Yield and fruit quality losses caused by ToMV in pepino (Solanum muricatum L.) and search for sources of resistance

Tomato mosaic virus (ToMV) is a limiting factor for the success of pepino (Solarium muricatum) as a new crop. The effects of ToMV infection on total and marketable yield, fruit weight, length/width ratio and soluble solids content (SSC) have been studied in two commercial clones (`Sweet Long' and `Sweet Round'). ToMV infection depressed total yield in infected plants of `Sweet Long' (43.1%), while it had no effect on this trait in `Sweet Round' . Marketable yield was dramatically reduced by ToMV infection in both clones, 94% in `Sweet Long' and 100% in `Sweet Round'. Infected plants of clone `Sweet Long' had a lower weight than healthy plants. Although no differences in fruit weight were detected in `Sweet Round' between ToMV infected and healthy plants, many fruits from infected plants showed deformities. Changes in fruit length/width ratio and SSC as a result of ToMV infection were not relevant, but fruit quality was lower in infected fruits, most of which had corky-like flesh. Forty-two clones from cultivated (S. muricatum), wild (S. caripense and S. tabanoense) and interspecific hybrids were tested for ToMV resistance. All but seven clones (four from S. muricatum and three from interspecific hybrids S. muricatum × S. caripense) were susceptible. Non-susceptible clones showed variable degrees of resistance and developed hypersensitive local lesions. Among these clones the most promising as sources of variation for resistance to ToMV are those belonging to the cultivated species. Although no immunity was found, plants from these clones remained asymptomatic and absorbance values resulting from the DAS-ELISA tests in these plants were always lower than those of the susceptible control (cv. `Sweet Round'). These sources of resistance may be of great utility in developing commercial clones resistant to this severe disease affecting pepino. This revised version was published online in July 2006 with corrections to the Cover Date.     

Wild relatives can contribute to the improvement of fruit quality in pepino (Solanum muricatum)

Narrow intraspecific variation for sugar content in pepino (Solanum muricatum Aiton) hinders the development of new pepino cultivars with improved fruit quality. However, some wild related species have high soluble solids concentration (SSC) and titratable acidity (TA). Generation means analysis was used to estimate genetic parameters for SSC, TA and ascorbic acid concentration (AAC) in two families of interspecific crosses between a S. muricatum parent (Sm-32) and one accession of each of the wild species Solanum caripense (Sc-4) and Solanum tabanoense (St-1). In both families, the additive effect [d] was the only significant parameter for SSC, the alleles of wild species contributing positively to increasing SSC values. For TA, genetic effects associated with additivity [d] and dominance [h] were detected in both families. Additionally, in Sm-32 × Sc-4 nonallelic interactions associated with dominance ([j] and [l]) were significant. For this trait, alleles from the wild species contribute additively to a high value of the character, but are recessive to those of the cultivated S. muricatum. No genetic variation was found for AAC. Broad-sense heritabilities for SSC and TA were intermediate (0.40 to 0.50). Positive significant genetic correlations (around 0.68 in both families) were found between SSC and TA. The results obtained in backcrosses of interspecific hybrids to S. muricatum, together with the estimates of genetic advance after selection, indicate that recovery of individuals with higher SSC and TA and adequate SSC/TA ratio can be achieved in a few backcrosses. In conclusion, this work indicates that wild species S. caripense and S. tabanoense are worthy sources of variation for improving pepino fruit quality. This revised version was published online in July 2006 with corrections to the Cover Date.     

SSR-tagged breeding scheme for allogamous crops: a trial in bunching onion (<Emphasis Type="Italic">Allium fistulosum</Emphasis>)

In several autogamous and vegetatively propagated crops, DNA markers have been used for cultivar identification. However, allogamous crops such as bunching onion (Allium fistulosum L.) are recalcitrant to marker-aided cultivar identification, as well as hybrid seed purity tests, due to the high degree of genetic heterogeneity within each cultivar. To aid cultivar identification and ensure its accuracy in bunching onion, we proposed the “SSR-tagged breeding” scheme in our previous study. The feasibility of this scheme was investigated here using a landrace of bunching onion with two populations tagged with two or four selected SSR markers. Compared with a control population, no significant differences were detected in the agronomic traits of the SSR-tagged populations. The targeted SSR loci were genetically uniform within each population whereas other loci maintained high heterogeneity. These results demonstrate that the SSR-tagged breeding scheme, even with a very small number of markers, is efficient for the identification of newly bred cultivars, and consequently for F₁ purity tests, in allogamous crops in which inbreeding depression is as severe as in bunching onion.     

Application of in vivo and in vitro mutation techniques for crop improvement

Summary Conventional mutation techniques have often been used to improve yield, quality, disease and pest resistance in crops, or to increase the attractiveness of flowers and ornamental plants. More than 1700 mutant varieties involving 154 plant species have been officially released. In some economically important crops, e.g. barley, durum wheat and cotton, mutant varieties occupy the majority of cultivated areas in many countries. Mutation techniques have become one of the major tools in the breeding of ornamentals such as alstroemeria, begonia, chrysanthemum, carnation, dahlia and streptocarpus. The use of in vitro techniques such as anther culture, shoot organogenesis, somatic embryogenesis and protoplast fusion can overcome some of the limitations in the application of mutation techniques in both seed and vegetatively propagated crops. In vitro culture in combination with induced mutations can speed up breeding programmes, from the generation of variability, through selection, to multiplication of the desired genotypes. The expression of induced mutations in the pure homozygote obtained through microspore, anther or ovary culture, can enhance the rapid recovery of the desired traits. In some vegetatively propagated species, mutations in combination with in vitro culture technique, may be the only method of improving an existing cultivar. Currently, many molecular studies rely on the induction and identification of mutants in model species for construction and subsequent saturation of genetic maps, understanding of developmental genetics and elucidation of biochemical pathways. Once identified and isolated, the genes that encode agronomically-important features can be either introduced directly into crop plants or used as probes to search for similar genes in crop species. It seems most likely that the recent developments based on these technologies will soon provide improved methods for selection of desired mutants.     

Developmental abnormalities in the ovule and embryo sac of ulluco (Ullucus tuberosus) and their effect on seed set

Summary Ulluco (Ullucus tuberosus) is a vegetatively propagated crop plant that flowers abundantly but sets only few seeds. We examined if the low seed/ovule ratio can be explained by morphological abnormalities in ovules, embryo sacs or embryos. In 35 clones growing in the actual area of cultivation in Ecuador and in 5 clones grown in Finland flowers were analysed by clearing technique. About half of all analysed clones contained ovules and embryo sacs whose development was arrested, in two clones there were embryo sacs whose cell patterns were abnormal and in four clones there were double embryo sacs. There were both normal and abnormal ovules and embryo sacs in the same plant. Genetic load is suggested to be one of the causes for the low sexual fertility found in ulluco. It may be incapable of maintaining homeostasis of development of the ovule and embryo sac in a varying environment. The occurrence of developmental abnormalities should be studied in each clone intended for inclusion in traditional breeding programmes.     

Diversity of white and narrow-leafed lupin genotype adaptive response across climatically-contrasting Italian environments and implications for selection

White lupin (Lupinus albus) and narrow-leafed lupin (L. angustifolius) have special interest as high-protein feed crops but their cultivation is limited by low grain yields. This study aimed to support breeding programs targeting Italy or other climatically variable south-European regions by investigating within-species adaptation patterns across contrasting Italian environments. An additional aim was comparing species for yielding ability. Eight narrow-leafed and six white lupin cultivars featuring different origin, phenological type (Mediterranean in both species; winter in white lupin; spring in narrow-leafed lupin) and plant architecture (determinate or indeterminate in both species; tall or dwarf in white lupin) were evaluated in a Mediterranean and a subcontinental-climate site under autumn and late-winter sowing. Additive main effects and multiplicative interaction was preferable to joint regression for modeling yield responses. In both species, cross-over GE interaction was observed (P < 0.05), autumn-sown Mediterranean and subcontinental environments were the most-contrasting for GE effects, and widely adapted material included cultivars of Mediterranean phenological type with indeterminate growth. Material with determinate growth was not among the best-yielding entries in any environment, whereas a dwarf winter-type white lupin entry was specifically adapted to autumn-sown subcontinental environments. White lupin displayed larger genetic variation than narrow-leafed lupin for phenology and other traits. Relationships of morphophysiological traits with grain yield were environment-specific and were locally high for some white lupin traits (early flowering, long reproductive phase, high aerial biomass, low proportion of pod wall). White lupin exhibited higher yielding ability than narrow-leafed lupin in all environments but the late-winter sown Mediterranean one, when comparing locally top-yielding cultivars.     

Effect of tissue culture explant source on sugarcane yield components

Clonal propagation of sugarcane(interspecific hybrids of Saccharum)is conducive to spread of systemicdiseases, such as ratoon stunting disease,caused by Leifsonia xyli subsp. xyli. This important disease iscontrolled by obtaining and plantinghealthy seed-cane. In Louisiana, commercialseed-cane initially produced through tissueculture is available to sugarcane farmersand is being widely planted. Long-termacceptability of this seed-cane productionmethod depends on the production of healthyplants that do not differ significantly inphenotypic and yield characteristics fromthe clones originally selected and releasedas commercial cultivars. To determinewhether tissue culture affects yield or itscomponents, three cultivars, CP 70-321, LCP85-384, and HoCP 85-845, were compared inthree successive crops initially plantedwith stalks from three sources: plantsderived from callus culture of the leafroll above the apical meristem, directregeneration from the apical meristem, andconventional bud propagation. Stalks ofplants derived from both explant sourceswere typical of seed-cane farmers wouldpurchase for planting that had beenpreviously rogued for phenotypic variantsand increased by bud propagation.Differences in yield components amongtissue culture explant sources and budpropagated cane only occurred in CP 70-321.Stalk diameter and stalk weight were lowerand stalk population was higher for plantsderived from leaf roll callus compared tobud propagated cane. Yield components weresimilar for plants derived from an apicalmeristem and bud propagation. Individualplant phenotypic variants resulting fromsomaclonal variation were not observed inany of the cultivars derived from eitherexplant source. In summary, genotype andexplant source affected persistent, uniformphenotypic variation resulting from tissueculture that changed some yield components. However, apical meristem culture wassuitable for production of seed-cane, assugarcane derived by meristem culture ofthree cultivars did not differsignificantly from the original germplasmfor any measured yield trait.     

Plant breeding: past,present and future

Plant breeders can help farmers increase food production by breeding new cultivars better adapted to their chosen farming systems, but these must be capable of providing the necessary plant inputs for the required levels of crop production in 2050. Until 200 years ago the farmers themselves were the plant selectors. Plant domestications, extensive crop dispersions and farmers’ selections produced thousands of locally adapted landraces of cultivated plants. During the twentieth century these were largely replaced by relatively few high yielding cultivars and the natural habitats of many of their wild relatives became endangered. Hence in situ and ex situ conservation, and evaluation and use of plant genetic resources is vital for future plant breeding. The development of scientific breeding from the beginning of the twentieth century was based on understanding the mechanism of inheritance and the mating systems of crop plants. The types of genetically uniform, high yielding cultivars that have been bred from genetically heterogeneous landraces were determined by the mode of reproduction and mating system of the cultivated plant species: inbred line (wheat) and hybrid (rice) cultivars for inbreeding species, hybrid (maize) cultivars for outbreeding species, and clonal (potato) cultivars for vegetatively propagated species. When genetically heterogeneous crops are desired, mixtures of cultivars and synthetic cultivars can be produced. Future progress in crop improvement will come from three complementary approaches: use of hybridization and selection in further conventional breeding, base broadening and introgression; mutation breeding, cisgenesis and gene editing; and genetically modified crops.     

Alteration of methylation profiles in distinct cell lineages of the layers during vegetative propagation in carnations (Dianthus caryophyllus)

In vegetatively propagated plants, branches of periclinal chimera give rise to bud mutants, or “sports”, which have been used to breed new cultivars. Here, we have examined DNA methylation profiles in the cells of the L1 and L2+3 layers from single plants of vegetatively propagated carnations. The band patterns of methylation-sensitive amplified fragment polymorphism (M-AFLP) of the genomic DNAs in the L1 and L2+3 layers of the carnation cultivar, “White Sim”, vegetatively propagated over the past 50 years, were completely different. The bud mutant, “White Mind”, obtained from “White Sim” about 25 years ago, also had very different M-AFLP patterns to the parental “White Sim” line. The cultivar, “Red”, which was separated from “Satisfaction” as a bud mutant two years ago, showed similar patterns to “Satisfaction” in each corresponding layer. However, we were able to detect minor, but significantly different M-AFLP patterns between the cultivars, “Red” and “Satisfaction”. The number of bands that differed between these cultivars was larger in the L2+3 layers than in the L1 layers. The results indicate that the DNA methylation profiles differ between each cell layer derived from distinct cell lineages of vegetatively propagated plants, and that changes in these profiles occur frequently and accumulate in the cells of the L2+3 layers, rather than in the L1 layer. This revised version was published online in July 2006 with corrections to the Cover Date.     

Introgression from wild Cicer reticulatum to cultivated chickpea for productivity and disease resistance

Interspecific hybridization is known to improve productivity and resistance to diseases in many crops. Therefore, an attempt was made to introgress productivity and disease resistance into chickpea from wild Cicer species. The true F₁ hybrids of cultivated chickpea genotypes ‘L550’ and ‘FGK45’ with C. reticulatum were backcrossed twice to their cultivated female parents to minimize the linkage drag of undesirable wild traits. The pedigree method was followed to advance the segregating populations from straight crosses (without backcross) and BC₁/BC₂ generations to F₅–F₇. The interspecific derivatives recorded up to a 16.9% increase over the check cultivars and a 25.2% increase over the female parent in a preliminary yield evaluation trial. Of the 22 interspecific derivatives thus derived, four desi and two kabuli lines were further evaluated for seed yield in replicated trials at three diverse locations. These lines possess a high degree of resistance to wilt, foot rot and root rot diseases, and recorded a 6.1–17.0% seed yield increase over the best check cultivars.     

Simplified AFLP procedure as a tool for identification of strawberry cultivars and advanced breeding lines

DNA polymorphisms among 6 cultivars of Fragaria × ananassa (Duch.) and 13salinity tolerant clones were evaluated using simplified – PstI based Amplified Fragment Length Polymorphism procedure(^PstIAFLP). Out of 129 amplification products obtained with 10 selective primers, 116 markers were polymorphic and could be used to distinguish all analyzed materials. Coordinate and cluster analyses revealed 2 main groups of clones and divided strawberry cultivars (CUL) and tested F₁ hybrids of ‘Sweet Heart’(HYB). Mean genetic similarities in groups of cultivars and selected breeding lines (SEL) were significantly higher (0.722 and0.706, respectively, p < 0.05) than in group of SH hybrids (0.485). Results suggest that ^PstIAFLP method is sufficient for effective identification and useful for assessing the level of genetic diversity in strawberry cultivars and breeding lines. The presented method can bean alternative multilocus marker system to widespread RAPD method. This revised version was published online in July 2006 with corrections to the Cover Date.     

Improved drought tolerance and root development as components of a scheme to breed blueberries for mineral soil adaptability

Blueberry breeding in North America started at the beginning of the 20th century and present cultivars are adapted to irrigated, high organic, acidic, sandy soils. However, sites meeting these requirements are limited, which has forced breeders to develop germplasm that is adapted to unamended mineral soils. Wild Vaccinium species can be found growing on a number of different soil types under a variety of climatic conditions, which indicates that genetic variability for mineral soil adaptability is present in Vaccinium germplasm. However, for a number of reasons progress in the development of mineral soil-adapted blueberry cultivars has been slow. In this paper a breeding scheme is presented that would allow the user to more efficiently access the variability that exists for mineral soil adaptability. The scheme is composed of two different seedling screening techniques (drought and seedling rooting screen) that are designed to eliminate the less vigorous individuals in a population before field testing. The field environment would be used primarily to evaluate individuals for fruit quality and yield characteristics. In blueberries, both general and specific combining ability can be fully exploited because they are vegetatively propagated which immediately fixes any unique combination of genes.     

Significant effect of accidental pollinations on the progeny of low setting Prunus interspecific crosses

The incidence of fortuitous pollination on interspecific hybridizations of the plum rootstock Myrobalan with the apricot cultivars ‘Moniquí’ and ‘Moniquí Borde’ was assessed in this work. Progeny was originated through hand pollination of emasculated flowers of three Myrobalan clones, without bagging, in 1998 and 1999. Fruit set was low and variable among years (1.8–8.0%), but higher than the level of accidental pollination measured with emasculated and non-pollinated flowers (1.2%). Molecular characterization of the progeny was performed with three SSR markers showing that only 28% of the seedlings, obtained by in vitro germination and culture of immature embryos, were hybrids. This represents a lower percentage than expected, and is explained here by the low viability of hybrid embryos and seedlings. The use of molecular markers is discussed in terms of a convenient method for an early identification of putative hybrids in breeding programs with low setting crosses, where the proportion of non-hybrids is magnified.     

A practical method for apple cultivar identification and parent-offspring analysis using simple sequence repeat markers

Differentiation of cultivars with simple sequence repeat (SSR) markers is a very useful technique for the true-to-type characterization of cultivars and clarification of parent-offspring relationships. We developed an SSR marker set for cultivar identification comprising 15 markers that were screened from 46 previously published SSRs. This marker set could be used for apple varieties including Malus × domestica and/or other Malus species. These SSRs successfully characterized 95 apples, including the leading and major founding cultivars used worldwide for modern apple breeding. Therefore, this marker set could be applied to almost all apple cultivars. We also analyzed the parent-offspring relationships of 69 cultivars by considering allele transmissions. This analysis revealed the true parentage of the following seven cultivars: ‘Kizashi’, ‘Chinatsu’, ‘Honey Queen’, ‘Haruka’, ‘Seirin’, ‘Ozenokurenai’, and Morioka #48. This analysis also revealed a parentage discrepancy for ‘Hacnine’. From the parent-offspring analysis, two microsatellite mutation events at alleles inherited from pollen parents were observed.     

Analysis and Use of Interpool-Crosses (Mediterranean × Central European) in Faba Beans (Vicia faba L.) I. Performance of Mediterranean and Central European Faba Beans in Syria and Germany

The Central European and the Mediterranean Vicia faba gene pools carry different traits favourable for selecting cultivars with a high and stable yield performance. Interpool crosses, therefore, should provide interesting new basic material, although lack of adaptation of each “exotic” parent and linkage of genes may act against the introgression of favourable genes. In a first approach, five German and five Syrian parents (bred by ICARDA) of an interpool-crossing programme were tested in two years in both regions of origin. The Syrian cultivars proved to be fairly well adapted in the German trials, while the German cultivars were highly unadapted to the Syrian conditions. The advantage of interpool-crosses for both gene pools is discussed and recommendations on the further breeding strategy for adaptation of interpool-cross-progenies are given.     

Powdery mildew resistance in Kentucky bluegrass genotypes regenerated from excised seed pieces

Summary Severity of powdery mildew was assessed on seven cultivars and lines of Kentucky bluegrass propagated by seed and tissue culture. Tissue culture plants were started from embryo axes cultured on Murashige and Skoog medium containing different concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D) and 6-benzylaminopurine (BAP), and incubated (1 to 4 weeks) or not incubated in the dark prior to transfer to a lighted culture room. There were significant differences in disease severity (DS) among seed propagated and tissue culture regenerated plants. DS ranged from highly susceptible (100% of leaf covered by mildew) (DS=9) to resistant (DS=3.0). In some tissue culture regenerants the disease severity was significantly affected by the tissue culture process. Ten clones expressing resistance were selected, and plants propagated vegetatively. In six clones, disease resistance was sustainable in subsequent vegetatively propagated plants, while resistance was lost in four of the selected clones. Results are discussed with a view to using tissue culture to produce Kentucky bluegrass genotypes with resistance to powedery mildew.Abbreviations BAP benylaminopurine - 2,4-D 2,4-dichlorophenoxyacetic acid - DS disease severity - MS Murashige & Skoog - SDW sterile distilled water     

Identification of pathogenic races ofPhytophthora fragariae Hickman in Germany

Summary The fungusPhytophthora fragariae Hickman is the causal agent of red stele disease in strawberry (Fragaria × ananassa), this being a major disease in many areas with cool and moist conditions. Success of resistance breeding can be nullified by the appearence of specific races of the fungus capable of overcoming the introduced resistance. In some countries (USA, UK, Japan and Canada) races were identified by using a differential set of strawberry cultivars. The absence of an international standard differential set and the use of different test methods make a comparison of the identified races difficult or even lead to contradictory results for one variety/race combination. The aim of this study was to obtain information about the spectrum of pathogenic races in Germany as a basic contribution to research on resistance breeding against the fungus. The susceptibility of different strawberry cultivars to German isolates ofP. fragariae was evaluated. The inoculation was done by modifying a method described by Milholland et al. (1989). Rootedin vitro plants, four weeks after transferring them to the soil, were used for the investigation. Inoculation was done with a zoospore suspension of defined concentration. Up to now three German isolates, G-1, G-2, and G-3, can be separated by their ability to infect and produce oospores in the roots of the strawberry cultivars ‘Senga Sengana’, either ‘Saladin’, ‘Redgauntlet’ or ‘Climax’ andFragaria chiloensis clone ‘YaquinaB’. These results confirm the existence of pathogenic races ofP. fragariae in Germany and should be taken into consideration for resistance breeding against the fungus.     

Characteristics and inheritance of natural facultative-parthenocarpic fruit-set in ‘Nadja’ tomato under low temperature conditions

‘Nadja’ tomato (Lycopersicon esculentum Mill.) set both seedless and seeded fruits under the fluctuating temperatures prevailing during late-March and early-April in Assiut district, Egypt. Entirely seedless fruits developed under the low temperatures prevailing during Dec. Seedless fruits seemed to develop vegetatively , i.e. with no need for stimulus pollination. All seedless fruits were normally jelled and appeared similar in shape and size to the seeded fruits. Study of F₁, F₂, and backcross generations for the crosses ‘Cal Ace’ × ‘Nadja’ and ‘Peto-86’ × ‘Nadja’ suggested that the expression of the trait was due to single homozygous recessive gene. Yield produced by ‘Nadja’ was higher than the F₁, F₂, and backcross generations in both the early- summer and the late-winter plantings. Potentially useful parthenocarpic segregates were found in F₂ of the two crosses for increased fruit weight of normally shaped and jelled fruits. This revised version was published online in August 2006 with corrections to the Cover Date.     

Variation in virulence and resistance in the bean-bean rust pathosystem in Ecuador

Twenty two Uromyces appendiculatus isolates were tested on 20 differential and 25 Ecuadorian Phaseolus vulgaris cultivars in the seedling stage. Based on the infection types 20 races could be discerned. The Ecuadorian cultivars differed greatly in their reaction to the isolates, from resistant to only one isolate (`Red Small Garden') to resistant to all isolates (’G2333‘). The isolates showed a wide range of virulence to the Ecuadorian cultivars, from virulent to only two cultivars (isolate 13) to virulent to 21 cultivars (isolates 5 and 23). Seven cultivars with a basically susceptible infection type appeared to differ greatly in quantitative resistance when tested in three consecutive crop cycles. The disease severities in percentage leaf area affected averaged over the three cycles ranged between 83.9% for ‘Red Small Garden’ and 13.1% for ‘INIAP-414’. Race-specific resistance does not seem an advisable breeding strategy, but the quantitative resistance offers a good alternative.     

Zingiberene-mediated resistance to the South American tomato pinworm derived from Lycopersicon hirsutum var. hirsutum

The Lycopersicon hirsutum var. hirsutum accession PI 127826 is recognized as a good source of resistance to arthropod pests due to the action of the allelochemical zimgiberene, a sesquiterpene present in its glandular trichomes. Five genotypes were selected from the F₂ generation of the interspecific cross Lycopersicon esculentum ‘TOM-556’ × Lycopersicon hirsutum var. hirsutum ‘PI 127826’, based on their low levels (BPX-368-clone#56) or high levels(BPX-368-clone#92, BPX-368-clone#105,BPX-368-clone#179, BPX-368-clone#250) of zingiberene. The five F₂ genotypes were tested for resistance to the South American tomato pinworm Tuta absolutaalong with accession L. esculentum ‘TOM-556’ (pinworm susceptible), and the accessions L. hirsutum var. hirsutum ‘PI 127826’ and L. pennellii ‘LA716’ (resistant). The F₂ clones selected for high foliar zingiberene levels showed lower scores for leaflet lesion type(LLT), percent leaflets attacked (PLA) and overall plant damage (OPD) than the low zingiberene genotypes. The results indicated that zingiberene mediates resistance to the South American pinworm, based on feeding and on ovipositing deterrence, in populations derived from the interspecific cross between Lycopersicon. esculentum and Lycopersicon hirsutum var. hirsutum. Indirect selection for high foliar zingiberene content is suggested as an efficient technique for breeding tomatoes for resistance to the South American tomato pinworm. This revised version was published online in July 2006 with corrections to the Cover Date.