Ovipositional deterrent in the sweet pepper, Capsicum annuum, at the mature stage against Liriomyza trifolii (Burgess)

Liriomyza trifolii (Burgess), the American serpentine leafminer fly, is well known as a serious pest throughout the world. This insect attack over 21 different plant families including solanaceae plants. The mature sweet pepper, Capsicum annuum (Solanaceae), however, shows resistance to this leafminer fly. This resistance is based on the ovipositional deterrent in the sweet pepper leaf against the fly species. Based on bioassay-guided fractionation, luteolin 7-O-beta-D-apiofuranosyl-(1-->2)-beta-D-glucopyranoside was isolated and identified as the ovipositional deterrent against this insect species. This compound completely deterred L. trifolii females from laying their eggs on a host plant leaf treated at 4.90 microg/cm2.     

Induction of resistance against the leafminer, Liriomyza trifolii, by jasmonic acid in sweet pepper

Sweet pepper (Capsicum annuum) leaves at the mature stage have strong ovipositional deterrence against Liriomyza trifolii (Burgess) (Diptera, Agromyzidae), whereas the cotyledons are fiercely attacked by the fly. Treatment of the cotyledons with 50 microM and 100 microM of a jasmonic acid (JA) solution caused the plant to acquire strong oviposition deterrence against the leafminer. An HPLC analysis of the JA-treated cotyledons revealed the inducible accumulation of a compound. Based on spectroscopic analysis and chemical methods, the induced compound was identified to be caffeoylputrescine (CP). The accumulated amounts of CP in the cotyledons treated with 0, 10, 50 and 100 microM of JA were 6.0, 43.0, 105 and 140 microg/g fr. wt., respectively. Treatment of the cotyledons with CP resulted in a significant decrease in the number of punctures made by L. trifolii, indicating that the JA treatment enhanced the deterrence against the leafminer by inducing CP accumulation.     

Nitrogenous ovipositional deterrents in the leaves of sweet pepper (Capsicum annuum) at the mature stage against the leafminer, Liriomyza trifolii (Burgess)

Mature leaves of the sweet pepper, Capsicum annuum, exhibited resistance against the American serpentine leafminer, Liriomyza trifolii (Burgess), Agromyzidae. Based on bioassay-guided fractionation, three compounds, namely 4-aminobutanoic acid, (2S,4R)-4-hydroxy-1-methyl-2-pyrrolidine carboxylic acid and 4-amino-1-beta-D-ribofuranosyl-2(1H)-pyrimidinone, were isolated from the leaves of sweet pepper. These compounds had significant oviposition deterrence towards adult flies of L. trifolii from laying their eggs on host plant leaves treated at 3.70, 16.60 and 6.45 microg/cm(2), respectively.     

Cucurbitane triterpenoid oviposition deterrent from Momordica charantia to the leafminer, Liriomyza trifolii

Females of Liriomyza trifolii, a polyphagous leafminer, are often deterred from ovipositing on Momordica charantia leaves. The methanol extract of M. charantia leaves showed strong oviposition deterrent activity against L. trifolii females on the host plant leaf when it was dipped in the methanol extract at a concentration of 1 g of fresh leaf equivalent/ml. Bioguided fractionation of the methanol extract of the leaves of M. charantia led to the isolation of a new cucurbitane triterpenoid, 7,23-dihydroxy-3-O-malonylcucurbita-5,24-dien-19-al, along with another known compound, momordicine I. Both 7,23-dihydroxy-3-O-malonylcucurbita-5,24-dien-19-al and momordicine I respectively had significant ovipositing deterrent effect towards the adult females of L. trifolii on host plant leaves treated at concentrations of 3.25 and 33.60 microg/cm2.     

Domatia reduce larval cannibalism in predatory mites

Abstract.  1. Acarodomatia are small structures on the underside of leaves of many plant species, which are mainly inhabited by carnivorous and fungivorous mites.
2. Domatia are thought to protect these mites against adverse environmental conditions and against predation. They are considered as an indirect plant defence; they provide shelter to predators and fungivores and these in turn protect the plants against herbivores and fungi.
3. We studied the possible role of domatia of coffee ( Coffea arabica L.) (Rubiaceae) and sweet pepper ( Capsicum annum L.) (Solanaceae) in reducing cannibalism in the mites inhabiting the domatia. We measured cannibalism of larvae by adults of the predatory mites Iphiseiodes zuluagai Denmark & Muma and Amblyseius herbicolus Chant on coffee leaf discs and of the predatory mite Iphiseius degenerans (Berl.) on sweet pepper leaf. Domatia were closed with glue or left open.
4. Cannibalism in all three species increased when domatia were closed. With I. degenerans , moreover, we found that the previous diet of the cannibal attenuated the effect of domatia on cannibalism.
5. We conclude that domatia can protect young predatory mites against cannibalism by adults and that the diet of cannibals affects the rate of cannibalism.     

过量表达辣椒CaNPR1提高烟草对青枯菌的抗性

对水稻和拟南芥等模式植物的研究表明,NPR1(nonexpressor of pathogenesis-related genes 1)是依赖于SA通路的防御反应调节基因,但在辣椒和烟草等茄科作物中该蛋白的功能还鲜有报道.研究从辣椒cDNA文库中分离获得一个NPR1的类似物全长cDNA(CaNPR1),并获得了其超表达的转基因烟草T1代株系.研究结果表明,这些株系与其野生型植株没有明显表型差异,但却表现出较野生型植株更高的抗青枯菌侵染活性.同时,研究还发现CaNPR1的超表达还显著提高了防御相关基因的表达,表明NPR1在不同植物间具有较强的功能保守性.     

Differences among plant species in acceptance by the spider mite Tetranychus urticae Koch

Abstract:  The spider mite Tetranychus urticae Koch has a broad range of host plants. However, the spider mite does not accept all plants to the same degree because of differences in nutritive and toxic constituents. Other factors, such as the induction of secondary metabolites, the morphology of a leaf surface and the presence of natural enemies, also play an important role in plant acceptance. We compared plants from various families in their degree of acceptance by the spider mite, to get an indication of the plant's direct defence. Glycine max (soybean), Humulus lupulus (hop), Laburnum anagyroides (golden chain) and Nicotiana tabacum (tobacco) were highly accepted by the spider mites. Different glandular hair densities among tobacco cultivars did not affect their suitability towards spider mites significantly. Solanum melalonga (eggplant), Robinia pseudo-acacia (black locust), Vigna unguiculata (cowpea) and Datura stramonium (thorn apple) were accepted by the spider mites to a lesser degree. Vitis vinifera (grapevine) was poorly accepted by the spider mite. It might be that the food quality of the leaves was not high enough to arrest the spider mites. Also, Capsicum annuum (sweet pepper) and especially Ginkgo biloba (ginkgo) were poorly accepted by the spider mite, probably because of the presence and concentration of certain of the secondary metabolites in the leaves. The spider mites accepted all the plants belonging to the Fabaceae for feeding, but those belonging to the Solanaceae showed a larger variance in spider mite acceptance varying from well accepted (tobacco) to poorly accepted (sweet pepper).     

Inheritance of resistance to Meloidogyne incognita race 2 in the hot pepper cultivar Carolina Cayenne (Capsicum annuum L.)

Root-knot nematodes of the genus Meloidogyne are important pathogens affecting vegetable crop production in Brazil and worldwide. The pepper species Capsicum annuum includes both hot and sweet peppers; very little emphasis has been placed on breeding sweet peppers for nematode resistance. We report on the inheritance of resistance to Meloidogyne incognita (Kofoid & White) Chitwood race 2 in the hot pepper cultivar Carolina Cayenne. The hot pepper cv. Carolina Cayenne was used as seed parent and the sweet pepper cv. Agron?mico-8 was used as pollen parent to obtain the F(1) and F(2) generations and the backcross generations BC(11) and BC(12). The plants were inoculated with M. incognita race 2 at a rate of 60 eggs/ml of substrate and, after a suitable incubation period, the numbers of root galls and egg masses per root system were evaluated on each plant. Broad- (0.77 and 0.72) and narrow-sense (0.77 and 0.63) heritability estimates were high for both root galls and egg masses, respectively. The mean degree of dominance was estimated as 0.29 and 0.25 for numbers of galls and egg masses, respectively; these estimates were not significantly different from 0, indicating a predominantly additive gene action. The results were consistent with a hypothesis of monogenic resistance in Carolina Cayenne.     

Cucurbitane glucosides from Momordica charantia leaves as oviposition deterrents to the leafminer, Liriomyza trifolii

The American serpentine leaf mining fly, Liriomyza trifolii, whose larva feeds on more than 120 plant species is well characterized by its high degree of polyphagy. Observations on the oviposition behavior by L. trifolii demonstrated that among cucurbitaceous plants, Momordica charantia is rarely attacked by L. trifolii. The methanol extract of M. charantia leaves strongly deterred the females from ovipositing on kidney bean leaves treated at a concentration of 1 g leaf equivalent extract/ml. Analysis of the polar fraction of the methanol extract of M. charantia leaves resulted in the isolation of a novel cucurbitane glucoside, 7-O-beta-D-glucopyranosyl-3,23-dihydroxycucurbita-5,24-dien-19-al, named momordicine IV, along with another known compound, momordicine II. Momordicine II and IV deterred oviposition by L. trifolii significantly when bioassays were carried out on kidney bean leaves treated at 75.6 and 20.3 microg/cm2 leaf surface, respectively. There was no synergistic effect on oviposition deterrent when the two compounds were combined in their natural abundance.     

Cellulase applied to the leaves of sweet pepper (Capsicum annuum L. var. grossum) upregulates the production of salicylic and azelaic acids

Treating the leaves of sweet pepper (Capsicum annuum L. var. grossum) with an aqueous solution of cellulase resulted in a four-fold increase in the salicylic acid level compared to a control plant. The level of endogenous azelaic acid was also elevated by the cellulase treatment. Azelaic acid has recently been reported to act as a mobile "priming" agent to arm plants against pathogenic attack. Our results are consistent with this and that the cellulase treatment enhanced the ability of sweet pepper to withstand viral attack.     

Host-plant species modifies the diet of an omnivore feeding on three trophic levels

The diet choice of omnivores feeding on two adjacent trophic levels (either plants and herbivores or herbivores and predators) has been studied extensively. However, omnivores usually feed on more than two trophic levels, and this diet choice and its consequences for population dynamics have hardly been studied. We report how host-plant quality affects the diet choice of western flower thrips feeding on three trophic levels: plants (cucumber or sweet pepper), eggs of spider mites and eggs of a predatory mite that attacks spider mites. Spider mites feed on the same host plants as thrips and produce a web that hampers predator mobility. To assess the indirect effects of spider mites on predation by thrips, the thrips were offered spider-mite eggs and predatory-mite eggs on cucumber or sweet pepper leaf discs that were either clean, damaged by spider mites but without spider-mite web, or damaged and webbed. We show that, overall, thrips consumed more eggs on sweet pepper, a plant of low quality, than on cucumber, a high quality host plant. On damaged and webbed leaf discs (mimicking the natural situation), thrips killed more predator eggs than spider-mite eggs on sweet pepper, but they killed equal numbers of eggs of each species on cucumber. This is because web hampered predation on spider-mite eggs by thrips on sweet pepper, but not on cucumber, whereas it did not affect predation on predatory-mite eggs. We used the data obtained to parameterize a model of the local dynamics of this system. The model predicts that total predation by the omnivore has little effects on population dynamics, whereas differential attack of predator eggs and spider-mite eggs by the omnivore has large effects on the dynamics of both mite species on the two host plants.     

Factors affecting oviposition of Bemisia tabaci (Genn.) biotype B in sweet pepper

Bemisia tabaci (Gen.) biotype B is considered a pest of economical importance for several vegetables. The oviposition behaviour of the whilefly was evaluated in sweet pepper plants. The trials were carried out under greenhouse condition and in the Laboratory of Entomology of DEFERS/UNESP, Campus of Ilha Solteira-SP, with the sweet pepper Magali-R genotype. The effect of plant age on the whitefly oviposition was evaluated in free-choice tests, in plants, 25, 30, 35, 40 and 45-day-old, as egg distribution in the plant and on the leaf blade was evaluated in 35-days-old plants. In a no-choice tests, 35-day-old plants were used to evaluate the effect of the densities of 50, 100, 150, 200 and 250 adults per plant on the number of eggs laid by insects. The silverleaf whitefly preferred to oviposit on the third to sixth leaflets, of the medium and superior part of plants of sweet pepper; the leaf blade areas, located in the lobes right and left close the base of the leaf were the preferential site for whitefly oviposition. Older plants, 40- and 45-day-old, were preferentially used for oviposition, and 200 and 250 adults per plant were both enough to lay a number of eggs that allowed to differentiate among sweet pepper genotypes with different whitefly resistance levels.     

脱落酸对甜椒幼苗抗寒性的诱导效应及其机理研究

以砂培甜椒幼苗为材料,先用不同浓度脱落酸(ABA)进行灌根处理,再分两组分别于常温(25℃～30℃)生长7 d(常温苗)或低温驯化(10℃～15℃)30 d(驯化苗)之后进行低温胁迫(5℃)处理,分析幼苗的生长状况及其细胞质膜伤害、渗透调节物质、活性氧清除系统、内源激素的变化特征,以探讨脱落酸对甜椒抗寒性的诱导效应及机理.结果显示,(1)各浓度ABA对甜椒常温苗和驯化苗的株高、茎重均无显著影响,但显著促进驯化苗的侧根生长,在低温胁迫下,显著降低驯化苗叶片的呼吸速率;(2)常温苗的相对电导率仅在10 mg/L ABA处理中比对照显著降低,而驯化苗在各处理浓度下均显著降低,MDA含量表现出与此类似的变化;(3)叶片脯氨酸、可溶性糖、可溶性蛋白、钾离子等渗透调节物质含量在各浓度ABA处理常温苗和驯化苗中均有所增加,但仅脯氨酸含量的增加达到显著水平.(4)各浓度ABA处理都一定程度上提高了常温苗的SOD活性,显著降低了常温苗的CAT和POD活性,H2O2积累量均显著降低,但对于驯化苗,1.0 mg/L和10 mg/L ABA处理却显著降低其SOD活性,POD和CAT活性无显著差异,H2O2积累量也无显著变化.(5)茎尖的ZR、JA-Me含量及IAA/ZR、均与对照无显著差异,但IAA、ABA含量、ABA/ZR比值明显提高,其中1.0和10 mg/L处理的内源ABA含量以及10 mg/L处理的ABA/ZR比值显著高于对照.研究表明,脱落酸能通过降低甜椒幼苗呼吸速率,提高叶片脯氨酸、可溶性糖、钾离子等渗透调节物质以及ABA的积累来诱导增强甜椒幼苗的抗寒性,减少活性氧自由基的产生和累积量,从而减轻低温胁迫造成的伤害,且低温驯化条件下比常温下效果更加明显.     

Expression of sweet pepper Hrap gene in banana enhances resistance to Xanthomonas campestris pv. musacearum

Banana Xanthomonas wilt (BXW), caused by the bacterium Xanthomonas campestris pv. musacearum, is the most devastating disease of banana in the Great Lakes region of Africa. The pathogen's rapid spread has threatened the livelihood of millions of Africans who rely on banana fruit for food security and income. The disease is very destructive, infecting all banana varieties, including both East African Highland bananas and exotic types of banana. In the absence of natural host plant resistance among banana cultivars, the constitutive expression of the hypersensitivity response-assisting protein (Hrap) gene from sweet pepper (Capsicum annuum) was evaluated for its ability to confer resistance to BXW. Transgenic lines expressing the Hrap gene under the regulation of the constitutive CaMV35S promoter were generated using embryogenic cell suspensions of two banana cultivars: 'Sukali Ndiizi' and 'Mpologoma'. These lines were characterized by molecular analysis, and were challenged with Xanthomonas campestris pv. musacearum to analyse the efficacy of the Hrap gene against BXW. The majority of transgenic lines (six of eight) expressing Hrap did not show any symptoms of infection after artificial inoculation of potted plants in the screenhouse, whereas control nontransgenic plants showed severe symptoms resulting in complete wilting. This study demonstrates that the constitutive expression of the sweet pepper Hrap gene in banana results in enhanced resistance to BXW. We describe the development of transgenic banana varieties resistant to BXW, which will boost the arsenal available to fight this epidemic disease and save livelihoods in the Great Lakes region of East and Central Africa.