Presence Of Glandular Trichomes Research Articles

A Comprehensive Review: Pharmacognostical and Pharmacological Insights into Passiflora foetida

Passiflora foetida, commonly known as "stinking passionflower," is a medicinal plant with a long history of traditional use in various cultures for its therapeutic properties. This review provides an overview of the pharmacognostical and pharmacological characteristics of Passiflora foetida, highlighting its potential as a valuable source of bioactive compounds for pharmaceutical and nutraceutical applications. Pharmacognostical studies of Passiflora foetida encompass its morphological, anatomical, and chemical composition. Macroscopic and microscopic examinations reveal distinctive features such as the presence of glandular trichomes, characteristic floral structures, and specific secondary metabolites including flavonoids, alkaloids, and phenolic compounds. These features aid in the identification and quality control of Passiflora foetida plant material. Pharmacological investigations have demonstrated a wide range of biological activities associated with Passiflora foetida extracts and isolated compounds. These include anti-inflammatory, analgesic, antioxidant, antimicrobial, antidiabetic, and neuropharmacological effects, among others. Mechanistic studies have revealed the involvement of various molecular targets and pathways, supporting its traditional use in managing diverse health conditions. Furthermore, the safety profile of Passiflora foetida has been evaluated, with limited reports of adverse effects at recommended doses. However, further toxicological studies are warranted to fully assess its safety profile and potential interactions with other medications. In conclusion, Passiflora foetida exhibits promising pharmacognostical and pharmacological properties, validating its traditional use as a medicinal plant. Future research should focus on elucidating its mechanisms of action, exploring potential therapeutic applications, and standardizing extraction methods to harness its full therapeutic potential.

From morphology to molecules: A comprehensive study of a novel Derris species (Fabaceae) with a rare flowering habit and reddish leaflet midribs, discovered in Peninsular Thailand.

Derrisrubricosta Boonprajan & Sirich., sp. nov., a new species of the genus Derris Lour. (Fabaceae) was discovered in Peninsular Thailand. The overall morphology demonstrates that the species most resembles D.pubipetala. Nevertheless, the species has several autapomorphies differentiating it from other Derris species, e.g., the presence of reddish midribs of the mature leaflets, sparsely hairy stamen filaments, prominent hairs at the base of the anthers, and presence of glandular trichomes along the leaflet midrib. Additionally, HPLC fingerprints of this species showed a distinction from D.pubipetala by the absence of phytochemical compound peaks after 13 min. Retention Time (RT). Results from molecular phylogenetic analyses also strongly supported the taxonomic status as a new species.

Structural Studies of Mexican Husk Tomato (Physalis ixocarpa) Fruit Cutin.

Green tomato (Physalis ixocarpa) is a specie native to Mexico, and it is known as "tomatillo" or "husk tomato". The fruit contains vitamins, minerals, phenolic compounds, and steroidal lactones, presenting antimicrobial activity and antinarcotic effects. Therefore, it is not only used in traditional Mexican cuisine, but also in traditional medicine to relieve some discomforts such as fever, cough, and amygdalitis. However, it is a perishable fruit whose shelf life is very short. As a part of the peel, cuticle, and epicuticular waxes represent the most important part in plant protection, and the specific composition and structural characterization are significant to know how this protective biopolymer keeps quality characteristics in fresh fruits. P. ixocarpa cutin was obtained by enzymatic treatments (cellulase, hemicellulose, and pectinase) and different concentrations of TFA, and studied through Cross Polarization Magic Angle Spinning Nuclear Magnetic Resonance (CPMAS 13C NMR), Ultra-High Performance Liquid Chromatography coupled to Mass Spectrometry (UHPLC-MS), and was morphologically characterized by Confocal Laser Scanning Microscopy (CLSM) and Scanning Electron Microscopy (SEM). The main constituents identified under the basis of UHPLC-MS analysis were 9,10,18-trihydroxy-octadecanoic acid and 9,10-epoxy-18-hydroxy-octadecanoic acid with 44.7 and 37.5%, respectively. The C16 absence and low occurrence of phenolic compounds, besides the presence of glandular trichomes, which do not allow a continuous layer on the surface of the fruit, could be related to a lower shelf life compared with other common fruits such as tomato (Solanum lycopersicum).

Strawberry genotypes with resistance to Tetranychus urticae mediated by leaf trichomes

ABSTRACT The two-spotted spider mite (Tetranychus urticae) is the main pest encountered in strawberry cultivation in protected environments, causing damage and increasing the cost of production associated with chemical control. Breeding programs are essential for obtaining new cultivars that are more tolerant to two-spotted spider mites. The objective was to evaluate whether the leaf trichomes mediatethe resistance of intraspecific strawberry hybrids to two-spotted spider mites. Preselected hybrids were subjected to infestation by two-spotted spider mites and evaluated via the no-choice assay and the travel test. Resistance was correlated with the density of trichomes, both glandular and non-glandular, present on the surface of the leaflets of strawberry genotypes. The results indicated that there is an influence of hybrids and cultivars on the behavior of the pest, allowing the verification of the existence of resistant genotypes (RVDA#16, RVCS#44 and Camino Real). These treatments resulted in low numbers of eggs deposited and hatched compared with the other treatments and shorter distances traveled by two-spotted spider mites on the surface of leaflets. It was also verified that the glandular trichomes presented a significant negative correlation with the average distance traveled by two-spotted spider mites on the surface of the leaf discs, indicating that these structures alter the behavior of these arthropods. Genotype resistance was associated with the presence of glandular trichomes. In addition to the superiority of the agronomic and postharvest attributes of the preselected hybrids (RVDA#16 and RVCS#44) identified in the previous selection efforts, they proved to be promising materials for achieving resistance to the spider mite, revealing important genotypes for use as cultivars and particularly as parents in breeding programs.

Anatomical characterization, histochemistry and crystal analysis of the leaf blade of Mangifera indica L.

Mangifera indica L., popularly known as mangueira, is an important fruitful widely used in Brazilian traditional medicine for the treatment of diabetes, anemia, diarrhea, hemorrhoids, indigestion, asthma, bronchitis, flu, hypertension, rheumatism, disorders of the liver and for tumors. In order to expand the pharmacobotanical information about the species, this study aimed to perform the anatomical characterization, histochemistry and crystal analysis of the leaf blade of M. indica. For the anatomical characterization were used optical microscopy, polarization microscopy and scanning electron microscopy. Histochemical tests were performed to evidence the presence of metabolites and microchemical analyzes by dispersive energy spectroscopy were done to determine the elemental chemical composition of the crystals. The microscopic analysis allowed the identification of characters useful in the identification of the species, such as the presence of glandular trichomes in the leaf blade. Through histochemistry was evidenced the presence of phenolic compounds, lipophilic substances, lignin and starch in the leaf blade. The chemical nature of the crystals was determined to be calcium oxalate. The results contribute to the pharmacobotanical standardization of M. indica.

Study of the influence of wavelengths and intensities of LEDs on the growth, photosynthetic pigment, and volatile compounds production of Lippia rotundifolia Cham in vitro

Lippia rotundifolia Cham. is in the family Verbenaceae and is endemic to the Cerrado. This species is aromatic and characterized by the presence of glandular trichomes on its leaves that are rich in monoterpenes. The objective of this study was to evaluate the growth, photosynthetic pigment production, and chemical composition of L. rotundifolia grown in vitro under different light wavelengths and intensities. The light intensities consisted of five treatments using cool white fluorescent lamps at 20, 54, 78, 88, and 110 μmol m−2 s−1. The light quality consisted of six treatments using light-emitting diodes (LEDs) in different light wavelengths, namely, white, red, blue, and their interactions: 1R:1B, 2.5R:1B, and 1R:2.5B. After 45 days, the biometric parameters, photosynthetic pigment content, and volatile compounds were evaluated. The lower light intensities of 20 and 54 μmol m−2 s−1 generated higher growth, photosynthetic pigment content, and biomass accumulation. Myrcene and pentadecane were highest under light intensities of 88 and 110 μmol m−2 s−1, respectively. The highest limonene and ocimenone levels were obtained at 20 and 54 μmol m−2 s−1 intensity, respectively, and the highest myrcenone content was obtained at 78 μmol m−2 s−1 intensity. Regarding the light wavelengths, the combination of red and blue spectra further stimulated plantlet growth, and the 2.5R:1B combination obtained the best biometric data and total chlorophyll content. The z-ocimenone chemical compound contents were highest under the 1R:2.5B light spectrum. The monochromatic blue spectrum increased the myrcene and limonene content but decreased the myrcenone content, which was increased by red light. The highest pentadecane contents were obtained with the white spectrum and the red and blue combinations.

Caterpillars Cooperate to Overcome Plant Glandular Trichome Defenses

One common advantage proposed for group-living in animals is social facilitation of feeding, by which food acquisition by an individual is made easier by feeding neighbours. The present paper provides an explanation of social facilitation of feeding in a gregarious leaf-chewing insect, demonstrating how caterpillars cooperate to overwhelm plant trichome defenses and pierce a hole in the leaf on which they feed collectively. Specifically, it tests the hypotheses that the caterpillars feed collectively, that the glandular trichomes of Solanum acerifolium are effective defenses against the specialist caterpillar Mechanitis menapis, and that feeding by early-instar M. menapis is socially facilitated in the presence of glandular trichomes. A field survey showed that Mechanitis menapis on trichome–bearing plants feed collectively on the abaxial surface of leaves during the first larval instars. In a lab experiment comparing feeding on control and ethanol-washed leaves, caterpillars on the glandular-trichome-free washed sides of leaves initiated feeding sooner and had higher survival rates, suggesting that glandular trichomes are effective defenses. Behavioural observations showed that feeding is socially facilitated in response to glandular trichomes: caterpillars on the washed sides of leaves were more likely to begin feeding alone and initiated more separate feeding sites, suggesting that caterpillars are less able to initiate feeding independently in the presence of glandular trichomes. These results demonstrate a novel mechanism of cooperation among folivores, showing how they can benefit from grouping to tackle food sources that would be unavailable to isolated individuals. This study thus demonstrates that social facilitation of feeding extends to insect folivores, a hyper-diverse and abundant feeding guild.

QTL mapping of insect resistance components of Solanum galapagense

Key messageQTLs for insect resistance parameters, trichome type IV development, and more than 200 non-volatile metabolites, including 76 acyl sugars, all co-locate at the end of Chromosome 2 of Solanum galapagense.Host plant resistance is gaining importance as more and more insecticides are being banned due to environmental concerns. In tomato, resistance towards insects is found in wild relatives and has been attributed to the presence of glandular trichomes and their specific phytochemical composition. In this paper, we describe the results from a large-scale QTL mapping of data from whitefly resistance tests, trichome phenotyping and a comprehensive metabolomics analysis in a recombinant inbred line population derived from a cross between the cultivated Solanum lycopersicum and the wild relative S. galapagense, which is resistant to a range of pest insects. One major QTL (Wf-1) was found to govern the resistance against two different whitefly species. This QTL co-localizes with QTLs for the presence of trichomes type IV and V, as well as all 76 acyl sugars detected and about 150 other non-volatile phytochemicals, including methyl esters of the flavonols myricetin and quercetin. Based on these results, we hypothesize that Wf-1 is regulating the formation of glandular trichome type IV on the leaf epidermis, enabling the production and accumulation of bioactive metabolites in this type of trichomes.

Leaf micromorphology, antioxidative activity and a new record of 3-deoxyamphoricarpolide of relict and limestone endemic Amphoricarpos elegans Albov (compositae) from Georgia

We examined for the first time the leaf micromorphology, phytochemistry and biological activity of the rare and stenoendemic Amphoricarpos elegans Albov (Compositae) from Georgia. Scanning electron microscopy (SEM) revealed the presence of glandular trichomes on the leaves, which appeared as glandular dots that are considered the main sites of biosynthesis and accumulation of sesquiterpene lactones. Using high-performance liquid chromatography (HPLC) and nuclear magnetic resonance (NMR) spectroscopy analyses, we identify and characterized 3-deoxyamphoricarpolide, a known sesquiterpene lactone for the genus Amphoricarpos Vis. Regarding chemotaxonomic significance, 3-deoxyamphoricarpolide represents a link between Balkan and Caucasian species of the genus. The antioxidative capacity of different leaf extracts, obtained using a Soxhlet extractor, was evaluated by two radical scavenging assays: DPPH (1,1-diphenyl-2-picrylhydrazyl) radical and the 2,2?-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS), and ferric ion reducing antioxidant power (FRAP). The total phenolic and flavonoid contents were also determined. The highest antioxidative activity and the highest phenolic and flavonoid contents were detected in the methanol fraction, as a result of the contribution of not only phenols, but probably also lactones. The considerable antioxidative potential indicates possible applications in pharmacy and medicine.

THE SECRETORY STRUCTURE OF ESSENTIAL OILS IN SOME SPECIES OF LAMIACEAE FOR TRADITIONAL COSMETICS OF BESEMAH TRIBES LAHAT’S DISTRICT

Besemah tribe uses plants in addition to the treatment is also used for beauty treatments traditionally. Based on Agustina's (2015) study, 109 species of plants were used for traditional medicine by the Tribe of Besemah. Some species of Lamiaceae for traditional medicine such as patchouli (Pogostemon cablin (Blanco) Benth.), wild mint (Mentha arvensis L.), hoary basil (Ocimum americanum L.), mexican mint (Plectranthus amboinicus (Lour.) Spreng.), and sweet basil (Ocimum basilicum L.) contains essential oils that can be used for traditional cosmetic ingredients. Essential oils are stored in the secretory structure of plants in leaf and stem organs. This study aims to determine the type and location of the secretory structure of essential oils in some species of lamiaceae used for traditional cosmetics of Besemah Tribes Lahat’s District. The research was conducted in November 2016 until February 2017. The results showed that patchouli plants was found in the presence of glandular trichomes, oil cells, and idioblast cells. The wild mint plants have glandular trichomes. The hoary basil plants have glandular trichomes and oil cells. The mexican mint plants have glandular trichomes and idioblast cells. The sweet basil plants have glandulartrichomes.Keywords: essential oils, lamiaceae, traditional cosmetics, Besemah tribes, glandular trichomes, oil cells, idioblast cells

Aphid resistance in potato

The problem of aphid resistance of potato genetic resources is discussed. Generally, resistance to the green peach aphid (Myzus persicae Sulzer) and the potato aphid (Macrosiphum euphorbiae Thomas) is analyzed in all available literature sources. The Solanum tuberosum L. gene pool contains very few resistant forms. Accessions highly resistant to M. persicae were revealed among 36 of 86 examined wild potato species. The largest number of resistant forms was found among S. bulbocastanum Dun., S. tarijense Hawkes, S. infundibuliforme Phil., S. canasense Hawkes and S. stoloniferum Schlechtd. et Bche. The forms highly resistant to M. euphorbiae belong to 24 of 85 studied species, namely to 10 of 18 series; the species S. bulbocastanum, S. stoloniferum and S. demissum Lindl. include the maximum number of resistant forms. Wild species accessions with specific and group resistance to aphids were revealed. Glandular pubescence of leaves and stems in such species as S. polyadenium Greenm., S. tarijense and S. berthaultii Hawkes is considered as the main mechanism of resistance. Hybrids between S. tuberosum and S. berthaultii were widely used in breeding programs; however, the presence of glandular trichomes was linked to a number of undesirable characters. It is expected that association between the trichome conditioned insect resistance of S. berthaultii and undesirable agronomic traits could be overcome with the use of molecular genetic methods. Studies of the antifeedant activity of potato glycoalkaloids and their aglucons produced controversial results. In numerous works the aphid resistance of potato is connected with plant physiological state. Differences among wild potato accessions in the localization of resistance factors (leaf surface, epidermis, mesophyll, floema) were found that were indicative of differences of resistance mechanisms in the studied forms. Works on investigating induced aphid resistance in potato have great theoretical and practical significance.

English

Fresh leaves of twelve accessions of Sesamum indicum were collected after 12 weeks of planting and morphological-histology of trichomes were studied. These features may be used for the delimitation and determination of pharmaceutical potentials of the accessions. These accessions were found to exhibit high degree of heterogeneity in their trichome features. Nine types of trichomes were observed: unicellular, glandular peltate, capitate glandular, long unbranched uniseriate, short unbranched uniseriate, scale, multicellular, multiseriate capitate glandular and branched uniseriate trichomes. Lale-duk recorded the highest number (six types), four in accessions Ex-Sudan, Adaw-ting (Improved) and Ex-Gombe 1, three in accessions Ex-Gombe 3, Ex-Gombe 4, Ex-Gombe 5 and Ex-Gombe 6, two in kenana 4, Adaw-wula and Adaw-ting. The most frequent trichome type is short-unbranched uniseriate (76.52%), followed by long-unbranched uniseriate (72.73% and scale (65.11%). The least frequent was multiseriate capitate glandular (11.5%). The density of trichomes varied from accession to accession. Trichome density was the highest in Ex-Gombe 3 (63.2±0.49 mm2) and the lowest was recorded by Ex-Gombe 4 (4.40±0.29 mm2). The high variation in density coupled with the presence of glandular trichomes suggest that all the parts of these accessions probably contain or secrete chemicals that have many uses in the pesticide, pharmaceutical and flavour/fragrance industries and to conserve water. Furthermore, the trichome features varied from accession to accession; hence, are found to be good diagnostic and additional tool in identification as well as nomenclature of the accessions of S. indicum. Key words: Trichomes, identification, pharmaceutical industries, sesame.

A taxonomic review of Scrophularia kakudensis Franch. and its relatives

The morphological characters of Scrophularia kakudensis Franch. and its relatives were examined. The major features of S. kakudensis were determined to resolve the taxonomic confusion with the closely related taxa of S. kakudensis var. microphylla, S. pilosa and S. cephalantha. S. kakudensis is characterized by its flowering in Jul. to Sep., the node numbers on a stem, the size of the leaves, the development of inflorescences and the presence of glandular trichomes on its stems and leaves. S. cephalantha is distinct from S. kakudensis by the earlier flowering season, fewer node numbers on a stem, and fewer numbers of flowers on shorter rachis. Smaller sizes of S. kakudensis var. microphylla, considered to be a problematic character previously, are stable and distinctive from other taxa in the natural habitats of the multiple populations investigated in the study. Therefore, the taxon should remain as a variety of S. kakudensis. An examination of the diagnostic characteristics of S. pilosa, such as its inflorescence type and the presence of a stem with pubescence, does not provide sufficient distinction from S. kakudensis. A type specimen and habitat survey also support the merging of the two taxa. S. pilosa should be treated as a synonym of S. kakudensis, because it is considered to be a misidentification of S. kakudensis.

Chemical Differences in Volatiles between Melittis melissophyllum L. subsp. melissophyllum and subsp. albida (Guss) P. W. Ball (Lamiaceae) Determined by Solid‐Phase Microextraction (SPME) Coupled with GC/FID and GC/MS

Melittis melissophyllum (Lamiaceae) is a perennial herb, typical of woody places, occurring in Italy with two subspecies, i.e., melissophyllum and albida. So far, the classification of these two taxa was only based on morphology, i.e., the presence of glandular trichomes, the dimension of the leaves, and the number of teeth on each side as the main discriminant characters. To find marker compounds to chemically discriminate the subsp. melissophyllum with respect to the subsp. albida, a solid-phase microextraction SPME analysis coupled with GC/FID (=flame ionization detector) and GC/MS was carried out. SPME proved to be a chemotaxonomically useful technique that permitted a clearly differentiation of the two subspecies at headspace level. The subsp. melissophyllum was characterized by high amount of the mushroom alcohol oct-1-en-3-ol and the phenolic coumarin, whilst the subsp. albida exhibited a high content in monoterpenes and sesquiterpenes, α-pinene, sabinene, and (E)-caryophyllene being the major compounds. Multivariate chemometric techniques, such as cluster analysis (CA) and principal-component analysis (PCA), were used to support chemical data and characterize the population according to the taxonomy. In addition, the micromorphology and distribution of glandular trichomes of both subspecies were studied by scanning electron microscopy (SEM).

The foliar micromorphology of Arctotis arctotoides (L.f.) O. Hoffm

The foliar micromorphology of Arctotis arctotoides (L.f.) O. Hoffm. a medicinal plant in the Eastern Cape Province, South Africa was investigated using the Scanning Electron Microscope (SEM). The leaf surfaces of the plant were characterized by anisocytic stomata, glandular and non-glandular trichomes. The abaxial surfaces had more stomata and glandular trichomes than the adaxial surfaces of the leaf. Crystal deposits were also observed around the stomata and near the glandular trichomes. Energy dispersive X-ray spectroscopy showed that Na, Mg and Ca were the major constituents of the crystals. Naturally, distinct morphological variations existed among the ultra structures on the leaf surfaces of the plant. The distributions of the stomata and the two types of trichomes on both surfaces also differed both in shape and in structure. The presence of glandular trichomes on the leaf surfaces of this herb may serve as secretory sites where secondary metabolites are produced. Key words: Arctotis arctotoides, foliar micromorphology, stomata, trichomes, crystals.

Microhabitat use by Peucetia flava (Oxyopidae) on the glandular plant Rhyncanthera dichotoma (Melastomataceae)

Several studies have reported that plant structural components can exert strong influences on the density and distribution of spiders. However, little is known about which plant traits mediate specific associations between spiders and plants. In southeastern Brazil, the lynx spider Peucetia flava Keyserling 1877 (Oxyopidae) is commonly found on the plant Rhyncanthera dichotoma (Melastomataceae), a shrub that bears glandular trichomes. In this study we investigated if Peucetia occurs strictly on Rhyncanthera and what plant parameters influence the spiders' distribution. In addition, we recorded the vertical distribution of spiders of different ages in the plant canopy. Throughout the year Peucetia was observed only on the glandular plant Rhyncanthera, indicating that this association is specific and predictable. Statistical analysis showed no difference in the number of spiders between plants of Rhyncanthera with and without flowers, suggesting that this specific association is mediated by the presence of glandular trichomes, and not by reproductive structures. The distribution of Peucetia over the year was related to the number of arthropods on plants, as well as the number of leaves and height of the host plants, indicating that Peucetia probably choose sites of high food availability. Adults and subadults occurred on higher places on the crown than young and juveniles.

The Molecular Cloning of Artemisinic Aldehyde Δ11(13) Reductase and Its Role in Glandular Trichome-dependent Biosynthesis of Artemisinin in Artemisia annua

At some point during biosynthesis of the antimalarial artemisinin in glandular trichomes of Artemisia annua, the Delta11(13) double bond originating in amorpha-4,11-diene is reduced. This is thought to occur in artemisinic aldehyde, but other intermediates have been suggested. In an effort to understand double bond reduction in artemisinin biosynthesis, extracts of A. annua flower buds were investigated and found to contain artemisinic aldehyde Delta11(13) double bond reductase activity. Through a combination of partial protein purification, mass spectrometry, and expressed sequence tag analysis, a cDNA clone corresponding to the enzyme was isolated. The corresponding gene Dbr2, encoding a member of the enoate reductase family with similarity to plant 12-oxophytodienoate reductases, was found to be highly expressed in glandular trichomes. Recombinant Dbr2 was subsequently characterized and shown to be relatively specific for artemisinic aldehyde and to have some activity on small alpha,beta-unsaturated carbonyl compounds. Expression in yeast of Dbr2 and genes encoding four other enzymes in the artemisinin pathway resulted in the accumulation of dihydroartemsinic acid. The relevance of Dbr2 to trichome-specific artemisinin biosynthesis is discussed.

The foliar micromorphology of Solanum pseudocapsicum

Foliar micromorphology of Solanum pseudocapsicum was investigated by electron microscopical examination. The leaves are characterized by anisocytic stomata which are more abundant on the abaxial surfaces. The leaves have short multicellular glandular trichomes sparsely distributed over the entire leaf surfaces. Crystal deposits were also observed on the surfaces above the stomata. Energy dispersive X-ray spectroscopy-SEM showed that Al, K, Na and Si were the major constituents of the crystals analyzed. The presence of glandular trichomes in this plant could be the source of poisonous compounds that are characteristic of this species.

Lipophilic exudates of Pteridaceae - chemistry and chemotaxonomy.

A number of fern species, belonging to several genera of Pteridaceae, exhibit a more or less conspicuous farinose wax, which is mostly located on the lower leaf surface. Production of these waxes is often correlated with the presence of glandular trichomes. Particularly during the past two decades, a series of publications appeared on the chemical composition of these exudates. The major components were found to be flavonoids (chalcones, dihydrochalcones, flavanones, dihydroflavonols, flavones, flavonols), some of them with a complex substitution pattern, including esters and C-methyl derivatives, and even bisflavonoids. Diterpenoids and triterpenoids can also occur in such exudates. It is the purpose of this paper to survey the chemical composition of Pteridaceae exudates and their occurrence within the genera of the family. The chemotaxonomic significance of the flavonoid aglycones at the generic, specific and populational level is briefly discussed.

Variation in tomato host response to Bemisia tabaci (Hemiptera: Aleyrodidae) in relation to acyl sugar content and presence of the nematode and potato aphid resistance gene Mi.

Two commercial cultivars of tomato, Alta and Peto 95, the accession line number LA716 of Lycopersicon pennellii and lines 94GH-006 and 94GH-033 (backcrosses between Peto 95 and LA716), with different leaf acyl sugar contents were screened for resistance to Bemisia argentifolii Bellows & Perring (corresponding to the Spanish B-biotype of Bemisia tabaci (Gennadius)), in greenhouse- and field-no-choice experiments. There was no oviposition on LA716 (with the highest acyl sugar content) while the greatest fecundity and fertility values were observed on the cultivar Alta (no acyl sugar content). However, no clear relationship was found between the low acyl sugar content in the other tomato cultivars tested and whitefly reproduction. Thus, resistance to B. tabaci did not appear to correlate with acyl sugar content below a threshold level of 37.8 microg cm-2 leaf. In a greenhouse choice-assay, B. tabaci exhibited reduced host preference and reproduction on the commercial tomato cultivars Motelle, VFN8 and Ronita all of which carry the Mi gene resistance to Meloidogyne nematodes and the aphid Macrosiphum euphorbiae (Thomas), than on the Mi-lacking cultivars Moneymaker, Rio Fuego and Roma. When data of Mi-bearing plants were pooled, the mean values for daily infestation and pupal production of B. tabaci were significantly lower than those of Mi-lacking plants. This reflected a level of antixenosis- and antibiosis-based resistance in commercial tomato and indicated that Mi, or another closely linked gene, might be implicated in a partial resistance which was not associated either with the presence of glandular trichomes or their exudates. These findings support the general hypothesis for the existence of similarities among the resistance mechanisms to whiteflies, aphids and nematodes in commercial tomato plants.