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Carbohydrates, Ontogenesis, Phaseolus vulgaris L., Pseudomonas savastanoi pv. phaseolicola (syn. Pseudomonas syringae pv. phaseolicola), Resistance Physiological examination of resistant and susceptible bean genotypes has shown that the concentration and quantitative ratios of carbohydrates measurable in leaf tissues depend on the age of leaves. During the phases of ontogenesis, the glucose and sucrose levels are the lowest in the primary leaves and highest in the youngest upper leaf. There is a continuous increase in the concentration of both carbohydrates from the oldest to the youngest leaves. The glucose/sucrose quantitative ratio decreases with ageing of the leaves until blooming. Our results indicate that the glucose concentration decreases considerably in the susceptible bean leaves after infection with the bean pathogen Pseudomonas savastanoi pv. phaseolicola.It has been proved that the glucose plays an important role in the formation of the bacterial extracellular polysaccharide (E P S ) coat. Because there is a positive correlation between the age-dependent bacterial-resistance and the low sugar (especially glucose) content in older leaves of the originally susceptible bean plant, we think that in the old leaves there is not enough glucose for production of the EPS coat. Lacking E PS coat the bacterial and plant cell walls come in direct contact which permits the induction of hypersensitivity response characteristic of resistance.

Nine genotypes of melon (Cucumis melo L.) were selected for the investigation of regeneration. Most of the tested varieties showed regeneration ability on medium containing 0.5 mg l⁻¹ or 1 mg l⁻¹ BA, but following the appearance of shoot buds, only six varieties produced leafy shoots. The effect of combinations of BA with different auxins (IAA, NA, 2,4-D) and ABA in the culture medium on shoot regeneration was tested on cotyledon explants of 'Hógolyó' and 'Hale's Best'. To establish optimal conditions for the adventitious shoot induction six types of seedling-derived explants were prepared from seedlings of four different ages. The best results for shoot forming capacity were achieved with cotyledons followed by decapitated seedlings and hypocotyls derived from 4-day-old seedlings. Cotyledon segments of 'Hógolyó' and 'Hale's Best' were also cultivated on media with different concentrations of IAA and BA supplemented with 0.26 mg l⁻¹ ABA. The highest number of well-formed plantlets was counted for 'Hógolyó' on the medium supplemented with 0.9 mg l⁻¹ BA+ 0.6 mg l⁻¹ IAA+ 0.26 mg l⁻¹ ABA. This is the first report on the in vitro regeneration of 'Hógolyó' from decapitated seedling and hypocotyl explants and of 'JavÍtott Zentai', 'Muskotály', 'Hógolyó', 'Tétényi csereshéjú' and 'Magyar Kincs' from cotyledon explants.

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