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.     

Ovipositional deterrent on mature stage of sweet pepper, Capsicum annuum, against Liriomyza trifolii (Burgess)

Liriomyza trifolii (Burgess), the American serpentine leafminer fly, is a well-known serious pest in the world. This insect species attacks plants of more than 21 families including Solanaceae plants. A sweet pepper, Capsicum annuum (Solanaceae), on mature stage, 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 the bioassay guided fractionation, phytol [(2E)-3,7,11,15-tetramethyl-2-hexadecen-1-ol] was isolated and identified as an ovipositional deterrent against this insect species. The yield of this compound was 815 microg/g fresh leaf of C. annuum. This compound completely deterred the females from laying their eggs on host plant leaves treated at 35.2 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.     

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.     

Biocontrol agents against the leafminer,Liriomyza trifolii in faba bean fields

Effect of entomopathogenic fungi formulations, Beauveria bassiana, Verticillium lecanii, Metarhizium anisopliae and Paecilomyces fumosoroseus, in controlling Liriomyza trifolii (Burg.) (Diptera: Agromyzidae), compared with botanical insecticide, Nimbecidine against L. trifolii was studied. Investigated compounds were applied twice at 15?days interval between sprays. The percentage reduction in larvae population and crop yield was estimated. Results showed that M. anisopliae was the most efficient compound among the other entomopathogenic fungi. Also, there were no significant differences between Nimbecidine and Bio-Magic (M. anisopliae). However, Nimbecidine and Bio-Magic caused 69.9 and 68.9% reduction in live larvae population after two applications. Also, Nimbecidine and Bio-Magic plots achieved 14.7 and 10.0?kg dry weight seeds/100 plants, respectively, compared to 5.7?kg dry weight seeds/100 plants in control plots. Nimbecidine and Bio-Magic were considered promising compounds in controlling L. trifolii and it could be exploitation in the integrated pest management programme of faba bean crop.     

Light-dark regulation of carotenoid biosynthesis in pepper (Capsicum annuum) leaves

The carotenoid content in photosynthetic plant tissue reflects a steady state value resulting from permanent biosynthesis and concurrent photo-oxidation. The contributions of both reactions were determined in illuminated pepper leaves. The amount of carotenoids provided by biosynthesis were quantified by the accumulation of the colourless carotenoid phytoene in the presence of the inhibitor norflurazon. When applied, substantial amounts of this rather photo-stable intermediate were formed in the light. However, carotenoid biosynthesis was completely stalled in darkness. This switch off in the absence of light is related to the presence of very low messenger levels of the phytoene synthase gene, psy and the phytoene desaturase gene, pds. Other carotenogenic genes, such as zds, ptox and Icy-b also were shown to be down-regulated to some extent. By comparison of the carotenoid concentration before and after transfer of plants to increasing light intensities and accounting for the contribution of biosynthesis, the rate of photo-oxidation was estimated for pepper leaves. It could be demonstrated that light-independent degradation or conversion of carotenoids e.g. to abscisic acid is a minor process.     

Carbohydrate metabolism during fruit development in sweet pepper (Capsicum annuum) plants

Growth, accumulation of sugars and starch, and the activity of enzymes involved in sucrose mobilization were determined throughout the development of sweet pepper fruits. Fruit development was roughly divided into three phases: (1) an initial phase with high relative growth rate and hexose accumulation, (2) a phase with declining growth rate and accumulation of sucrose and starch, and (3) a ripening phase with no further fresh weight increase and with accumulation of hexoses, while sucrose and starch were degraded. Acid and neutral invertase (EC 3.2.1.26) were closely correlated to relative growth rate until ripening and inversly correlated to the accumulation of sucrose. Acid invertase specifically increased during ripening, concurrently with the accumulation of hexoses. Sucrose synthase (EC 2.4.1.13) showed little correlation to fruit development, and in periods of rapid growth the activity of sucrose synthase was low compared to the invertases. However, during late fruit growth sucose synthase was more active than the invertases. We conclude that invertase activities determine the accumulation of assimilates in the very young fruits, and a reactivation of acid invertase is responsible for the accumulation of hexoses during ripening. During late fruit growth, before ripening, sucrose synthase is transiently responsible for the sucrose breakdown in the fruit tissue. Results also indicate that pyrophosphate-dependent phosphofructokinase (EC 2.7.1.90) and its activator fructose-2,6-bisphosphate (Fru2,6bisP) are involved in the regulation of the sink metabolism of the fruit tissue.     

Cytokinins and leaf development in sweet pepper (Capsicum annuum L.)

Stimulation of leaf expansion by an exogenous cytokinin was studied in isolated leaf discs of sweet pepper with emphasis on the assimilate utilization of the tissue. Leaf discs were floated on solutions containing sucrose and plant growth regulators. Benzyladenine (BA) promoted the area expansion rate of the leaf discs. Sucrose at 100 mM resulted in increased area expansion rate compared with 10 mM sucrose. However, the increased sucrose concentration had no influence on the effect of BA. Over a period of 24 h, treatment with BA did not result in any change of sucrose uptake nor of the partitioning of assimilated carbon in the leaf discs. Neither did BA treatment affect the activity of acid invertase (EC 3.2.1.26) or pyrophosphate-dependent phosphofructokinase (EC 2.7.1.90) in the leaf discs. We conclude that the observed promotion of leaf area expansion by exogenous BA is not mediated through the uptake of sucrose or the carbohydrate metabolism of the leaf tissue.Abbreviations BA N⁶-benzyladenine - GA₃ gibberellic acid - PPi-PFK pyrophosphate-dependent phosphofructokinase (EC 2.7.1.90) This study was supported by grants from the Danish Research Counsil (SJVF 13-4148 and 13-4547 to P.U. SJVF 13-4146 and 13-4494 to T.H.N.) and from The Research Center for Plant Biotechnology to P.U.     

Androgenesis induction in microspore culture of sweet pepper (Capsicum annuum L.)

Isolated microspore culture experiments were carried out in sweet pepper (Capsicum annuum L.) F₁ hybrid genotypes. In the first experiment, four culture media (W14, B5, MS and NLN) were compared to test their effectiveness in inducing the formation of microspore-derived structures in two genotypes. The experiments revealed the superiority of B5 medium. In the second experiment, the effects of different ratios of 2,4-dichlorophenoxyacetic acid (2,4-D) (0, 0.1, 0.2 and 0.5 mg l⁻¹) and kinetin (0, 0.2 and 0.5 mg l⁻¹) were also investigated in B5 medium with two genotypes. The effect of growth regulators were investigated on the production of microspore-derived calli and embryo-like structures (ELSs), the ratio of the two and plant regeneration (number of regenerated plantlets) in microspore culture. The histological experiments revealed the differences between the microspore-derived ELSs and calli. The most promising results were obtained on the investigated parameters in the presence of 0.1 mg l⁻¹ 2,4-D and 0.2 mg l⁻¹ kinetin producing the highest number of plantlets in both genotypes tested. In the response of 11 genotypes, the androgenesis induction was successful in each sweet pepper genotypes tested using the best basic medium and growth regulators combination. In case of 11 genotypes, the number of ELSs ranged from 20 to 100/Petri dish (an average of 48.1 ELS/Petri dish), while the number of green plantlets varied from 0 to 8 plantlets/Petri dish (an average of 1.5 plantlets/Petri dish) depending on the genotype. The spontaneous rediploidization rate obtained was 25% in isolated microspore.     

Candidatus Phytoplasma trifolii (16SrVI) infection modifies the polyphenols concentration in pepper (Capsicum annuum) plant tissues

Of late, the presence of Candidatus Phytoplasma trifolii was reported as a serious threat to the pepper crop in Zacatecas, México; therefore, asymptomatic and symptomatic pepper plants were collected from a commercial field among three samplings after the fruit set stage was reached. Total DNA was extracted using the CTAB‐based method and tested for phytoplasma using a nested PCR assay, followed by a BLAST, and restriction fragment length polymorphism (RFLP) analysis of 16S rDNA sequences, which confirmed the presence of phytoplasma group 16SrVI, “Candidatus Phytoplasma trifolii” in the symptomatic plants. As the metabolic pathways of pathogen‐infected plants tend to change, resulting in a biochemical differentiation with the noninfected plants, the polyphenolic compound concentrations were quantified from the vegetative tissues (root, stem, leaves and developed fruit/big bud) and were analysed based on a principal component analysis (PCA). Results revealed that, in general, plants tend to a progressive increase in total phenols, flavonoids, condensed tannins and anthocyanins related to the plants exposure to “Ca. P. trifolii” infection, and PCA demonstrated that almost 90% of the observed variance was explained by the first two components. Hence, the phenolic content of the plants increases as a response of the defence mechanism, which reflects its condition and resistance.     

Development of pepper (Capsicum annuum) seed quality

Changes in seed quality in pepper (Capsicum annuum L.) were monitored during seed development and maturation in two seasons. Seed quality was assessed by a number of different tests, but principally by determining seed storage longevity in laboratory tests and seedling growth in glasshouse tests. Mass maturity (defined as the end of the seed-filling phase) occurred 49–53 days after anthesis (DAA) in 1989 (varying among fruit layers) and 53 DAA in 1990 when seed moisture contents were 51–53%. The onset of both germinability and desiccation tolerance occurred either just before or at mass maturity. Maximum potential longevity (assessed by the value of the seed lot constant K_i) was achieved 63–65 DAA, i.e. not until 10–12 days after mass maturity (DAMM), in both years. Seedling dry weights in the glasshouse growth tests were maximal later still - for seeds harvested 17–21 DAMM in 1989 and 17 DAMM in 1990; the effects on seedling weight arose from differences in times from sowing to emergence (P < 0.005) among different seed harvests, with no significant differences in subsequent relative growth rates (P > 0.25). Seed priming reduced mean germination times for seeds harvested at all stages of development, but had little effect on germination capacity and potential longevity, and did not affect the pattern of changes in potential longevity during seed development and maturation. The results contradict the hypothesis that seed quality is maximal at the end of the seed-filling phase and that viability and vigour begin to decline immediately thereafter.     

Influence of NaCl in the irrigation water on yield and quality of sweet pepper (Capsicum annuum)

Summary A field experiment was designed to determine the salt tolerance of three varieties of sweet pepper for paprika, studying the effects of four increasing levels of sodium chloride in the irrigation water (5, 10, 29 and 42 meq/l) on soil salinity, yields, and quality of the fruits. EC_5:1 and the soluble sodium and chloride contents increased with increasing salinity. The yields were reduced by 5 per cent for variety ‘Ramillete’, 19 per cent for ‘Tres cascos’, and 40 per cent for ‘Bola’ at the highest level. The fruit quality variables studied (colour index and chloride contents) differed with the variety. re]19750925     

Chromoplast differentiation in bell pepper (Capsicum annuum) fruits

We report here a detailed analysis of the proteome adjustments that accompany chromoplast differentiation from chloroplasts during bell pepper (Capsicum annuum) fruit ripening. While the two photosystems are disassembled and their constituents degraded, the cytochrome b₆f complex, the ATPase complex, and Calvin cycle enzymes are maintained at high levels up to fully mature chromoplasts. This is also true for ferredoxin (Fd) and Fd-dependent NADP reductase, suggesting that ferredoxin retains a central role in the chromoplasts’ redox metabolism. There is a significant increase in the amount of enzymes of the typical metabolism of heterotrophic plastids, such as the oxidative pentose phosphate pathway (OPPP) and amino acid and fatty acid biosynthesis. Enzymes of chlorophyll catabolism and carotenoid biosynthesis increase in abundance, supporting the pigment reorganization that goes together with chromoplast differentiation. The majority of plastid encoded proteins decline but constituents of the plastid ribosome and AccD increase in abundance. Furthermore, the amount of plastid terminal oxidase (PTOX) remains unchanged despite a significant increase in phytoene desaturase (PDS) levels, suggesting that the electrons from phytoene desaturation are consumed by another oxidase. This may be a particularity of non-climacteric fruits such as bell pepper that lack a respiratory burst at the onset of fruit ripening.     

三叶斑潜蝇发育起点温度和有效积温的研究

不同恒温条件下测定了三叶斑潜蝇Liriomyza trifolii (Burgess)各虫态的发育历期,并用直线回归法计算出各虫态的发育起点温度和有效积温.结果表明,三叶斑潜蝇的历期、发育速率与温度间相关性明显,其卵、幼虫、蛹及全世代发育起点温度分别为9.20℃、10.80℃、6.43℃、8.40℃,有效积温分别为68...     

Entomopathogenic nematodes for biological control of the leafminer,Liriomyza trifolii (Dipt.: Agromyzidae)

In the laboratory, mortality rates of the agromyzid leafminer larvae,Liriomyza trifolii (Burgess), ranged from 48 to 98% by 20 strains and/or species of steinernematid and heterorhabditid nematodes. In the greenhouse, abamectin provided superior control of larval leafminers, killing 100% of them as compared withSteinernema carpocapsae (Weiser) All strain (24 to 43% leafminer mortality) orS. carpocapsae Liriomyza-selected strain (8 to 44% leafminer mortality); the maximum relative humidity (r.h.) ranged between 81 and 91% and the minimum r.h. between 50 and 70%. In the foghouse under high r.h., the commercially available All strain and the Hawaiian isolate ofS. feltiae (Filipjev) MG-14 strain caused 69 and 67% mean mortality, respectively. There was a significant correlation (P<0.01) between nematode mortality of leafminers and r.h., including the mean, standard deviation, and minimum r.h. during the 48 h after treatment. Average r.h. >92% with a standard deviation of <9% r.h. and a minimum of 72% r.h. providedS. carpocapsae All strain mortality rates of leafminers >65%. The major constraint against the use of nematodes against leafminers in the foliar environment is low r.h. The use of nematodes againstL. trifolii can be successful if the r.h. remains high and if nematodes enter leafmines before desiccation, and the nematodes should be integrated with chemical insecticides such as abamectin to manage pesticide resistance inL. trifolii.     

QTL mapping of fruit-related traits in pepper (Capsicum annuum)

QTL analysis of pepper fruit characters was performed in an F₃ population derived from a cross between two Capsicum annuum genotypes, the bell-type cultivar Maor and the Indian small-fruited line Perennial. RFLP, AFLP^®1, RAPD and morphological markers (a total of 177) were used to construct a comparative pepper-tomato genetic map for this cross, and 14 quantitatively inherited traits were evaluated in 180 F₃ families. A total of 55 QTL were identified by interval analysis using LOD 3.0 as the threshold for QTL detection. QTL for several traits including fruit diameter and weight, pericarp thickness and pedicel diameter were often located in similar chromosomal regions, thus reflecting high genetic correlations among these traits. A major QTL that accounts for more than 60% of the phenotypic variation for fruit shape (ratio of fruit length to fruit diameter) was detected in chromosome 3. This chromosome also contained QTL for most of the traits scored in the population. Markers in linkage groups 2, 3, 8 and 10 were associated with QTL for multiple traits, thereby suggesting their importance as loci that control developmental processes in pepper. Several QTL in pepper appeared to correspond to positions in tomato for loci controlling the same traits, suggesting the hypothesis that these QTL may be orthologous in the two species.     

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.     

Development and karyology of the tapetal layer of anthers in sweet pepper (Capsicum annuum L.)

The tapetal layer of anthers inCapsicum annuum L. is differentiated from the archesporial complex during the early development stage of the anthers. Further development of tapetum proceeds according to the scheme of the cellular polynuclear type. The high rate of polyploidy is characteristic of the whole layer (from 4n to 8n). Cytokinesis does not follow karyokinesis which conditions the inception of two or three-nuclear cells. The majority of the mononuclear cells show the typical plant endomitosis without the chromosome spiralization, accompanied by the structural nuclear change-over. In other cells chromosome spiralization in the prophase and, after passing through the metaphase, restitution of the cell nuclei were observed. The tapetum development has been studied in 12 cultivars of sweet pepper which did not differ in the course of the karyological processes. The subtle differences during the temporal course of degeneration of the whole layer in the postmeiotic period of development were observed.