Natural enemies of rice leaf folder Cnaphalocrocis medinalis (Guenée) —a critical review

A chronological review of the biological control agents of rice leaf folder, Cnaphafalocrocis medinalis Guenée, including the stage of host attacked in different countries, their activity and suggestions for future. The rice leaf folder, Cnaphalocrocis medinalis Guenée, which was a pest of minor importance till the last decade, recently has assumed major importance in many rice ecosystem of Asia, the South Pacific Islands, Hawaii and Australia (Hirao, 1982). Increasingly frequent outbreaks of this pest (Table I) in recent years have been attributed to the introduction of modern rice technologies, namely: Continuous and overlapping cropping (Rajamma and Das, 1969); introduction of broad leaf dwarf, high tillering. fertilizer responsive susceptible rice varieties (Gargav and Katiyar, 1971; Dorge et al., 1972; Patel, 1975) and increased use of nitrogenous fertilizers (Michael Raj and Morachan, 1973; Chandragiri et al., 1974; Subraiah and Morachan, 1974; Dhaliwal et al., 1979; Chantaraprapha el al., 1980; Miynhara, 1981). In addition shading which causes the rice plants to grow tall with reduced silica content may make plants more susceptible (Chelliah, 1983). However, no detailed information is available as to how these factors bring about favourable conditions for larval growth and survival and or cause enhanced fecundity of the adults

Natural enemies of rice leaf folder Cnaphalocrocis medinalis (Guenée) —a critical review

A chronological review of the biological control agents of rice leaf folder, Cnaphafalocrocis medinalis Guenée, including the stage of host attacked in different countries, their activity and suggestions for future. The rice leaf folder, Cnaphalocrocis medinalis Guenée, which was a pest of minor importance till the last decade, recently has assumed major importance in many rice ecosystem of Asia, the South Pacific Islands, Hawaii and Australia (Hirao, 1982). Increasingly frequent outbreaks of this pest (Table I) in recent years have been attributed to the introduction of modern rice technologies, namely: Continuous and overlapping cropping (Rajamma and Das, 1969); introduction of broad leaf dwarf, high tillering. fertilizer responsive susceptible rice varieties (Gargav and Katiyar, 1971; Dorge et al., 1972; Patel, 1975) and increased use of nitrogenous fertilizers (Michael Raj and Morachan, 1973; Chandragiri et al., 1974; Subraiah and Morachan, 1974; Dhaliwal et al., 1979; Chantaraprapha el al., 1980; Miynhara, 1981). In addition shading which causes the rice plants to grow tall with reduced silica content may make plants more susceptible (Chelliah, 1983). However, no detailed information is available as to how these factors bring about favourable conditions for larval growth and survival and or cause enhanced fecundity of the adults

Structure-activity relationship studies on the macrolide exotoxin mycolactone of Mycobacterium ulcerans

BACKGROUND: Mycolactones are a family of polyketide-derived macrolide exotoxins produced by Mycobacterium ulcerans, the causative agent of the chronic necrotizing skin disease Buruli ulcer. The toxin is synthesized by polyketide synthases encoded by the virulence plasmid pMUM. The apoptotic, necrotic and immunosuppressive properties of mycolactones play a central role in the pathogenesis of M. ulcerans. METHODOLOGYPRINCIPAL FINDINGS: We have synthesized and tested a series of mycolactone derivatives to conduct structure-activity relationship studies. Flow cytometry, fluorescence microscopy and Alamar Blue-based metabolic assays were used to assess activities of mycolactones on the murine L929 fibroblast cell line. Modifications of the C-linked upper side chain (comprising C12-C20) caused less pronounced changes in cytotoxicity than modifications in the lower C5-O-linked polyunsaturated acyl side chain. A derivative with a truncated lower side chain was unique in having strong inhibitory effects on fibroblast metabolism and cell proliferation at non-cytotoxic concentrations. We also tested whether mycolactones have antimicrobial activity and found no activity against representatives of Gram-positive (Streptococcus pneumoniae) or Gram-negative bacteria (Neisseria meningitis and Escherichia coli), the fungus Saccharomyces cerevisae or the amoeba Dictyostelium discoideum. CONCLUSION: Highly defined synthetic compounds allowed to unambiguously compare biological activities of mycolactones expressed by different M. ulcerans lineages and may help identifying target structures and triggering pathways

DESIGN OF THE SPEAR 3 LIGHT SOURCE †

The venerable SPEAR storage ring will be replaced in 2003 with a modern, low emittance 3 GeV ring optimized for producing high flux and high brightness photon beams at the Stanford Synchrotron Radiation Laboratory. SPEAR 3 will have an emittance of 18 nmrad, reduced from 160 nm-rad, and a 500-mA beam current, increased from 100 mA. A water-cooled copper vacuum chamber will be thermally stable and, together with mode-damped RF cavities, will assure multibunch beam stability. Beam lines will see one to two orders of magnitude increase in beam flux density and brightness after they have been upgraded for the higher beam power. A 6-month ring installation is planned to minimize the impact on the SSRL user program. SPEAR 3 accelerator design and beam properties are reviewed.