Assessing Potato Psyllid Haplotypes in Potato Crops in the Pacific Northwestern United States

The potato psyllid, Bactericera cockerelli (?ulc), is a vector of the bacterium ‘Candidatus Liberibacter solanacearum’ (Lso) that has been linked to the economically devastating zebra chip disease of potato. To date, four haplotypes of the potato psyllid have been identified and include Central, Western, Northwestern, and Southwestern haplotypes. Zebra chip was reported in potato crops in the Pacific Northwestern United States for the first time in 2011, and the Lso-infected psyllids collected from zebra chip-affected fields were identified as the Western haplotype. Additional studies have reported a mix of the Western and Northwestern psyllid haplotypes in the Pacific Northwest. The present study further examined psyllid population dynamics over the duration of the 2012 potato season in the Pacific Northwest by haplotype analysis of 864 potato psyllids collected from potato fields in Washington, Oregon, and Idaho. In the Yakima Valley of Washington and the lower Columbia Basin of Washington and Oregon, the Northwestern haplotype was predominant (78 %), and was detected earlier in the season than the Western haplotype. Interestingly, in south-central Idaho, all four psyllid haplotypes were identified, but the predominant haplotype was the Western haplotype (77 %). Here, Northwestern psyllids were detected early in the season from June to mid-August, whereas Central psyllids were detected in late July and thereafter. These results suggest that haplotype composition of psyllid populations in potato fields throughout the 2012 growing season in south-central Idaho differed greatly from those in Washington and Oregon. Additionally, all psyllids were analyzed for the presence of Lso, and no Lso-positive psyllids were found in Washington and Oregon, whereas Lso-positive psyllids were found in south-central Idaho. These Lso-positive psyllids consisted of the Western, Northwestern, and Central haplotypes.     

Haplotypes of the Potato Psyllid, Bactericera cockerelli, on the Wild Host Plant, Solanum dulcamara, in the Pacific Northwestern United States

‘Candidatus Liberibacter solanacearum’ (Lso) is a bacterium that infects solanaceous crops and causes plant decline and yield losses, especially in potato and tomato. Lso is transmitted to these hosts by the potato psyllid (Bactericera cockerelli Sulc) vector. B. cockerelli host plants are not limited to crop plants, but also include many wild, solanaceous weeds. These wild hosts could potentially impact overwintering and breeding of the psyllids and serve as reservoirs for Lso. In the Pacific Northwestern United States, B. cockerelli was recently reported to overwinter on bittersweet nightshade (Solanum dulcamara L.). The present study utilized high resolution melting analysis of the B. cockerelli mitochondrial cytochrome c oxidase I gene to assess the psyllid populations occurring on S. dulcamara during the summer and winter months in Washington, Oregon, and Idaho. This technique has previously been used to analyze the cytochrome c oxidase I gene of B. cockerelli, and has identified four psyllid haplotypes. Lso infection was also determined for the psyllids collected from S. dulcamara. During both the summer and the winter months in the Pacific Northwest, the Northwestern psyllid haplotype was the predominant population found living on S. dulcamara. However, low levels of the Western psyllid population were also present in Washington and Oregon during the same period. No overwintering psyllids tested were Lso-infected, suggesting that these populations do not pose an imminent threat of Lso transmission to newly emerging potatoes and other solanaceous crops in the region, unless a source of Lso becomes available.     

Assessment of herbicides for use on the sweet herb,Stevia rebaudiana in the tropics

SUMMARY

The leaves and stems of Stevia rebaudiana produce steviol glycosides which are sweeter than sucrose, of low calorific value, pH- and heat-stable, and may have a variety of therapeutic benefits. Stevia seed germination is poor and the initial stages of growth are slow, which makes young plants susceptible to competition from weed species. In Australia, no herbicides are currently registered for use on Stevia. The purpose of this study was to assess the efficacy of 16 herbicides on S. rebaudiana and associated weeds. All 16 herbicides were trialled at their most relevant application rates at a field site in tropical Queensland. The best four performers were then tested at two rates of application at another tropical site. The post-planting, pre-weed emergence, oryzalin-containing herbicide, Prolan 500, at either 6.8 or 8.5 l ha^?1 provided the best weed control without affecting the biomass of the Stevia crop. High-performance liquid chromatography was used to determine if rebaudioside A and stevioside concentrations were affected in leaves treated with Prolan 500. It was found that at 1, 4, and 8 weeks after treatment, 8.5 l ha^?1 Prolan 500 resulted in significantly lower rebaudioside A and stevioside concentrations than applying Prolan 500 at 6.8 l ha-1. We therefore recommend that the oryzalin-containing herbicide, Prolan 500 is suitable for use on S. rebaudiana at an application rate of 6.8 l ha^?1.     

A retrospective evaluation of congenital ocular defects in Australian Shepherd dogs in Australia

OBJECTIVE: A retrospective survey of ocular defects in Australian Shepherd dogs was conducted following concerns raised by breeders and owners in Australia. This is the first known such study conducted for this breed. RESULTS: Data from this survey indicate that persistent hyaloid remnants (PHR) were the most common eye defect noted in the Australian Shepherd. Collie eye anomaly (CEA) is the second most common defect noted by veterinary ophthalmologists in the breed in Australia, and extra eyelashes (ectopic cilia/distichia) the third most common. CONCLUSIONS: The data also support the hypothesis that PHR may be inherited in this breed. Further investigation is needed to reveal the status of PHR in this breed.     

Pine somatic embryogenesis: analyses of seed tissue and medium to improve protocol development

The shift from vegetative to embryogenic growth requires tissue to enter a radically different program of development and can be studied in vitro through the development of somatic embryos. From an applied perspective somatic embryogenesis (SE) is expected to play an important role in increasing productivity, sustainability, and uniformity of future forests. For commercial use, SE technology must work with a variety of genetically diverse trees. Since the first reports of SE in Picea abies and Larix decidua in 1985, many different coniferous species have shown the ability to produce embryogenic tissue. However, initiation frequency is often low, many desired seed sources are recalcitrant, and culture survival is often poor, raising costs of somatic seedlings produced from successful genotypes. A number of tools are now available to improve embryogenic tissue initiation and somatic embryo development in vitro that have resulted from analytical studies of seed tissues, the seed environment and gene expression in megagametophyte, zygotic embryos and somatic embryos. Benefits have occurred from medium supplementation with hormones, plant growth regulators, hormone inhibitors and polyamines. Somatic embryo growth has been enhanced with medium supplementation of nutritional components including specific sugar types, vitamins, organic acids, and redox potential modifiers. Control of environmental factors including, water potential, pH, adsorption of medium components by activated carbon and liquid versus gelled medium have also led to SE protocol improvements. The use of analytical studies to duplicate the seed environment in vitro is improving protocol development resulting in increased initiation, improved yields and higher-quality somatic embryos.