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Abstract
The trend towards total mechanization of the production of processing tomatoes is creating many new problems. This paper describes one which may become very important as the practice of direct seeding in the field partly replaces the use of transplants.
Abstract
The potato aphid (Macrosiphum euphorbiae) is a common insect pest of tomatoes. This insect damages the plants by sucking the sap from the leaves and by transmitting plant viruses The severity of aphid infestations on tomatoes varies from season to season and within a season. They are generally most severe during periods of cool weather.
Abstract
When cultivars and accessions of the cultivated tomato, Lycopersicon esculentum Mill., and related species, were evaluated for resistance to a leaf miner, Liriomyza munda Frick, in greenhouse and field cage tests, the screening tests revealed several lines of L. esculentum having genes for adult nonpreference or larval antibiosis or both. All accessions of L. hirsutum Humb. & Bonpl. and L. hirsutum f. glabratum C. H. Mull, were virtually immune to attack in both greenhouse and field tests. Lycopersicon pimpinellifolium (Jusl.) Mill, demonstrated a considerable level of antibiosis in the greenhouse, but was not promising in the field. All accessions of L. peruvianum var. dentatum Dun. and L. glandulosum C. H. Mull, tested were susceptible. The commercial cv. VF 145B was nonpreferred in the field.
Protoplasts isolated from an embryogenic callus line of `Femminello siracusano' lemon [Citrus limon (L.) Burm. f.] were incubated with 0.5 μm toxin of Phoma tracheiphila (Petri) Kanc. et Ghik., the pathogen of the mal secco disease, which seriously damages most commercial lemon cultivars. Two toxin-tolerant cell lines were obtained, and plants were regenerated from each line. The selected protoclones were tested for their tolerance by exposing callus and protoplasts to the toxin and detecting chitinase (a pathogenesis-related protein) among the intra- and extracellular proteins extracted from leaves of regenerated plants and suspension culture, respectively. The tolerance of the protoclones in these tests was equivalent to the tolerant lemon cultivar Monachello, and they were substantially more tolerant than their mother cultivar Femminello siracusano.
Abstract
Accessions, breeding lines, and varieties of Lycopersicon spp. and one accession of Solarium pennellii Correll were evaluated for sensitivity to controlled concentrations of O3 and to ambient air at Waltham, Massachusetts. The plant material was exposed in different stages of development to controlled O3 concentrations of 0.25 ppm for 3 hours, 0.05 ppm for 2 weeks and to 0.10 ppm for 4 weeks. Based upon the degree of foliar injury, the tested material was separated into tolerant, intermediate and sensitive populations. The highest degree of tolerance was observed in L. esculentum Mill, and the highest degree of sensitivity in L. pimpinellifolium. Germination of pollen from inflorescences exposed to 0.10 ppm was reduced 40% in sensitive accessions of L. pimpinellifolium when placed on artificial medium. No significant reduction was observed in the most tolerant accession of L. esculentum. Differences in percent germination were not observed when pollen of sensitive and tolerant accessions was placed on artificial medium and exposed to 0.10 ppm O3 for a six-hour period. Reciprocal cross pollinations between exposed and unexposed populations led to normal fruit development with viable seeds.