The salinity tolerances of 21 accessions belonging to four wild tomato species [Lycopersicon pimpinellifolium (Jusl.) Mill., L. peruvianum (Corr.) D'Arcy, L. hirsutum (L.) Mill., and L. pennellii Humb. Bonpl.) were evaluated using their vegetative yield-salinity response curves at the adult stage, determined by a piecewise-linear response model. The slope (yield decrease per unit salinity increase), salinity response threshold, maximum electrical conductivity without yield reduction (ECo), and salinity level for which yield would be zero (ECo) were determined by a nonlinear least-squares inversion method from curves based on the response of leaf and stem dry weights to substrate EC. The genotype PE-2 (L. pimpinellifolium) had the highest salt tolerance, followed by PE-45 (L. pennellii), PE-34, PE-43 (L. hirsutum), and PE-16 (L. peruvianum). The model also was tested replacing substrate salinity levels with leaf Cl- or Na+ concentrations. Concentrations of both ions for which vegetative yields were zero (Clo and Nao) were determined from the response curves. In general, the most tolerant genotypes were those with the highest Clo and Nao values, suggesting that the dominant salt-tolerance mechanism is ion accumulation, but there were cases in which salt tolerance was not related to Clo and Nao.
M.C. Bolarín, F.G. Fernández, V. Cruz, and J. Cuartero
S.J. Scott, M. Stevens, and R.C. Gergerich
Three methods to inoculate Lycopersicon esculentum 'VF Pink' seedlings with tomato spotted wilt virus (TSWV) were compared. Treatments were 1) two inoculations by hand (rubbing leaves with a sterile cotton swab), 2) a single inoculation using a paint sprayer at 3.56 × 105 N· m-2, and 3) two spray inoculations. All three methods were effective (>95% infection) under moderate temperatures in the spring, but hand inoculation was not effective under hot conditions in the summer. In another experiment, spray inoculation was used to compare effects of light intensity and the leaf inoculated on susceptibility of L.. hirsutum PI 127826, L. pimpinellifoliom LA 1580 and `VF Pink' to TSWV isolate 85-9. All three genotypes were susceptible under full sun and 60% shade cloth in the greenhouse. Inoculation of youngest leaves produced the highest virus titer. Background optical density for noninoculated plants differed between lower and upper leaves in the ELISA assay.
Richard W. Robinson
Bumblebees are commercially used to improve fruit set of greenhouse tomatoes, but they seldom pollinate tomatoes outdoors if not confined in a no-choice situation. Bumblebees frequently pollinated L. peruvianum and other self-incompatible (SI) Lycopersicon species, but not tomato plants, in the field at Geneva, N.Y. Bumblebees were very efficient pollinators of Sl Lycopersicon species, averaging only 5 s to pollinate one flower and fly to the next. Transfer of this attractiveness to pollinating insects to the tomato could improve fruit set of tomatoes grown in greenhouses with introduced bumblebees. It could also improve fruit set in the field, especially when conditions are poor for pollination. It has potential use for producing F1 hybrid seed, but associated problems make hybrid tomato seed production by insect pollination impractical now. Attractiveness to pollinating insects is being introgressed from L. peruvianum, L. hirsutum, and L. pennellii in the tomato breeding program at Geneva, N.Y. Several floral characteristics were found to be of importance for attracting pollinators, including the reaction to ultraviolet light. Flowers of SI species absorbed UV, whereas tomato flowers reflected UV light.
John A. Juvik
Heliothis zea (Boddle) is one of agriculture's worst insect pests. Reduction in crop productivity and costs for insecticidal control of this cosmopolitan pest cost U.S. agriculture many millions of dollars annually. The sesquiterpenes (+)-E-å-santalen-12-oic and (+)-E- endo- β–bergamoten-12-oic acids isolated from hexane leaf extracts of the wild tomato species, Lycopersicon hirsutum, have been shown to attract and stimulate oviposition by female H. zea. Extracts from other host plants (tobacco, corn, and cotton) also possess attractant/oviposition stimulant activity to female H. zea. Studies are underway to assess the potential use of these and other phytochemicals for the control or monitoring of population levels of H. zea in tomato, corn and cotton fields.
The isolation and structural identification of insect pest oviposition stimulants in horticultural crop species can provide valuable information to plant breeders involved in developing cultivars with improved insect host plant resistance. This information could be used to develop cultivars lacking the chemical cues used by insects for host plant location and recognition. Risks of public exposure to toxic insecticides through consumption of agricultural produce and polluted ground water emphasize the critical need for the development of crop genotypes with improved best plant resistance as a supplementary method of insect pest management in agricultural ecosystems.
John R. Stommel, Judith A. Abbott*, David Francis, and Mary J. Camp
Tomato fruit firmness is a key quality component of tomatoes produced for processing applications. Fruit firmness is generally considered a quantitatively inherited trait. Pericarp firmness of modern tomato cultivars is believed to be derived from a fairly narrow genetic background and is the result of the cumulative effort of numerous breeders over many years. Despite inferior phenotypes, wild species contain loci that can substantially increase tomato fruit quality. In the current study, inheritance of fruit firmness in firm and ultra-firm processing tomato germplasm developed from transgressive segregants of interspecific Lycopersicon esculentum × L. hirsutum and intraspecific L. esculentum crosses was characterized. Large-fruited breeding lines that varied in fruit firmness from soft to firm were identified for genetic analyses. A six-parent diallel of these advanced breeding lines was developed for field trials over multiple locations. Fruit firmness in the resulting 36 lines was determined by measuring fruit elastic properties during fruit puncture and compression. Following loading for compression, stress relaxation was recorded for 15 s. A three-parameter model was used to fit the relaxation curves. There was little correlation between firmness (maximum force) and the three relaxation parameters, i.e., firmness measured the elastic component and the relaxation parameters measured the viscous portions of the texture. General and specific combining ability for firmness derived from the respective genetic backgrounds was determined. Genetic variance components for fruit firmness were estimated using a diallel analysis and narrow sense heritability was measured using parent-offspring regression.
James E. Frelichowski and John A. Juvik
Sesquiterpene carboxylic acids (SCA) are synthesized by leaf trichomes of a wild tomato species Lycopersicon hirsutum accession LA 1777 and confer resistance to the tomato pests Helicoverpa zea (Boddie) and Spodoptera exigua (Hubner). Larvae of both species exhibited a reduction in survival and growth rate with altered feeding behavior when exposed to SCA in choice and no-choice insect bioassays. Larvae of both species were reared on artificial insect diets with SCA added at 0, 10 and 60 mg SCA per g of diet. All larvae perished in the 60 mg·g–1 treatment which is comparable to the levels of SCA found on LA 1777. H. zea and S. exigua showed about 35% and 60% reduction in survival to adult and 38% to 22% increase in life cycle duration, respectively, in the 10 mg·g–1 treatment relative to the control. Similar reductions in growth rate and survival were observed when larvae were reared on leaves coated with SCA. Choice bioassays with control (0 mg SCA/g leaf) and 60 mg SCA/g treated leaf tissue demonstrated 2.3-fold increase in larval avoidance and 50% reduction in feeding on treated leaves. Our results suggest that breeding for SCA synthesis in tomato would produce lines with increased resistance to the tomato pests H. zea and S. exigua. Backcross breeding procedures using LA 1777 have initiated the introgression of the SCA genes into cultivated tomato germplasm. Studies of inheritance of genes coding for SCA synthesis are underway to reveal allelic interactions and facilitate there introgression into the cultivated tomato germplasm.
Peter M. Hanson, Dario Bernacchi, Sylvia Green, Steven D. Tanksley, Venkataramappa Muniyappa, Attiganal S. Padmaja, Huei-mei Chen, George Kuo, Denise Fang, and Jen-tzu Chen
Tomato yellow leaf curl virus (TYLCV), a heterogeneous complex of whitefly-vectored geminiviruses, is a serious production constraint of tomato (Lycopersicon esculentum Mill.) in Asia, the Middle East, and the Americas. In this study we report on mapping of a DNA fragment introgressed into cultivated tomato presumably from the wild species L. hirsutum Humb. and Bonpl. and found to be associated with TYLCV resistance. To locate introgressions of wild tomato alleles in TYLCV-resistant tomato line H24, its DNA was digested with six restriction enzymes and probed with 90 RFLP markers evenly spaced throughout the genome. This polymorphism survey revealed the presence of one wild tomato introgression each on chromosomes 8 and 11. Plants of a F2 cross between H24 and a susceptible tomato line were probed with randomly amplified polymorphic DNA (RFLP) markers linked to the targeted regions and F3 families were developed by self-pollination of F2 plants that carried none, one, or both introgressions in either homozygous or heterozygous states. Plants of F3 families, parents, and control tomato line Ty52 (homozygous for the Ty-1 allele for TYLCV tolerance) were exposed to viruliferous whiteflies (Bemisia tabaci Gennadius) in greenhouses at the Asian Vegetable Research and Development Center, Taiwan, and the University of Agricultural Sciences, Bangalore, India. Results indicated that F3 families homozygous for the introgression on chromosome 11 were resistant to TYLCV at both locations. Additional probing showed that the chromosome 11 introgression spanned markers TG36 to TG393, covering a distance of at least 14.6 centimorgans. This is the first report of TYLCV resistance in tomato mapped to chromosome 11.
Aliya Momotaz, John W. Scott, and David J. Schuster
. Literature Cited Banerjee, M.K. Kallo, G. 1987 Inheritance of tomato leaf curl virus resistance in Lycopersicon hirsutum f. glabratum Euphytica 36 581 584 Bernacchi, D. Tanksley, S.D. 1997
Aliya Momotaz, Jay W. Scott, and David J. Schuster
Inheritance of sesquiterpene carboxylic acid synthesis in crosses of Lycopersicon hirsutum with insect-susceptible tomatoes Plant Breed. 124 277 281 Fridman, E. Wang, J. Lijima, Y. Froehlich, J.E. Gang
Oğuz Top, Cantuğ Bar, Bilal Ökmen, Duygu Yüce Özer, Dane Rusçuklu, Nilüfer Tamer, Anne Frary, and Sami Doğanlar
carrying new root-knot nematode resistance genes Euphytica 95 203 207 Francis, D.M. Kabelka, E. Bell, J. Franchino, B. St. Clair, D. 2001 Resistance to bacterial canker in tomato ( Lycopersicon hirsutum LA407) and its progeny derived from crosses to L