A Wilson

Dietary Microbial Toxins and Type 1 Diabetes

Abstract: Toxins may promote type 1 diabetes by modifying or damaging the β cell causing release of autoantigens. Streptomyces is a common soil bacterium that produces many toxic compounds. Some Streptomyces can infect vegetables, raising the possibility of dietary exposure to toxins. We aimed to identify toxins that erode cellular proton gradients in extracts of Streptomyces and infested vegetables and to establish the effect of low doses of these toxins on pancreatic islets in mice. The vacuolar ATPase inhibitors, bafilomycin and concanamycin, and the ionophore, nigericin, were identified in extracts from 4 of 13 Streptomyces isolated from infested potatoes and in potatoes themselves. Injection of bafilomycin A1 into mice impaired glucose tolerance, reduced islet size, and decreased relative β cell mass. Thus, exposure to small quantities of bafilomycin in the diet may contribute to the cause of type 1 diabetes.

Stable and Extreme Resistance to Common Scab of Potato Obtained Through Somatic Cell Selection

Somatic cell selection with thaxtomin A as a positive selection agent was used to isolate variants of potato cv. Russet Burbank with strong to extreme resistance to common scab. Glasshouse and field trials identified 51 variants with significantly reduced disease incidence (frequency of infected tubers) and severity (tuber lesion coverage) compared with the parent cultivar. The most promising variants exhibited extreme disease resistance, rarely showing lesions, which were invariably superficial and shallower than those on the parent. Resistance traits were consistently expressed both in 10 glasshouse and two field trials at different locations, with varied inoculum and disease pressure. Disease-resistant variants differed in their response to thaxtomin A in tuber slice bioassays. Of 23 variants tested, 10 showed reduced thaxtomin A susceptibility, with the remaining 13 responding similar to that of the parent. Thus, toxin tolerance was not the only factor responsible for observed disease resistance; however, four of the five most disease-resistant variants had enhanced thaxtomin A tolerance, suggesting that this factor is important in the expression of strong disease resistance. Pathogenicity and toxin tolerance remained stable over a 6-year period, demonstrating that selected phenotypes were robust and genetic changes stable. The majority of disease-resistant variants had tuber yields equivalent to the parent cultivar in glasshouse trials. This suggests that selection for disease resistance was not associated with negative tuber attributes and that certain variants may have commercial merit, worthy of further agronomic testing.

Receiver Operating Characteristic curve analysis determines association of individual potato foliage volatiles with onion thrips preference, cultivar and plant age

Tomato spotted wilt virus (TSWV) causes sporadic but serious disease in Australian potato crops. TSWV is naturally spread to potato by thrips of which Thrips tabaci is the most important. Prior studies indicated possible non-preference of potato cultivars to T. tabaci. Select potato cultivars were assessed for non-preference to T. tabaci in paired and group choice trials. Cultivars ‘Bismark’, ‘Tasman’ and ‘King Edward’ were less preferred than ‘Atlantic’, ‘Russet Burbank’ and ‘Shepody’. Green leaf volatiles were sampled using solid-phase microextraction from the headspace of potato cultivars of two ages that differed in T. tabaci preference. Analysis of headspace volatile data using Receiver Operating Characteristic curves identified individual volatiles associated with T. tabaci preference and non-preference, young and old plants and individual cultivars. These data could be used to inform breeding programs for selection of T. tabaci resistance to assist with TSWV management, and biological testing of novel thrips management compounds.

Brevipalpus oncidii, a new record for Australia, is not a vector of Orchid fleck virus

ABSTRACT Brevipalpus oncidii Baker was detected for the first time in Australia naturally present as a pest on Brassia verrucosa Bateman ex Lindl. orchids. Although the majority of Brevipalpus species are believed to be predominantly thelytokous, males in the population described in this study were observed to be sexually functional. In repeated transmission studies, this B. oncidii population failed to successfully acquire an isolate of Orchid fleck virus (OFV) and transmit to cymbidium hosts. Mites fed on OFV-infected cymbidium leaves initially tested positive for OFV, but this was lost within 48 hours in absence of the OFV host suggesting failure to internalize the virus within the mite. http://www.zoobank.org/urn:lsid:zoobank.org:pub:1A8E42C2-9A9E-4066-94DC-E9E9683D8C68