Interaction ofErwinia spp. andFusarium roseum ‘Sambucinum’ on the Russet Burbank potato

Laboratory and field studies with the Russet Burbank (RB) potato provide evidence for synergism betweenErwinia carotovora var. atroseptica (Ea) andFusarium roseunt ‘Sambucinum’ (Fs). When these pathogens were inoculated together, the severity of tuber rot was significantly greater than when either pathogen was inoculated separately. Similarly, these pathogens interacted to reduce yield. When both organisms were uniformly applied to puncture wounds on potato seed (inoculum suspension consisted of 10⁸ cells/ml Ea and 10⁵ cells/ml Fs), the total yield was reduced by 46% and U.S. #1 yield by 53%. These reductions occurred even though blackleg symptoms (caused by Ea) were negligible (< 1%). In contrast, inoculations withErwinia carotovora var.carotovora (Ec) and Fs did not interact to reduce potato yield. Potato yields were also not influenced when these pathogens (Ea, Ec, Fs) were separately inoculated.Verticillium wilt (Verticillium dahliae) was significantly less when tubers were inoculated with either Ea, Ec, Fs, Ea + Fs, or Ec + Fs than with uninoculated tubers.     

Biological control of fusarium dry rot of potato tubers under commercial storage conditions

Lack of effective chemicals impedes control of Fusarium dry rot of stored potato tubers destined for processed and table stock use. Biological control of dry rot incited byGibberella pulicaris (anamorph=Fusarium sambucinum) has been demonstrated in laboratory studies but not in commercial storage environments. Several Gram-negative bacterial strains that were efficacious and amenable to production in liquid culture in laboratory studies were selected for pilot studies in Idaho and for bin trials at commercial storage houses in Idaho and North Dakota. In the first year of pilot studies,Pseudomonas fluorescens S22:T:04 (≈1 x 10⁸ cfu/ml) decreased dry rot caused byG. pulicaris by 19% when coinoculated with the pathogen compared to controls and to the fungicide thiabendazole (TBZ) applied at label rates. In second year pilot studies,P. fluorescens P22:Y:05 andEnterobacter cloacae S11:T:07 (≈4 x 10⁸ cfu/ml) reduced the severity of disease incited byG. pulicaris (25% and 17% average disease decrease, respectively) when antagonists were applied after pathogen inoculum. Treatment effects on dry rot that developed from inoculation withNectria haematococca (anamorph=Fusariumsolani var.coeruleum) were variable and influenced by interactions between antagonists, a wetting agent, and TBZ. In commercial storage bin trials,E. cloacae S11:T:07 reduced naturally occurring levels of dry rot by an average of 21% compared to 14% for TBZ, demonstrating that this antagonist was effective when produced using a liquid culture medium and methodology that approximates commercial practices for producing biomass.     

Molecular characterization and genetic relatedness among walnut (Juglans regia L.) genotypes based on RAPD markers

The potential use of the Randomly Amplified Polymorphic DNA (RAPD) technique for characterization and assessment of genetic relationships was investigated in nineteen walnut (Juglans regia L.) genotypes used as parents or released as cultivars from the breeding program of the University of California at Davis. Most of the 72 decamer primers used yielded scorable amplification patterns based on discernable bands. The results obtained produced a unique fingerprint for each of the walnut genotypes studied. Cluster analysis separated the 19 walnut genotypes into two main groups whose differences were related to their pedigree. Genotypes sharing common parents tend to group together and with at least one of the parents. Thus, RAPD markers can detect enough polymorphism to differentiate among walnut genotypes, even among closely related genotypes, and the genetic similarity based on RAPDs appears to reflect the known pedigree information. RAPD technology can be useful in current walnut breeding programs, allowing the identification of new cultivars as well as the assessment of the genetic similarity among genotypes which will help in selecting the best parents to obtain new genetic combinations. This revised version was published online in July 2006 with corrections to the Cover Date.     

Characterization of Triticum aestivum/Psathyrostachys juncea derivatives by genomic in situ hybridization

Using the genomic in situ hybridization (GISH) technique, one translocation line, seven translocation-addition lines, five translocation plus translocation addition lines and two ditelosomic addition lines were identified in backcross progenies of Triticum aestivum L. -Psathyrostachys juncea (Fisch.) Nevski intergeneric hybrids. No complete P. juncea chromosomes were detected in the 25 lines studied. The results suggest that intact P. juncea chromosomes may be difficult to isolate in a wheat background. This revised version was published online in July 2006 with corrections to the Cover Date.     

The development of a recombinant Babesia vaccine.

Crude extracts of Babesia bovis parasites were shown to induce levels of protection in susceptible cattle equivalent to that resulting from natural infection. The crude material was systematically fractionated and tested in numerous sequential vaccination/challenge experiments in adult cattle. Antigens in protective fractions were then purified by affinity chromatography with monoclonal antibodies. Three highly protective (more than 95% reduction in parasitaemias) antigens were thus identified. None of these antigens was immunodominant; a number of immunodominant antigens were identified and all were immunosuppressive and/or non-protective. The three protective antigens were cloned and expressed as either beta-galactosidase or glutathione-S-transferase (GST) fusion proteins. Two of these, GST-12D3 and GST-11C5, when used in combination were almost as protective as has been previously shown for the commercially available live attenuated vaccine. A short fragment of a third antigen (21B4) has also been shown to be protective. In two of the antigens, repetitive segments have been shown to be non-protective while the third antigen (12D3) does not contain repetitive domains. Homologues of these antigens exist in other Babesia species and it is anticipated that these may be candidate antigens for protective vaccines against those species.     

Somatostatin: hypothalamic inhibitor of the endocrine pancreas

Somatostatin, a hypothalamic peptide that inhibits the secretion of pituitary growth hormone, inhibits basal insulin secretion in fasted cats and rats. In fasted baboons both basal and arginine-stimulated secretion of insulin and glucagon are inhibited. Somatostatin appears to act directly on the endocrine pancreas. The action is dose-related, rapid in onset, and readily reversed.