Lycopersicon Hirsutum Research Articles

Role for Transferrin in Triggering Apoptosis in Helicoverpa armigera Cells Treated with 2-Tridecanone

2-Tridecanone, a plant allelochemical present in a large range of tomato species ( Lycopersicon hirsutum f. glabratum), can induce the expression of Helicoverpa armigera transferrin ( HaTrf), which is necessary for insect growth and development. To gain further insight into the mechanism of HaTrf in response to 2-tridecanone, we measured the iron and H2O2 levels in the hemolymph during exposure to 2-tridecanone and then explored the effect of transferrin downregulation in a H. armigera fat body cell line exposed to 2-tridecanone. We found that the reduction of HaTrf levels via RNA interference caused rapid apoptotic cell death during exposure to 2-tridecanone. There have been no reports about transferrin genes related to apoptosis induced by plant allelochemicals. Our results indicate that HaTrf mediates the inhibition of apoptotic cell death during exposure to 2-tridecanone and provides insight into the importance of transferrin in the interaction between plants and insects.

Exploring Wild Tomato Leaf Extracts in Pesticide Formulations

Crude extracts from the leaves of the wild tomato, Lycopersicon hirsutum f. glabratum accession PI 134417 possess a pestresistance mechanism in their glandular trichomes (plant hairs) and the exudates they produce due to the presence of a mixture of methyl ketones (MKs) that has insecticidal and acaricidal properties. Type IV and VI glandular trichomes on the leaves of PI 134417 grown under greenhouse conditions were counted. Major volatile oils from glandular leaf trichomes were extracted, purified, and quantified using gas chromatography (GC) and mass spectrometry (GC/MS). The main objectives of this investigation were to: 1) monitor seasonal glandular trichomes density on PI 134417 for mass production of MKs and 2) prepare a simplified formulation of MKs for potential use of PI 134417 leaf extracts, which could become a valuable source of natural products, in plant protection against spider mites and cowpea aphids. Type IV and type VI trichomes were greatest (P<0.05) in September and October (97 and 238 trichomes mm-2), respectively. Quantification of MKs in emulsified extracts of PI 134417 revealed the dominance of 2-tridecanone (the 13-carbon methyl ketone) compared to other MKs (2-undecanone, 2-dodecanone, and 2-pentadecanone) on the leaf surface. Crude leaf extracts of PI 134417 prepared in water caused 33 and 22% mortality, whereas, water extracts containing 1% Alkamuls (an organic emulsifier) caused 93 and 82% mortality of spider mites and cowpea aphis, respectively, 1 d after exposure.

Repellency and oviposition deterrence of wild tomato leaf extracts to spider mites, Tetranychus urticae Koch

Glandular trichomes on the leaves of wild tomato, Lycopersicon hirsutum f. hirsutum Mull, also known as Solanum habrochaites (Solanaceae) synthesize and accumulate high levels of methyl ketones (MKs). The potential of using MKs as alternatives to synthetic acaricides for controlling the twospotted spider mite, Tetranychus urticae Koch, is explored in this study. Plants of L. hirsutum accession LA 407 having high concentrations of MKs were grown from seeds under greenhouse conditions. The main objective of this investigation was to conduct bioassays that are quick and easy to implement, consistent over time (repeatable) with the ability to utilize small amounts of test material for testing repellency and fecundity (number of eggs laid by a female mite) of MKs in pure forms and in LA 407 crude extracts. Four MKs (2-tridecanone, 2-undecanone, 2-dodecanone, 2-pentadecanone) and their mixture were screened for their repellency and ability to alter fecundity of spider mites. All MKs repelled spider mites at the two periods tested. Following spraying of tomato leaf extracts prepared in ethanol (ethanol extracts), average number of eggs laid per female mite on bean leaf discs dropped from 0.8 to 0.3 and from 0.9 to 0.3 at 4 and 24 h after exposure representing 65 and 68% reduction, respectively. However, spraying of tomato leaf extracts prepared in water (water extracts) reduced number of eggs laid per female mite from 1.7 to 0.7 and from 2.6 to 0.9 at 4 and 24 h after exposure representing 60 and 67% reduction, respectively. We concluded that all MKs have repellent and egg laying deterrence activities against spider mites. This investigation suggests that ethanol and water extracts of LA 407 have a potential for repelling female spider mites and reducing their laid eggs which might be explored under field conditions for managing populations of spider mites, which could reduce reliance on synthetic acaricides.

Aspectos biológicos de Tuta absoluta (Lepidoptera: Gelechiidae) criada em folhas de diferentes genótipos de tomate

The resistance of tomato genotypes, Lycopersicon esculentum (Miller) (cv. Santa Clara, hybrids: Saladette Italian Ty Tyna, Santa Cruz Debora Ty, Salad Lumi and Saladette Italian Andrea Victory), Lycopersicon hirsutum f. glabratum (C,H, Mull.) (lines PI 134417 and PI 134418) and Lycopersicum pimpinellifolium (Just) (lines NAV 1062 and PI 126931) to Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) was evaluated under laboratory conditions. The line PI 134418 had the most negative effect on T. absoluta in comparison to the control (Santa Clara), lengthening the larval stage and reducing larval and global survival. The line PI 134417 also affected the development of T. absoluta lengthening the larval stage and reducing the larval survival. The other genotypes showed no negative effect on the biology of T. absoluta. We concluded that PI 126931 is susceptible and NAV 1062, Santa Clara, Tyna, Debora, Lumi and Andrea Victory are highly susceptible to T. absoluta, whereas PI 134418 and PI 134417 highlighted with high resistance and moderate resistance, respectively, to T. absoluta of antibiosis-type.

&lt;p&gt;&lt;strong&gt;ROLE OF DIFFERENT TRICHOME STYLE IN THE RESISTANCE OF &lt;em&gt;LYCOPERSICON HIRSUTUM&lt;/em&gt;&lt;/strong&gt; &lt;strong&gt;GENOTYPES TO&lt;em&gt; TUTA ABSOLUTA &lt;/em&gt;(MEYRICK)&lt;em&gt; &lt;/em&gt;(LEPIDOPTERA: GELECHIIDAE)&lt;em&gt; &lt;/em&gt;&lt;/strong&gt;&lt;/p&gt;

The tomato leaf miner (TLM), Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), is one of the major pests that attacks commercial tomato. TLM is becoming resistant to many of the pesticides used in the tomato fields. A potential alternative method of control is host plant resistance, which may be mediated by glandular trichomes. We studied glandular and non-glandular trichomes potentially related to tomato resistance of nine tomato genotypes (Lycopersicon hirsutum Humb &amp; Bonpl), extensively cultivated in western Iran. The antixenosis and/or antibiosis effect of the genotypes Mobil, Falat 3, Cal J N3, Dehghan, Super Strain B, Río Grande, King Ston, Early Urbana and Peto Mech were evaluated under greenhouse conditions (25 ± 1°C, 65 ± 5% R.H., photoperiod of L16: D8 h). TLM elicited the lowest egg-laying response on Peto Mech, Río Grande and King Ston; and the highest one on Dehghan. King Ston and Mobil allowed the lowest and highest larvae density on the leaves, respectively. The highest preference was observed on Mobil and the lowest one on Río Grande and King Ston. Moreover, trichome type and density of the assayed genotypes appeared to be related to TLM population density: the most infested genotype (Mobil and Cal J N3) displayed the lowest IV and VI trichome style ranks of leaf blade, vein and domatia (glandular trichomes). Significant negative relations were found between egg and larvae density with leaf I style trichome; and also larvae and adult density with IV and V style trichome. Finally, this preliminary study screened two genotypes (Río Grande and King Ston) quite promising for developing resistance programs in western Iran against TLM.

The microanalysis on resistance of new tomato genotypes

Microscopic study on the leaf of the new tomato genotypes has shown that the most informative structural indicators of drought resistance of these plants are: a) presence, level of development and the distribution of protective and glandular trichomes on the leaves; b) presence and occurrence of the cells with oxalate calcium sand in the leaf mesophyll. Statistical processing of the results determines that new tomato genotypes 'Line 50' – 'Prizor' × ('Prizor' × Lycopersicon hirsutum) and 'Line 47' – 'FriguAŸor' × (Lycopersicon peruvianum × 'Victoria') are resistant to drought.

Stress responses of tomato protoplasts to copper and paraquat

Plants are often exposed to external biotic or abiotic agents that can damage cells. Biotic agents include molecules produced by pathogens, and abiotic agents include ultraviolet radiation, heavy metals and xenobiotic agents such as herbicides. Because of the importance of abiotic stresses and the limited knowledge of the defense responses of plants to stresses, a study was conducted using flow cytometry to evaluate endocellular events in protoplasts of two tomato species, Lycopersicon hirsutum and Lycopersicon esculentum, following exposure to 10 mM CuCl2 and 1% paraquat. During the first 30 min of exposure to 10 mM CuCl2, mean fluorescence intensity values in both species decreased by more than 50% compared to the untreated control. During the first 30 min of paraquat treatment, the production of reactive oxygen species, evaluated as the incidence of protoplasts in which the superoxide anion was present, was 32.9 % and 25.4%, respectively, for L. hirsutum and L. esculentum. Hyperpolarization of the mitochondria for both tomatoes species was observed during the first 2 h. The absence of early membrane damage and the markedly detrimental effects of the treatments on the mitochondria suggest that additional mechanisms which lead to cell death may be involved in these processes, and that these mechanisms may be associated with apoptosis.

Quantitative trait loci (QTL) analysis for antioxidant and agronomically important traits in tomato (Lycopersicon esculentum)

Tomato is one of the most widely produced and consumed vegetable crops worldwide. Plant breeders have usually focused on improvement of horticulturally important traits such as yield, fruit size, shape and colour. With increased attention on human health, however, plant breeders also consider the improvement of health-related traits of fruits and vegetables such as antioxidant characters. In the present study, genes controlling both health-related and horticulturally important traits were mapped in the tomato genome using 152 Lycopersicon hirsutum BC_2F_2 individuals. For this aim, all plants were phenotypically and genotypically characterised and a total of 75 QTLs were identified for all traits. Of the 75 QTLs, 28 were identified for 5 antioxidant traits including total water soluble antioxidant capacity, vitamin C, total phenolics, total flavonoids, and lycopene contents, and 47 QTLs were identified for 8 agronomic traits including fruit weight, external and internal fruit colour, fruit firmness, fruit shape, stem scar size, locule number, and wall thickness. Markers linked with these QTLs can be used in marker assisted selection (MAS) for improvement of elite tomato lines.

Characterization of Plant-Bacterial Interactions Using Proteomic Approaches

The explosion in the amount of genomic information available has revolutionized almost every aspect of the life sciences including proteomics. In tandem with advances in genomics, considerable developments in proteomic tools and technologies have greatly facilitated the application of proteomics to tackle numerous biological questions. Many measurable characteristics of proteins, including expression levels, cellular distributions, interactions with other molecules, and post-translational modifications, influence and direct their functions in various cellular processes. Proteomic techniques, such as comparative proteomics, mass spectrometry-based identification of post-translational modifications, and protein arrays, can be employed to study these aspects of proteins in a “host plus microbes” setting and in turn shed light on their interactions. This review summarizes the proteomic techniques applicable to host-microbial relations, with a particular focus on plant-bacterial interactions. This article also provides a comprehensive overview of the applications of proteomics in plant-bacterial interactions, including some of the most recent progress in the field. Keywords: Plant, bacteria, pathogen, symbiosis, proteomics, phosphorylation, Arabidopsis thaliana, Oryza sativa, Mycoplasma pneumoniae, two-dimensional electrophoresis, difference in-gel electrophoresis, plant growth-promoting bacteria, Erwinia chrysanthemi, Pectobacterium atrosepticum, isotope-coded affinity tag, Lycopersicon hirsutum, Medicago truncatula, Agrobacterium tumefaciens, Bradyrhizobium japonicum, Methylobacterium extorquens, Drosophila melanogaster, Nostoc punctiforme, Sinorhizobium meliloti, mitogenactivated protein kinases, calciumdependent protein kinases, pathogen-associated molecular pattern, AQUA, absolute quantification, CDPK, calcium-dependent protein kinase, XIC, extracted ion chromatogram, FDR, false discovery rate, PAIs, Protein abundance indices

Resistance to the South American tomato pinworm Tuta absoluta in high acylsugar and/or high zingiberene tomato genotypes

Zingiberene (ZGB) and acylsugars (AS) are allelochemicals responsible for high levels of arthropod resistance found in Solanum habrochaites (= Lycopersicon hirsutum) var. hirsutum ‘PI 127826’ and S. (= L.) pennelli ‘LA 716’, respectively. These accessions were used to develop commercial lines with good levels of pest resistance. The objective of the present work was to assess the ZGB and AS contents and the levels of resistance to Tuta absoluta in tomato hybrids between high ZGB × high AS lines, as compared with their parental lines and with commercial checks. High AS homozygous lines [TOM-688 and TOM-689, both originated from the interspecific cross S. lycopersicum (= L. esculentum) × S. pennelli], high ZGB homozygous lines (ZGB-703 and ZGB-704, both derived from the interspecific cross S. lycopersicum × S. habrochaites var. hirsutum), double heterozygotes for both ZGB and AS, single heterozygotes for ZGB, and single heterozygotes for AS were assessed for AS and ZGB contents. Low-ZGB low-AS checks ‘Debora Max’ and ‘TOM-684’ were used, as well as checks with high ZGB (PI 127826) and high AS (LA 716). The genotypes were submitted to infestation with South American tomato pinworm adults in a screenhouse, and oviposition counts were taken 10 days after the initial infestation date. Plants were scored for overall plant damage and percent leaflets attacked up to the 38th day after infestation. Genotypes heterozygous for ZGB or AS showed allelochemical contents intermediate to those of their high and low content parents, indicating incompletely dominant gene action for contents of each of the allelochemicals. There were no significant differences in T. absoluta oviposition between high-AS homozygous genotypes, high-ZGB homozygotes, single heterozygotes for AS, single heterozygotes for ZGB and double heterozygotes for ZGB and AS, but all these genotypes showed egg counts significantly lower than the low-ZGB low-AS checks. Feeding damage of T. absoluta was higher in the low-ZGB low-AS checks than in any other ZGB-rich or AS-rich tomato genotype. Relative to ZGB or AS single heterozygotes, the heterozygotes for both ZGB and AS showed higher levels of resistance to the insect, as measured by overall plant damage, indicating a synergic effect of the allelochemicals on resistance.

Pattern of genetic variability of Solanum habrochaites in its natural area of distribution

The tomato wild relative species Solanum habrochaites (previously known as Lycopersicon hirsutum) is a potential source of novel genes for tomato breeding. It shows resistance to many diseases and pests, cold tolerance and fruit quality traits. This species inhabits the western Andean slopes at high elevations from central Ecuador to central Peru. In this study the genetic variation of S. habrochaites was studied using 91 accessions from the whole range of distribution of this species. To this end, we employed two kinds of markers: 9 SSRs and 6 AFLP combinations. The Principal Coordinate Analysis based on AFLP data showed the existence of clinal genetic variation from north to south. The accessions of the different geographic groups were sequentially arranged in the first axis from north to south and a clear separation between them was found. The groups from the centre of the area of distribution showed the highest variation and heterozygosis. The ones from the margins showed lower variability and presented higher homozygosis. The morphotypes typicum and glabratum considered by Muller constituted the extreme forms of the continuous variation in the pubescence grade. These differences in pubescence were not associated with the homozygosis grade.

NC 1 CELBR and NC 2 CELBR: Early Blight and Late Blight-resistant Fresh Market Tomato Breeding Lines

NC 1 CELBR and NC 2CELBR are sister lines developed in a long-term breeding program in North Carolina to combine early blight and late blight resistances into adapted fresh-market tomato backgrounds. The pedigree of the two breeding lines traces back to NC 215E-1(93), a large-fruited determinate line with moderate resistance to the foliage blight phase of early blight and high resistance to the stem lesion phase of early blight (Fig. 1). NC 215 E-1(93) has a complex pedigree extending back to NC EBR-1, which has moderate foliage resistance to early blight derived from the Lycopersicon hirsutum L. (currently Solanum habrochaites S. Knapp & D.M. Spooner) source PI 126445 and NC EBR-2, which has moderate foliage resistance and a high level of stem lesion resistance to early blight derived from Campbell 1943 (Gardner, 1988). The Ph-2 gene for late blight resistance was derived from Richter’s wild tomato, and the Ph-3 gene was derived from L. 3707, a selection of the Lycopersicon pimpinellifolium L. (currently Solanum pimpinellifolium L.) line PI 365957 obtained from the Asian Vegetable Research and Development Center (AVRDC). The Ph-2 and Ph-3 genes from these small-fruited sources were backcrossed into NC 215E-1(93) to develop large-fruited lines, which were then crossed to combine the Ph-2 and Ph-3 genes into the early blight resistant background derived from NC 215E-1(93). The resultant F1 hybrid, NC 03220, was selfed, and 96 F2 generation plants were tested in growth chambers using detached leaf inoculations (Brusca, 2003) for combined resistance to isolates (Ph2-OC and Ph3-OC) that specifically overcame Ph-2 and Ph-3. Plants exhibiting a high level of resistance to inoculation with the two isolates (Ph2-OC and Ph3-OC) separately and in combination were selfed in the greenhouse, and F3 generation plants were evaluated in the field for combined resistance to early blight and late blight. Selections were made in the field for the best horticultural traits, including fruit size and smoothness combined with resistances to early blight and late blight. The field selections, 33EB-1(2004) and 45EB2(2004), leading to NC 1 CELBR and NC 2 CELBR, respectively, were derived from a single F2 plant that was homozygous for the Ph-2 and Ph-3 genes combined based on field trials in 2004 and subsequent years and verified by detached leaf inoculations in the growth chamber (Brusca, 2003).

Isolation of Sesquiterpene Synthase Homolog from Panax ginseng C.A. Meyer

Sesquiterpenes are found naturally in plants and insects as defensive agents or pheromones. They are produced in the cytosolic acetate/mevalonate pathway for isoprenoid biosynthesis. The inducible sesquiterpene synthases (STS), which are responsible for the transformation of the precursor farnesyl diphosphate, appear to generate very few olefinic products that are converted to biologically active metabolites. In this study, we isolated the STS gene from Panax ginseng C.A. Meyer, designated PgSTS, and investigated the correlation between its expression and various abiotic stresses using real-time PCR. PgSTS cDNA was observed to be 1,883 nucleotides long with an open reading frame of 1,707 bp, encoding a protein of 568 amino acids. The molecular mass of the mature protein was determined to be 65.5 kDa, with a predicted isoelectric point of 5.98. A GenBank BlastX search revealed the deduced amino acid sequence of PgSTS to be homologous to STS from other plants, with the highest similarity to an STS from Lycopersicon hirsutum (55% identity, 51% similarity). Real-time PCR analysis showed that different abiotic stresses triggered significant induction of PgSTS expression at different time points.

Desenvolvimento de Oidium neolycopersici em genótipos do gênero Lycopersicon

O oídio, causado pelo fungo Oidium neolycopersici, é uma doença comum do tomateiro, sobretudo em condições de cultivo protegido. Para esclarecer a natureza da resistência a oídio avaliou-se o processo de infecção, através da histopatologia em diferentes genótipos de tomateiro: CNPH 416, CNPH 423, CNPH 1287 (Lycopersicon hirsutum), CNPH 0081 (L. esculentum var. cerasiforme), cv. Santa Cruz Kada e cv. Santa Clara (L. esculentum). Para isso, três discos foliares (da 3ª, 4ª e 5ª folha "verdadeira") de cada planta com 5 -7 folhas verdadeiras foram cortados e colocados em placas de Petri contendo ágar-água. Os discos foram inoculados a partir de micélio esporulante fresco desenvolvido em tomateiro suscetível e incubados a 19-22ºC, 4000 lx e fotoperíodo de 12 h. Os discos foram clareados em etanol aquecido e examinados microscopicamente 19 h, 8 e 9 dias após-inoculação para avaliar desenvolvimento de tubo germinativo, esporulação e severidade da doença, respectivamente. A germinação dos conídios sobre o tecido foliar não apresentou diferenças entre genótipos. A formação de hifa secundária, apressórios e haustórios por conídio germinado foram menores nos genótipos CNPH 1287 e 423, que também apresentaram menor esporulação e severidade da doença. Os genótipos de L. esculentum e L. esculentum var. cerasiforme apresentaram maior suscetibilidade ao oídio e CNPH 416 apresentou suscetibilidade intermediária. Assim, observou-se que a resistência a oídio de CNPH 1287 e 423 ficou evidenciada já desde as 19 horas após a inoculação, principalmente pela menor porcentagem de hifa secundária e número de apressórios e haustórios formados quando comparados com os genótipos suscetíveis.

Resistance to Tetranychus evansi in Lycopersicon esculentum L. hirsutum var. glabratum hybrids

SummaryCultivated tomato (Lycopersicon esculentum Mill. cv. Money Maker) was crossed with the spider mite-resistant wild tomato, Lycopersicon hirsutum var. glabratum Mull. accession ‘LA 2204’, and assessed for trichome density and resistance to the spider mite Tetranychus evansi Baker and Pritchard. Trichome types I, III, IV, V, VI, and VII were identified on the abaxial leaf surfaces of the parental genotypes, the inter-specific hybrid, and segregating F2,BC1 and BC2 generations. Type IV trichomes were absent on ‘Money Maker’, while type V were absent on ‘LA 2204’, but the inter-specific hybrid and segregating generations possessed both type IV and type V.Type IV glandular trichomes were predominant on ‘LA 2204’. Type V non-glandular trichomes were predominant on ‘Money Maker’. No T. evansi larvae reached the adult stage on accession ‘LA 2204’; while, on ‘Money Maker’, 52.5% of the larvae reached the adult stage. Mite fecundity and longevity were highest on ‘Money Maker’ (57.9 eggs/female; 13.1 d), and lowest on ‘LA 2204’ (0.04 eggs/female; 4.5 d), and intermediate on the inter-specific hybrid and all segregating generations. In repellence tests, with the thumbtack bioassay, the distance covered by mites on abaxial leaf surfaces was significantly higher on ‘Money Maker’ than on ‘LA 2204’, the inter-specific hybrid, or the segregating generations during the first 20 min. In choice tests, significantly more mites were attracted to ‘Money Maker’ than to the inter-specific hybrid and segregating generations.

Novel Arthropod Repellent, BioUD, Is an Efficacious Alternative to Deet

For >50 yr, N,N-diethyl-3-methylbenzamide (deet) has been the standard for arthropod repellents and has been an important tool to protect people from disease agents carried by ticks, mosquitoes, and other arthropods. However, some people avoid using deet because of concerns about adverse health effects. In 2007, a new repellent, BioUD, with the active ingredient 7.75% 2-undecanone, originally derived from wild tomato (Lycopersicon hirsutum Dunal f. glabratum C. H. Müll) plants, was registered by the U.S. Environmental Protection Agency. In the current study, repellent efficacy of BioUD was compared using arm-in-cage studies with 7 and 15% deet against the mosquitoes Aedes aegypti (L.) and Aedes albopictus Skuse. No differences were found in mean repellency over 6 h after application between BioUD versus 7 and 15% deet for Ae albopictus. For Ae. aegypti, no differences were found over the same time period for 7% deet. Compared with 15% deet, BioUD mean repellency was lower over the 6-h test period. Human subject field trials were conducted in North Carolina, United States, and Ontario, Canada, comparing the repellency of BioUD to products containing 25 and 30% deet. BioUD provided the same repellency or was more efficacious than 25 and 30% deet, respectively, in these studies. Laboratory trials were conducted to determine the repellent activity of BioUD against the American dog tick, Dermacentor variabilis (Say), on human skin and cloth. BioUD repelled ticks at least 2.5 h after application to human skin. On cloth, no differences in mean repellency were found through 8 d after application between BioUD and 7% deet. In a two-choice test for BioUD versus 15% deet on filter paper, ticks spent significantly more time on the deet-treated surface than the BioUD-treated surface. Based on these studies in toto, BioUD is an efficacious alternative to deet in its repellent activity.

Novel Arthropod Repellent, BioUD, Is an Efficacious Alternative to Deet

For >50 yr, N,N-diethyl-3-methylbenzamide (deet) has been the standard for arthropod repellents and has been an important tool to protect people from disease agents carried by ticks, mosquitoes, and other arthropods. However, some people avoid using deet because of concerns about adverse health effects. In 2007, a new repellent, BioUD, with the active ingredient 7.75% 2-undecanone, originally derived from wild tomato (Lycopersicon hirsutum Dunal f. glabratum C. H. Müll) plants, was registered by the U.S. Environmental Protection Agency. In the current study, repellent efficacy of BioUD was compared using arm-in-cage studies with 7 and 15% deet against the mosquitoes Aedes aegypti (L.) and Aedes albopictus Skuse. No differences were found in mean repellency over 6 h after application between BioUD versus 7 and 15% deet for Ae albopictus. For Ae. aegypti, no differences were found over the same time period for 7% deet. Compared with 15% deet, BioUD mean repellency was lower over the 6-h test period. Human subject field trials were conducted in North Carolina, United States, and Ontario, Canada, comparing the repellency of BioUD to products containing 25 and 30% deet. BioUD provided the same repellency or was more efficacious than 25 and 30% deet, respectively, in these studies. Laboratory trials were conducted to determine the repellent activity of BioUD against the American dog tick, Dermacentor variabilis (Say), on human skin and cloth. BioUD repelled ticks at least 2.5 h after application to human skin. On cloth, no differences in mean repellency were found through 8 d after application between BioUD and 7% deet. In a two-choice test for BioUD versus 15% deet on filter paper, ticks spent significantly more time on the deet-treated surface than the BioUD-treated surface. Based on these studies in toto, BioUD is an efficacious alternative to deet in its repellent activity.

Base genética da resistência de um acesso de tomate silvestre ao mosaico-amarelo do pimentão

O objetivo deste trabalho foi avaliar a base genética da resistência de Lycopersicon hirsutum ao potyvírus Pepper yellow mosaic virus (PepYMV). Foram avaliadas 540 plantas, inclusive os parentais 'Santa Clara' (suscetível) e 'BGH 6902' (resistente), e as gerações F1, F2, RC1:1 e RC1:2, derivadas do cruzamento desses parentais. As plantas receberam inoculações mecanicamente, e a concentração viral de PepYMV em cada planta foi determinada por ELISA indireto. Foram realizadas as análises quantitativa e qualitativa. A primeira, baseada na concentração viral de cada planta, indicou herança oligogênica com herdabilidade de 99%. Os mesmos dados, quando analisados de forma qualitativa, indicaram herança governada por dois genes, com interação epistática dominante e recessiva. Entretanto, quando foi analisada a geração F2:3, oriunda da autofecundação de plantas F2 resistentes, a hipótese de dois genes foi descartada e a de um gene, com dominância completa entre os alelos, foi a que melhor se ajustou aos dados. A análise qualitativa, pela sintomatologia observada, demonstrou que a herança da resistência ao PepYMV é determinada por um gene recessivo, com ausência de dominância entre os seus alelos.

Inheritance of resistance to Phytophthora infestans (Peronosporales, Pythiaceae) in a new source of resistance in tomato (Solanum sp. (formerly Lycopersicon sp.), Solanales, Solanaceae)

In Brazil, no commercial tomato (Solanum lycopersicum L. formerly Lycopersicon esculentum Mill.) varieties are available which are resistant to the late blight, one of the most important tomato diseases, produced by the phytopathogenic oomycete Phytophthora infestans. The wild tomato (Solanum habrochaites Knapp & Spooner, formerly Lycopersicon hirsutum Dunal) shows resistance to P. infestans, because of which we investigated an interspecific cross between S. lycopersicum cv. Santa Clara and S. habrochaites accession BGH 6902 maintained at the Horticultural Germplasm Bank at the Federal University of Vicosa (Banco de Germoplasma de Horticultura (BGH), Universidade Federal de Vicosa (UFV), Vicosa, Minas Gerais, Brazil) The genitors, F1, F2, BC1 and BC2 were used to study the inheritance of resistance to P. infestans and to estimate the genetic parameters associated with resistance. Analysis of the area under the disease progress curve (AUDPC) indicated that inheritance is polygenic and that dominance controls character, whereas mean analysis showed that the additive effect was the most important. Although the character presents variability, the heritability is low which generates the need to better control the environment to obtain success with the selection.

Occurrence of 2,3-dihydrofarnesoic acid, a spidermite repellent, in trichome secretions of Lycopersicon esculentum × L. hirsutum hybrids

The sesquiterpenoid spidermite repellent, 2,3-dihydrofarnesoic acid, occurs in trichome secretions of LA1363, an accession of the wild tomato Lycopersicon hirsutum. To better understand the inheritance of this sesquiterpene acid and its relationship with the quantity trichome secretions, interspecific crosses were made with five inbred lines of L. esculentum. Limited seed set and frequent seedling mortality led to small populations for each generation. Concentrations of residues in leaflet washes, comprised of trichome secretions and concentrations of 2,3-dihydrofarnsoic acids were determined in F1, F2 and backcross generations. Low concentrations of this acid occurred in F1 hybrids, suggesting there was dominance for low levels of the acid. However, concentrations of 2,3-dihydrofarnesoic acid were below minimum levels of detection in two backcross generations and in one of two F2 generations. Concentrations of leaflet wash residues were high on the L. hirsutum parent and low on the L. esculentum parents. Concentrations on hybrids were generally intermediate. However, high residue concentrations were present on a few F1 and F2 hybrids, Residue and 2,3-dihydrofarnesoic acid concentrations were not correlated in F1 or in backcross generations and were uncorrelated in one of two F2 generations. In the F2 obtained by sib-mating, residue concentrations were correlated with 2,3-dihydrofarnesoic acid concentrations. Although small population sizes and perhaps other factors did not allow delineation of genetic control of the presence or abundance of 2,3-dihydrofarnesoic acid, interspecific hybrids that produce 2,3-dihydrofarnesoic acid provide the experimental plants essential for research designed to provide a better understanding of the role of 2,3-dihydrofarnesoic acid in host-plant resistance of tomato to mites and insects.