Pyrethrins Protect Pyrethrum Leaves Against Attack by Western Flower Thrips, Frankliniella occidentalis

Pyrethrins are active ingredients extracted from pyrethrum flowers (Tanacetum cinerariifolium), and are the most widely used botanical insecticide. However, several thrips species are commonly found on pyrethrum flowers in the field, and are the dominant insects found inside the flowers. Up to 80 % of western flower thrips (WFT, Frankliniella occidentalis) adults died within 3 days of initiating feeding on leaves of pyrethrum, leading us to evaluate the role of pyrethrins in the defense of pyrethrum leaves against WFT. The effects of pyrethrins on WFT survival, feeding behavior, and reproduction were measured both in vitro and in planta (infiltrated leaves). The lethal concentration value (LC50) for pyrethrins against WFT adults was 12.9 mg/ml, and pyrethrins at 0.1 % (w/v) and 1 % (w/v) had significantly negative effects on feeding, embryo development, and oviposition. About 20-70 % of WFT were killed within 2 days when they were fed chrysanthemum leaves containing 0.01-1 % pyrethrins. Chrysanthemum leaves containing 0.1 % or 1 % pyrethrins were significantly deterrent to WFT. In a no-choice assay, the reproduction of WFT was reduced significantly when the insects were fed leaves containing 0.1 % pyrethrins, and no eggs were found in leaves containing 1 % pyrethrins. Our results suggest that the natural concentrations of pyrethrins in the leaves may be responsible for the observed high mortality of WFT on pyrethrum

Conferred resistance to Botrytis cinerea in Lilium by overexpression of the RCH10 chitinase gene

The production of ornamentals is an important global industry, with Lilium being one of the six major bulb crops in the world. The international trade in ornamentals is in the order of £60-75 billion and is expected to increase worldwide by 2-4 % per annum. The continued success of the floriculture industry depends on the introduction of new species/cultivars with major alterations in key agronomic characteristics, such as resistance to pathogens. Fungal diseases are the cause of reduced yields and marketable quality of cultivated plants, including ornamental species. The fungal pathogen Botrytis causes extreme economic losses to a wide range of crop species, including ornamentals such as Lilium. Agrobacterium-mediated transformation was used to develop Lilium oriental cv. ‘Star Gazer’ plants that ectopically overexpress the Rice Chitinase 10 gene (RCH10), under control of the CaMV35S promoter. Levels of conferred resistance linked to chitinase expression were evaluated by infection with Botrytis cinerea; sporulation was reduced in an in vitro assay and the relative expression of the RCH10 gene was determined by quantitative Reverse-Transcriptase PCR. The extent of resistance to Botrytis, compared to that of the wild type plants, showed a direct correlation with the level of chitinase gene expression. Transgenic plants grown to flowering showed no detrimental phenotypic effects associated with transgene expression. This is the first report of Lilium plants with resistance to Botrytis cinerea generated by a transgenic approach

The influence of relative humidity on disease caused by Botrytis cinerea in non-harvested versus harvested waxflower flowers

Waxflower (Chamelaucium) is an Australian native plant cultivated for cut flowers. The major problem during postharvest handling and transport of cut waxflower stems is floral abscission caused by Botrytis cinerea. To investigate infection of waxflower flowers by this fungal pathogen, experiments were conducted encompassing various environmental conditions in the laboratory, greenhouse and field with two waxflower cvs. Mullering Brook and My Sweet Sixteen. Under laboratory conditions at 20A degrees C and > 95% RH in moistened bags, flowers of both cultivars either harvested or non-harvested showed similar susceptibility to B. cinerea. For inoculated and non-inoculated sprigs at 11 days after treatment, disease incidence on cvs. Mullering Brook and My Sweet Sixteen flowers ranged between 99.0-99.2% and 88.4-88.9%, respectively. Corresponding floral abscission ranges were 98.5-100% and 88.4-92.9%, respectively. Under greenhouse conditions and > 95% RH, floral abscission ranges for inoculated flowers of both cultivars were 69.1-71.1% and 46.0-73.0%, respectively. Corresponding disease incidence ranges were 54.9-55.8% and 28.8-43.4%, respectively. Under field conditions and > 95% RH, cv. My Sweet Sixteen flowers were more resistant to B. cinerea infection (3.0-3.1% in year 1; 0.9-2.0% in year 2) than were cv. Mullering Brook flowers (33.1-51.9% in year 1; 44.0-57.1% in year 2). Under all experimental conditions, inoculated flowers that were not covered with moistened bags showed significantly (P < 0.05) lower levels of disease incidence (0-11.9%) and floral abscission (2.4-37.8%). This observation is consistent with quiescence of the fungus in the field, and activation of infection by favourable temperature and humidity conditions after harvest leading to floral abscission