Bruce E. Urtz

Bio: Bruce E. Urtz is an academic researcher from Agricultural Research Service. The author has contributed to research in topics: Bassiana & Lissorhoptrus oryzophilus. The author has an hindex of 2, co-authored 2 publications receiving 93 citations. Previous affiliations of Bruce E. Urtz include North Carolina State University.

Genetic diversity among Bradyrhizobium isolates that effectively nodulate peanut (Arachis hypogaea)

Abstract: Symbiotic gene diversity and other measures of genetic diversity were examined in Bradyrhizobium isolates that form an effective symbiosis with peanut (Arachis hypogaea). Initially, restriction fra...

RAPD‐PCR characterization of Beauveria bassiana isolates from the rice water weevil Lissorhoptrus oryzophilus

Abstract: B.E. Urtz and W.C. Rice. 1997. Random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) was used to examine the genetic variability among Beauveria bassiana isolates from infected rice water weevil (RWW), Lissorhoptrus oryzophilus, collected in south-western Louisiana. Most of the B. bassiana isolates tightly clustered into one or the other of two groups that diverged at the 65% similarity level. Three soil isolates also clustered within the two groups while one soil isolate did not tightly cluster (mean similarity = 65%) with any of the RWW isolates. The results suggest that certain genotypes of B. bassiana commonly infect RWW while others do not.

Three phylogenetic groups of nodA and nifH genes in Sinorhizobium and Mesorhizobium isolates from leguminous trees growing in Africa and Latin America

Abstract: The diversity and phylogeny of nodA and nifH genes were studied by using 52 rhizobial isolates from Acacia senegal, Prosopis chilensis, and related leguminous trees growing in Africa and Latin America. All of the strains had similar host ranges and belonged to the genera Sinorhizobium and Mesorhizobium, as previously determined by 16S rRNA gene sequence analysis. The restriction patterns and a sequence analysis of the nodA and nifH genes divided the strains into the following three distinct groups: sinorhizobia from Africa, sinorhizobia from Latin America, and mesorhizobia from both regions. In a phylogenetic tree also containing previously published sequences, the nodA genes of our rhizobia formed a branch of their own, but within the branch no correlation between symbiotic genes and host trees was apparent. Within the large group of African sinorhizobia, similar symbiotic gene types were found in different chromosomal backgrounds, suggesting that transfer of symbiotic genes has occurred across species boundaries. Most strains had plasmids, and the presence of plasmid-borne nifH was demonstrated by hybridization for some examples. The nodA and nifH genes of Sinorhizobium teranga ORS1009T grouped with the nodA and nifH genes of the other African sinorhizobia, but Sinorhizobium saheli ORS609T had a totally different nodA sequence, although it was closely related based on the 16S rRNA gene and nifH data. This might be because this S. saheli strain was originally isolated from Sesbania sp., which belongs to a different cross-nodulation group than Acacia and Prosopis spp. The factors that appear to have influenced the evolution of rhizobial symbiotic genes vary in importance at different taxonomic levels.

Polyphasic evidence supporting the reclassification of Bradyrhizobium japonicum group Ia strains as Bradyrhizobium diazoefficiens sp. nov.

Abstract: Bradyrhizobium japonicum was described from soybean root-nodule bacterial isolates. Since its description, several studies have revealed heterogeneities among rhizobia assigned to this species. Strains assigned to B. japonicum group Ia have been isolated in several countries, and many of them are outstanding soybean symbionts used in inoculants worldwide, but they have also been isolated from other legume hosts. Here, we summarize published studies that indicate that group Ia strains are different from the B. japonicum type strain USDA 6T and closely related strains, and present new morphophysiological, genotypic and genomic evidence to support their reclassification into a novel species, for which the name Bradyrhizobium diazoefficiens sp. nov. is proposed. The type strain of the novel species is the well-studied strain USDA 110T ( = IAM 13628T = CCRC 13528T = NRRL B-4361T = NRRL B-4450T = TAL 102T = BCRC 13528T = JCM 10833T = TISTR 339T = SEMIA 5032T = 3I1B110T = ACCC 15034T = CCT 4249T = NBRC 14792T = R-12974T = CNPSo 46T).

Specificity in Legume-Rhizobia Symbioses.

Abstract: Most species in the Leguminosae (legume family) can fix atmospheric nitrogen (N₂) via symbiotic bacteria (rhizobia) in root nodules. Here, the literature on legume-rhizobia symbioses in field soils was reviewed and genotypically characterised rhizobia related to the taxonomy of the legumes from which they were isolated. The Leguminosae was divided into three sub-families, the Caesalpinioideae, Mimosoideae and Papilionoideae. Bradyrhizobium spp. were the exclusive rhizobial symbionts of species in the Caesalpinioideae, but data are limited. Generally, a range of rhizobia genera nodulated legume species across the two Mimosoideae tribes Ingeae and Mimoseae, but Mimosa spp. show specificity towards Burkholderia in central and southern Brazil, Rhizobium/Ensifer in central Mexico and Cupriavidus in southern Uruguay. These specific symbioses are likely to be at least in part related to the relative occurrence of the potential symbionts in soils of the different regions. Generally, Papilionoideae species were promiscuous in relation to rhizobial symbionts, but specificity for rhizobial genus appears to hold at the tribe level for the Fabeae (Rhizobium), the genus level for Cytisus (Bradyrhizobium), Lupinus (Bradyrhizobium) and the New Zealand native Sophora spp. (Mesorhizobium) and species level for Cicer arietinum (Mesorhizobium), Listia bainesii (Methylobacterium) and Listia angolensis (Microvirga). Specificity for rhizobial species/symbiovar appears to hold for Galega officinalis (Neorhizobium galegeae sv. officinalis), Galega orientalis (Neorhizobium galegeae sv. orientalis), Hedysarum coronarium (Rhizobium sullae), Medicago laciniata (Ensifer meliloti sv. medicaginis), Medicago rigiduloides (Ensifer meliloti sv. rigiduloides) and Trifolium ambiguum (Rhizobium leguminosarum sv. trifolii). Lateral gene transfer of specific symbiosis genes within rhizobial genera is an important mechanism allowing legumes to form symbioses with rhizobia adapted to particular soils. Strain-specific legume rhizobia symbioses can develop in particular habitats.

Insect-Fungal Associations: Ecology and Evolution

Abstract: There is a significant and increasing interest in using fungi as biocontrol agents for insect pests in agricultural systems, and also a growing interest in the basic biology of insect-fungal associations from the perspective of parasitism, symbiosis, and infection. Vega and Blackwell are well-regarded workers in this field, and they have assembled an impressive short book of ten chapters to cover the most important topics in this field, incorporating new molecular techniques wherever possible. The book should appeal to worker in ecology, entomology, mycology, plant pathology, and biological control and pest management.

DNA-DNA hybridization study of Bradyrhizobium strains

Abstract: DNA-DNA hybridizations were performed between Bradyrhizobium strains, isolated mainly from Faidherbia albida and Aeschynomene species, as well as Bradyrhizobium reference strains. Results indicated that the genus Bradyrhizobium consists of at least 11 genospecies, I to XI. The genospecies formed four subgeneric groups that were more closely related to each other (>40% DNA hybridization) than to other genospecies (<40% DNA hybridization): (i) genospecies I (Bradyrhizobium japonicum), III (Bradyrhizobium liaoningense), IV and V; (ii) genospecies VI and VIII; (iii) genospecies VII and IX; and (iv) genospecies II (Bradyrhizobium elkanii), X and XI. Photosynthetic Aeschynomene isolates were found to belong to at least two distinct genospecies in one subgeneric group. DNA-DNA hybridization data are compared with data from amplified fragment length polymorphism analysis and 165-23S rDNA spacer sequence analysis.