Scholarship & Research
Permanent URI for this communityhttps://scholarworks.montana.edu/handle/1/1
Browse
2 results
Search Results
Item Molecular taxonomy, bionomics and host specificity of Longitarsus jacobaeae (Waterhouse) (Coleoptera: Chrysomelidae) : the Swiss population revisited(Montana State University - Bozeman, College of Agriculture, 2003) Puliafico, Kenneth Patrick; Chairperson, Graduate Committee: Jeffrey L. Littlefield.The ragwort flea beetle, Longitarsus jacobaeae (Waterhouse) (Coleoptera: Chrysomelidae) is considered to be the most important biological control agent for the suppression of tansy ragwort, Senecio jacobaea L. (Asteraceae) in the Pacific Northwest. A recent infestation of tansy ragwort in northwest Montana has rekindled the search for a cold adapted strain of the ragwort flea beetle. This study endeavored to determine the molecular taxonomy, host specificity, bionomics and life history of the Swiss strain. I found that populations of L jacobaeae from Switzerland are phenologically adapted to cold continental climates. Molecular techniques of species determination were applied to L. jacobaeae and three other species in the genus Longitarsus. Application of these techniques were able to discriminate between L. jacobaeae and its cryptic sister species L. flavicornis (Stephens). Five Swiss flea beetle populations and three Oregon populations were determined to be clustered together in the L. jacobaeae species. This is the first report of life history observations for naturally occurring populations of L. jacobaeae in Switzerland. Adult flea beetles emerge in early spring and immediately start oviposition by mid-July. Oviposition continued into November for captive beetles. Eggs enter a diapause phase and hatch in the spring after exposure to cold temperatures. Larvae initially feed in the leaves and then move to the root crowns in their second instar to complete their development. Pupation occurs in the soil after the third instar leaves the plant. Twelve plant species closely related to S. jacobaea were exposed to ragwort flea beetles in three host tests. In all three host tests, larval development was completed only in the usual host plant, S. jacobaea. Limited larval feeding was observed in the cut foliage host test on three non-target species, S. eremophilus, S. flaccidus, and S. triangularis, however all the larvae tested died during development. Very slight damage to no-target plants was observed in host tests utilizing whole potted plants in the greenhouse. An. open field host test in Switzerland revealed no substantial attack on non-target plants and no larval development. Eight previously untested North American plant species were found unacceptable hosts to L jacobaeae.Item Systemic resistance induction by Bacillus mycoides isolate Bac J : the mode of action on Beta vulgaris (sugar beet)(Montana State University - Bozeman, College of Agriculture, 2003) Bargabus, Rebecca Lynn; Chairperson, Graduate Committee: John E. Sherwood.Bacillus mycoides isolate Bac J, a non-pathogenic, phyllosphere-inhabiting biological control agent, reduced Cercospora leaf spot of sugar beet by 60-80% in glasshouse experiments, even when spatially separated from the causal agent, Cercospora beticola Sacc. Disease control was attributed to the ability of the bacterium to induce systemic resistance in the host, which was demonstrated through classical induced resistance challenge assays. Additionally, in glasshouse and field experiments three pathogenesis-related proteins, chitinase, beta-glucanase and peroxidase, that are accepted molecular markers of systemic induced resistance, were increased by nearly 2-fold in distal, untreated sugar beet leaves following treatment with Bacillus mycoides isolate Bac J and acibenzolar-S-methyl, a chemical inducer of systemic resistance. The increased activity in all cases was a result of the production of unique isoforms of the enzymes not found in the water treated control. The Bacillus mycoides isolate Bac J-induced systemic defense response was preceded by a biphasic oxidative burst. The hydrogen peroxide production pattern was similar in timing, but not intensity to that elicited by avirulent bacterial pathogens of sugar beet, Erwinia carotovora pv. betavasculorum isolates 1 and 6. Although normally coupled with programmed cell death, the oxidative burst elicited by Bacillus mycoides isolate Bac J was independent of the hypersensitive response. Observations made during the oxidative burst experiments provided keys for understanding the signaling in Bacillus mycoides isolate Bac J-sugar beet interactions, including signal delivery not being reliant upon stomatal conductance and sugar beet receptor location being cytosolic or plasma membrane bound. Additionally, the biochemical and oxidative changes observed in sugar beet following Bacillus mycoides isolate Bac J treatment were consistent with changes seen in other Bacilli-sugar beet interactions in which systemic resistance was induced. These chemical consistencies provided a framework with which to establish a host response-based high throughput screen for the systematic identification of novel, putative Bacilli biological control agents, the first such method of its kind.