Tumorigenic Agrobacterium Research Articles

Evidence of migration and endophytic presence of Agrobacterium tumefaciens in rose plants

Agrobacterium tumefaciens was isolated from stem tumors of several rose cultivars showing that the bacterium is the causal agent of aerial galls in rose plants. No differences were observed in the characteristics of the Agrobacterium isolates from crown or aerial galls. Stem inoculation of ten rose cultivars showed that all of them were susceptible to A. tumefaciens but differences in the size of the resulting tumors were observed. The movement of A. tumefaciens in rose plants was demonstrated using two wild type strains and two antibiotic resistant mutants. Three months after inoculation, the inoculated strains were recovered in the roots, crown and below and above the inoculation site but low numbers of pathogenic Agrobacterium cells were isolated. New tumors appeared in 5% of the noninoculated wounds. A. tumefaciens was isolated from the stem at different distances from the tumor in naturally infected plants. In symptomless commercial plants, the isolation from the roots, crown and at different stem levels demonstrated the existence of systemic and latent infections in rose. Direct isolation using a nonselective and selective media with or without a previous enrichment step were efficient methods for isolating tumorigenic Agrobacterium from the different parts of rose plants.

STUDIES ON CAFFEA ARABICA GENETIC TRANSFORMATION

Attempts to transform somatic embryos of Caffea sp. with A.tumefaciens LBA44 04 pBI12l.l failed (C. Coyne and D. Lightfoot unpublished). In order to investigate the possibility of genotype interactions in Agrobacterium transformation of Caffea sp., leaf explants of the coffee cultivar Caturra were inoculated with 4 tumorigenic Agrobacterium strains. Callus formed on both control leaf explants and those inoculated with A. rhizogenes A4. However, callus did not continue autonomous growth when subcultured. The activity of 24 tumorigenic forming Agrobacterium strains was determined by inoculating the stems and leaves of kalanchoë, tomato, and carrot. Positive results were obtained with 14 strains. Three of these strains were genetically transformed by introducing the plasmid pBI121.1. Additional experiments on coffee leaf and internode explants inoculated with the 14 active Agrobacterium strains as well as the 3 transformed strains have been conducted.

根頭がんしゅ病菌のＴｉプラスミドに関連した表現形質による類別

根頭がんしゅ病菌のＴｉプラスミドに関連した表現形質による類別

Free amino acids of sunflower hypocotyl tissue during crown gall tumor development

The concentration of each free amino acid present in hypocotyl tissue of sunflower seedlings was determined during the period following both sterile wounding and inoculation with either tumorigenic (strain 1025) or non-tumorigenic (strain IIBNV6) Agrobacterium tumefaciens. The concentration of the total free amino acids of hypocotyl tissue reached a maximum 68 hours after infection with strain 1025 and this level was 50% greater than that found in plants treated with strain IIBNV6. The total content of free basic amino acids increased to a peak value at 20 hours after infection by strain 1025 and this represented 1.4 to 3 times the level found in strain IIBNV6 inoculated seedlings at 20 hours.The amount of free proline decreased with time and it was essentially absent 164 hours after infection with strain 1025. At 2 months the concentration of free proline in the tumor tissue was greatly increased with 75% of the total free amino acids accounted for as proline.The free amino acid content of strain 1025 growing in either the presence or absence of an extract from wounded seedlings was measured and the results indicated no significant relationship between the plant and bacterial systems with regard to their free amino acid pools.