A simple sustained release device for the ethylene binding inhibitor 1-methylcyclopropene

The efficacy of 1-methylcyclopropene (1-MCP) gas to prevent the adverse effects of ethylene is limited by its short-term residual activity in some plants. Development of a simple 1-MCP sustained release device that prolongs 1-MCP exposure is reported herein. Sustained release devices comprised of polyvinylchloride tubes containing 0.1 g SmartFresh(TM) powder (a.i. 3.3% 1-MCP) and 1.25 ml deionised water were used to release 1-MCP into fibreboard cartons containing cut Geraldton waxflower (Chamelaucium uncinatum Schauer) cv. CWA Pink bunches during export shipment by air (107 h) from Australia to the UK. The devices protected flowers against abscission induced by subsequent test exposures to ethylene (1011,mul l(-1), 12 h, 20 degreesC) for 3-5 days after arrival. In contrast, pre-shipment treatments with either a single application of 790 nl l(-1) 1-MCP for 14 h at 2 degreesC or a 0.2 mM Ag+ (as silver thiosulphate; STS) pulse for 14 h at 2 degreesC protected flowers against exogenous ethylene for only 1-2 days of post-export life. However, pre-shipment 1-MCP fumigation was up to about three-fold more effective than either sustained 1-MCP release or pre-shipment STS treatments in reducing floral organ and leaf abscission from bunches during export. Thus, it is suggested that a combination of pre-shipment 1-MCP fumigation before export with sustained 1-MCP release during shipment should maximise efficacy against ethylene-induced waxflower flower abscission. (C) 2004 Elsevier B. V. All rights reserved.

Genetic diversity among community methicillin-resistant Staphylococcus aureus strains causing outpatient infections in Australia

Increasing reports of the appearance of novel nonmultiresistant methicillin-resistant Staphylococcus aureus MRSA (MRSA) strains in the community and of the spread of hospital MRSA strains into the community are cause for public health concern. We conducted two national surveys of unique isolates of S. aureus from clinical specimens collected from nonhospitalized patients commencing in 2000 and 2002, respectively. A total of 11.7% of 2,498 isolates from 2000 and 15.4% of 2,486 isolates from 2002 were MRSA. Approximately 54% of the MRSA isolates were nonmultiresistant (resistant to less than three of nine antibiotics) in both surveys. The majority of multiresistant MRSA isolates in both surveys belonged to two strains (strains AUS-2 and AUS-3), as determined by pulsed-field gel electrophoresis (PFGE) and resistogram typing. The 3 AUS-2 isolates and 10 of the 11 AUS-3 isolates selected for multilocus sequence typing (MLST) and staphylococcal chromosomal cassette mec (SCCmec) analysis were ST239-MRSA-III (where ST is the sequence type) and thus belonged to the same clone as the eastern Australian MRSA strain of the 1980s, which spread internationally. Four predominant clones of novel nonmultiresistant MRSA were identified by PFGE, MLST, and SCCmec analysis: ST22-MRSA-IV (strain EMRSA-15), ST1-MRSA-IV (strain WA-1), ST30-MRSA-IV (strain SWP), and ST93-MRSA-IV (strain Queensland). The last three clones are associated with community acquisition. A total of 14 STs were identified in the surveys, including six unique clones of novel nonmultiresistant MRSA, namely, STs 73, 93, 129, 75, and 80sIv and a new ST. SCCmec types IV and V were present in diverse genetic backgrounds. These findings provide support for the acquisition of SCCmec by multiple lineages of S. aureus. They also confirm that both hospital and community strains of MRSA are now common in nonhospitalized patients throughout Australia.

Coconut (Cocos nucifera) in vitro ecology: Modifications of headspace and medium additives can optimize somatic embryogenesis

Of those explants tested, immature zygotic embryo tissues proved to be the best for initiating callus with potential for somatic embryogenesis. Slicing of this tissue and use of the central sections (near to and including the meristematic tissue) gave the best embryogenic response. Slices that were placed under illumination necrosed more rapidly and to a greater degree than those incubated in the dark. Explant slice necrosis could be prevented or severely retarded by the addition of activated charcoal into the medium. Washing the explants for short periods of time prior to culture was also found to improve callus production. Prolonged washing resulted in low rates of callus production. In an attempt to prevent ethylene accumulation in the culture vessel headspace, AVG, an ethylene biosynthesis inhibitor and STS, a chemical which reduces the physiological action of ethylene, were successfully used to promote somatic embryogenesis. Spermidine, putrescine and spermine, polyamines that are known to delay plant senescence and promote somatic embryogenesis in some plant species, enhanced the rate of somatic embryogenesis when they were introduced into the callus induction medium. The use of polyethylene glycol in combination with abscisic acid helped promote somatic embryo formation and maturation as well as the subsequent formation of plantlets. The use of all of these improvements together has created a new and improved protocol for coconut somatic embryogenesis. This new protocol puts significant emphasis on improving the in vitro ecology of the explant, callus and somatic embryogenic tissues.