Graduate Thesis Or Dissertation

 

A survey of Agrobacterium strains associated with Georgia pecan trees and an immunological study of the bacterium Public Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/b8515r794

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  • Crown gall was found in numerous pecan orchards in Georgia. In some instances, 60% of the trees were diseased. Galled trees were less vigorous than noninfected trees. Among the pathogenic Agrobacterium strains isolated from 18 galled trees from six counties, biovar 1 strains predominated and most were sensitive to agrocin 84 in vitro. A representative biovar 1 strain from pecan was inhibited from infecting tomato seedlings by A. radiobacter K84. We would expect that biological control of crown gall in Georgia pecan orchards with strain K84 would be successful. Because the taxonomy of the members of the Rhizobiaceae has not been resolved by classical and modern methods of microbial classification, a serological analysis of the 50S ribosomal subunits was made. Antisera raised against 50S ribosomal subunits of five different agrobacteria were used to arrange 31 Agrobacterium strains and 6 Rhizobium strains into 16 serovars. The immunological relationships of 50S subunits of Agrobacterium did not confirm either of the major taxonomic groupings; fast-growing rhizobia could not be immunologically differenciated from the agrobacteria and were closely related to the biovar 3 strain CG64. The five antisera were specific at the family level. The antigenic structure of 50S ribosomal subunits of tumorigenic strain C58 and rhizogenic strain A4 were compared to that of their avirulent derivatives (NT1 and A4R1, respectively) and to strain A323 (A NT1 that was transformed with the large nopaline plasmid from K84) using Ouchterlony doubly diffusion tests. A unique precipitin band was observed with 50S subunits of the virulent piasmid-containing strains; this band which revealed the presence of an additional immunogen was absent from 50S subunits of the plasmid-deficient mutants. This unique band observed in 50S subunits of the virulent strain C58 was also present in the transformant A323, but was absent from both strains NT1 and K84. Therefore, it appears that the combination of plasmid and chromosome can induce formation of new 50S ribosomal subunits which have a major immunological difference from 50S subunits of cells of the same chromosomal background but lacking the plasmid.
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