detail will continue to hinder the success of pest management practices. An in-depth knowledge of the development, survival, and fecundity of A. yasumatsui under different environmental conditions is necessary to understand its' population growth. The demography of A. yasumatsui was studied in the laboratory based on the age-stage, two-sex life table at 20, 23, 25, 28, and 31 degrees C, 70% relative humidity, and a photoperiod of 16:8 (L:D) h. The intrinsic rate of increase (r) under these temperatures was 0.06, 0.07, 0.09, 0.10, and 0.08 d(-1), respectively. The net reproductive rate (R0) was 46.27, 47.78, 69.50, 96.08, and 56.65 offsprings per individual and the mean generation time (T) was 65.60, 55.81, 47.82, 44.15, and 51.42 d, respectively. A. yasumatsui does well at warmer temperatures (25-28 degrees C); however, its performance is disrupted at lower temperatures. This study provides insight on how to minimize growth and destruction of A. yasumatsui and conservation of Cy. taitungensis; new cycad reserves should be set up in cooler areas in Taiwan.

Temperature-dependent demography of Chilades pandava peripatria (Lepidoptera: Lycaenidae).

Chilades pandava peripatria Hsu and its host plant Cycas taitungensis Shen, Hill, Tsou & Chen are both endemic species to Taiwan. Ch. pandava peripatria has a specific association with buds and soft leaves of cycad plants. The introduced species, Cy. revoluta, have prolonged budding periods and extensive auxiliary buds that extensively contribute to the outbreak of Ch. pandava peripatria. An in-depth knowledge of the development, survival, and fecundity of Ch. pandava peripatria under different environmental conditions is necessary to understand the population growth of Ch. pandava peripatria. The demography of Ch. pandava peripatria was studied based on the age-stage, two-sex life table at 20, 23, 25, 28, and 31 degrees C, 70% RH, and a photoperiod of 16:8 (L:D) h under laboratory conditions. Ch. pandava peripatria completed its development under tested temperatures but did not produce offsprings at 23 degrees C. Because of the high egg mortality at 20 degrees C, the data at this given temperature were excluded from this study. The intrinsic rate of increase (r) under these tested temperatures was 0.1846, 0.2919, and 0.1412 d(-1), respectively. The net reproductive rate (H(o)) was 165.47, 262.32, and 56.68 offsprings per individual and the mean generation time (T) was 27.72, 19.10, and 28.67 d, respectively. Our results indicated that Ch. pandava peripatria is highly adaptable to environments where temperature ranges from 25 to 31 degrees C.

Spatial variation in foliar chemicals within radish (Raphanus sativus) plants and their effects on performance of Spodoptera litura.

Foliar chemicals are variable within a plant and this may affect herbivore feeding preference. This study was carried out to quantify concentrations of primary (nitrogen, water, and total nonstructural carbohydrates) and secondary substances (sinigrin) in young and old leaves of Raphanus sativus L. and to evaluate performance and survival of a generalist herbivore Spodoptera litura F. feeding on them. Forty to 50-d-old R. sativus plants were used in both foliar chemical analysis and insect performance bioassays. Leaves located on the third to the sixth node from the base of the plant were defined as old leaves and the remaining leaves (from seventh node to the plant apex) of the plant were referred as young leaves in this study. All foliar chemicals except water differed significantly between young and old leaves. Moreover, young leaves were more nutritious but much more defended, based on sinigrin content, against S. litura than old leaves. Performance and survival of S. litura were reduced on young leaves as compared with old leaves. Male and female larval duration only differed significantly on young leaves. Female larval development time was longer than male development time on young leaves, but not on older leaves. Therefore, this study revealed that defenses in young leaves have differential effects upon male and female S. litura.

Effects of irradiation on Planococcus minor (Hemiptera: Pseudococcidae).

Irradiation has been recognized and endorsed as a potential phytosanitary measure that could be an alternative to current quarantine treatments. Dosages of 50, 100, 150, 200, and 250 Gy were used to irradiate three different life stages (eggs, immatures, and adults) of Planococcus minor (Maskell) (Hemiptera: Pseudococcidae), focusing on females due to its parthenogenesis ability, with an aim to find the most tolerant stage and the most optimal dose to control P. minor. Cobalt 60 was the source of irradiation used. Irradiation of 150-250 Gy has a significant effect on all life stages of P. minor, decreasing its survival rate, percentage of adult reproduction, oviposition, and fertility rate. The adult was the most tolerant life stage in both mortality and fertility rate. All the different irradiated target life stage groups oviposited eggs, but none of the F2 eggs hatched at the most optimal dosage of 150-250 Gy.

Soil fertility management and pest responses: a comparison of organic and synthetic fertilization.

The objective of this study was to assess the effect of fertilization (organic or synthetic) and cabbage, Brassica oleracea L., cultivars ('K-Y cross' and 'Summer Summit') on the chemistry of cabbage and on the responses of a cabbage specialist Pieris rapae crucivora Boisduval. Cabbages were grown from seeds in the greenhouse with either organic, synthetic, or no fertilizer treatments. Trials of ovipositional preference and larval feeding were conducted to evaluate the effect of foliage quality on insect responses. In addition, the foliar chemistry (water, nitrogen, total nonstructural carbohydrates, sinigrin, and anthocyanin) was measured during the insect bioassays. The results indicated that butterflies preferred to lay eggs on foliage of fertilized plants. The larvae grew faster on plants fertilized with synthetic fertilizer, but there was no evidence that contents of sinigrin delayed the developmental time of the larvae. However, plants that received organic fertilizer had higher biomass. In summary, the results of this study suggested that proper organic treatment can increase a plant's biomass production and may have a lower pest occurrence.

Responses of Helicoverpa armigera to tomato plants previously infected by ToMV or damaged by H. armigera.

We report the comparative inducing effects of a phytopathogen and a herbivorous arthropod on the performance of an herbivore. Tomato, Lycopersicon esculentum Mill., was used as the test plant, and tomato mosaic virus (ToMV) and corn earworm, Helicoverpa armigera Hübner, were used as the phytopathogen and herbivore, respectively. There were decreases in the efficiency of conversion of ingested food and efficiency of conversion of digested food when H. armigera was reared on tomato plants that had been previously inoculated with ToMV. However, virus inoculation did not affect feeding or oviposition preferences by H. armigera. In contrast, approximate digestibility, total consumption, relative growth rate, and relative consumption rate were lower for fourth-instar H. armigera that fed on plants previously damaged by the same herbivore. Feeding and oviposition were both deterred for H. armigera that fed on previously damaged plants. The duration of development of H. armigera was also prolonged under this treatment. Infection by ToMV and feeding damage by H. armigera increased the host plant's peroxidase and polyphenol oxidase activity, respectively, suggesting that the performance of H. armigera may be affected by the induced phytochemistry of the host plant. Overall, this study indicated that, in general, insect damage has a stronger effect than ToMV infection on plant chemistry and, subsequently, on the performance of H. armigera.

Shifts in developmental diet breadth of Lymantria xylina (Lepidoptera: Lymantriidae).

The moth Lymantria xylina Swinhoe (1903) (Lepidoptera: Lymantriidae) is a major defoliator of hardwood and fruit trees in Taiwan. Although the plants identified as host plants of L. xylina usually refer to plants used as food or as shelter, most of the host plant identifications have not considered the role of these hosts on larval development. This study investigated various instars feeding on different plants to assess the developmental diet breath of L. xylina. Forty-seven plant species, belonging to 25 families were used in feeding trials. Various bioassays, including first instar survival and long-term feeding trials, indicated the most suitable host plants for the different developmental stages. Results of the first instar survival trial indicated that first instars could survive only on 13 of the tested plant species. In addition, first instars could only successfully grow to pupa on seven of these 13 test plants species. To assess the developmental diet breath shifts of this moth, 38 plant species (excluding those nine plant species that the first instars did not feed upon) were fed to third and fifth instars in long-term feeding trials. Survival to pupa was noted on 12 and 13 test plant species for the third and fifth instars, respectively. In short, we found that the larvae performed differently when fed on various host plants and that the host plant range increased with the larval stage. Therefore, it is necessary to adjust the host plant range of this moth and to consider host plant breadth together with the developmental stages of caterpillars.

Performance of Lymantria xylina (Lepidoptera: Lymantriidae) on artificial and host plant diets.

Lymantria xylina Swinhoe (Lepidoptera: Lymantriidae) is a serious defoliator of hardwood and fruit trees in Taiwan. The larvae of L. xylina feed on >63 species of host plants, belonging to 29 families. Because a large number of larvae are needed for the production of nucleopolyhedrosis virus (NPV) or other related studies, the development of a suitable artificial diet is very important for the mass rearing of this moth in the laboratory. In this study, eight artificial diets, modified from different formulas, and one host plant, Liquidambar formosana Hance, were used to feed L. xylina caterpillars. Through various bioassays (first instar survival trial and long- and short-term feeding trials), the most suitable diet for the L. xylina was selected by performance comparisons with L. formosana. After the first instar survival trial, two of the diets were discarded, because no larva survived on these diets. The results of the long-term feeding trial indicated that the larvae grew successfully on only three kinds of artificial diet. Finally, results of the short-term feeding trial revealed that a diet (diet A), modified from the gypsy moth, Lymantria dispar (L.), formula diet, was the most appropriate for the L. xylina. Larvae fed on diet A had better survival rate, pupal weight, adult size, efficiency of conversion, and relative growth rate than larvae fed on other diets; they did not grow as well as those fed on L. formosana, however, except for pupal and adult weight, and approximate digestibility. In summary, diet A was found to be the best of the artificial diets for the L. xylina and is suitable for mass rearing of this moth in the laboratory.

Ferredoxin from sweet pepper (Capsicum annuum L.) intensifying harpin(pss)-mediated hypersensitive response shows an enhanced production of active oxygen species (AOS).

The hypersensitive response (HR) is a form of cell death associated with plant resistance to pathogen infection. Harpin(pss), an elicitor from the bacterium Pseudomonas syringae pv. syringae, induces a HR in non-host plants. Previously, we reported an amphipathic protein from sweet pepper interfering with harpin(pss)-mediated HR. In this report, we isolated and characterized a cDNA clone encoded that amphipathic protein from sweet pepper. This protein is designated as PFLP (plant ferredoxin-like protein) by virtue of its high homology with plant ferredoxin protein containing an N-terminal signal peptide responsible for chloroplast targeting and a putative 2Fe-2S domain responsible for redox activity. Recombinant PFLP obtained from Escherichia coli was able to significantly increase active oxygen species (AOS) generation when mixed with harpin(pss) in tobacco suspension cells. It also showed enhanced HR when co-infiltrated with harpin(pss) in tobacco leaves. We used a transgenic tobacco suspension cells system that constitutively expresses the Pflp gene driven by the CaMV 35S promoter to study the function of PFLP in enhancing harpin(pss)-mediated hypersensitive cell death in vivo. In response to harpin(pss), suspension cells derived from Pflp transgenic tobacco showed a significant increase both in the generation of AOS and in cell death as compared to the wild type. AOS inhibitors diphenylene iodonium chloride (DPI) and lanthanum chlorate (LaCl3) were used to study the involvement of AOS in harpin(pss)-induced cell death. Our results demonstrate enhanced generation of AOS is necessary to cause enhanced hypersensitive cell death in Pflp transgenic tobacco cells and it is plasma membrane-bound NADPH-oxidase-dependent. Sub-cellular localization studies showed that PFLP is present in the cytoplasm and chloroplast of Pflp transgenic tobacco cells, but only in the chloroplast, not in the cytoplasm, of wild-type tobacco cells. It is possible that PFLP can change the redox state of the cell upon harpin(pss) inoculation to increase AOS generation and hypersensitive cell death. Overall, this study will provide a new insight in the functional properties of ferredoxin in hypersensitive cell death.

Constitutive expression of hrap gene in transgenic tobacco plant enhances resistance against virulent bacterial pathogens by induction of a hypersensitive response.

Hypersensitive response-assisting protein (HRAP) has been previously reported as an amphipathic plant protein isolated from sweet pepper that intensifies the harpin(Pss)-mediated hypersensitive response (HR). The hrap gene has no appreciable similarity to any other known sequences, and its activity can be rapidly induced by incompatible pathogen infection. To assess the function of the hrap gene in plant disease resistance, the CaMV 35S promoter was used to express sweet pepper hrap in transgenic tobacco. Compared with wild-type tobacco, transgenic tobacco plants exhibit more sensitivity to harpin(Pss) and show resistance to virulent pathogens (Pseudomonas syringae pv. tabaci and Erwinia carotovora subsp. carotovora). This disease resistance of transgenic tobacco does not originate from a constitutive HR, because endogenous level of salicylic acid and hsr203J mRNA showed similarities in transgenic and wildtype tobacco under noninfected conditions. However, following a virulent pathogen infection in hrap transgenic tobacco, hsr203J was rapidly induced and a micro-HR necrosis was visualized by trypan blue staining in the infiltration area. Consequently, we suggest that the disease resistance of transgenic plants may result from the induction of a HR by a virulent pathogen infection.