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This study analyzes the morphological and genetic characteristics of three sympatric populations of Prosopis from Argentina. Although morphological and geographical data suggest that Prosopis chilensis var. riojana is an interspecific hybrid of Prosopis chilensis var. chilensis and Prosopis flexuosa var. flexuosa, no correlation was found between morphological traits and genetic distances generated by random amplified polymorphic DNA - polymerase chain reaction (RAPD-PCR). Genetic similarity is greater among P. chilensis var. chilensis and P. flexuosa var. flexuosa than between either of these two taxa with P. chilensis var. riojana. Also, P. chilensis var. riojana has unique genetic markers that are absent from its putative parents. Additionally, dendrograms generated by unweighted pair group method with arithmetic means (UPGMA) and Neighbor-Joining clustering criteria group P. chilensis var. chilensis and P. flexuosa var. flexuosa apart from P. chilensis var. riojana. Possibilities for the lack of congruence between morphology and RAPD markers are discussed. The results obtained are insufficient to conclusively establish the origin of P. chilensis var. riojana; however, the morphological and genetic traits observed suggest this taxon is well differentiated from P. chilensis var. chilensis and P. flexuosa var. flexuosa. [ABSTRACT FROM AUTHOR]

Presents a study which examined the isolation of DNA from forest soil suitable for polymerase chain reaction assays of fungal and plant rRNA genes. Uses of the obtained DNA; Review of related literature; Analysis of DNA and amplification products; Steps required to obtain good genomic material.

White rot caused by the fungus Sclerotium cepivorum causes great economic losses in the genus Allium nationwide. In this work, three rhizobacteria with antagonistic effect on this fungus were isolated, identified and characterized. 656 bacteria were isolated in soil samples from the rhizosphere of onion plants (Allium cepa). And in vitro antagonism to S. cepivorum was also evaluated. 23 of these isolates showed antagonistic activity with inhibition halos greater than 5 mm; three of these were greater than 20 mm; these were selected and identified as Gram positive bacilli, belonging to the genus Bacillus, B. amyloliquefaciens and B. subtilis. These rhizobacteria showed enzymatic activity of 1-aminocyclopropane 1-carboxylate deaminase, production of indolacetic acid and siderophores, as well as NaCl tolerance (up to 7.5%). Temperatures of 24 and 37 °C and humidity (50, 75 and 100%) did not affect bacterial development. Of the cellfree extracts obtained in different growth phases, the highest antifungal activity on S. cepivorum was obtained with the stationary phase extracts (16 to 24 h of incubation). Due to the attributes of these rhizobacteria they could be considered as an alternative for the control of S. cepivorum in onion. [ABSTRACT FROM AUTHOR]