超氧化物歧化酶模拟化合物的生物活性研究

根据天然超氧化物歧化酶(SOD)活性部位结构合成了含苯并咪唑的5种配体及其32种分别含Cu（Ⅱ）、Fe（Ⅲ）、Mn（Ⅱ）、Co（Ⅱ）的模拟化合物.经光谱、电化学测试证明这些化合物具有拟S3D活性,其50％抑制率浓度（IC50）为10-6～10-8mol·L-1,催化超氧离子自由基（O-·2）歧化的反应速率常数kq为106～108mol-1·L·s-1.同时观察到几种模拟化合物有抗肿瘤活性或增强水稻抗寒性.     

Biological Parameters for Four Coccinellid Species in Central Saudi Arabia

Developmental and reproductive rates ofAdonia variegataGoeze,Coccinella novemnotataHerbst,C. septempunctataL., andC. undecimpunctataL. were studied in wheat and barley in Central Saudi Arabia. Beetles were reared in the laboratory at 25 ± 2°C onBrevicoryne brassicae(L.) andRhopalosiphum padiL.A. variegataandC. undecimpunctatahad significantly higher egg hatching (X = 81.8 and 74.5%), adult longevity (X = 71.8 and 70.0 days), and survival (X = 61.8 and 61.5%), respectively.Coccinella undecimpunctatahad the highest fecundity (X = 370.5 eggs/female) and longest oviposition period (X = 29.8 days).C. septempunctataexhibited the lowest values for these biological parameters. No differences were evident in the total developmental time or egg and pupal duration, although species differences occurred in the larval duration. Larvae ofA. variegatadeveloped faster (X = 11.8 days) than Larvae ofC. septempunctata(X = 12.0 days),C. undecimpunctata(X = 12.2 days), orC. novemnotata(X = 13.1 days). The intrinsic rate of increase (r_m) and predicted population density were higher forC. undecimpunctata(X = 0.093 and 98553) after 60 days than forC. novemnotata(X = 0.088 and 59405),C. septempunctata(X = 0.086 and 35033), orA. variegata(X = 0.082 and 37991), respectively.     

Natural Occurrence ofChondrostereum purpureumin Relation to Its Use as a Biological Control Agent in Canadian Forests

The incidence of natural fructification ofChondrostereum purpureumwas estimated quantitatively on southern Vancouver Island during two winter seasons in randomly located 1000-m²plots and compared with potential added fructification that might occur as a result of using the fungus to control stump-sprouting of hardwood weeds in young forest stands. Fructification was surveyed in forests as well as in urban or agricultural areas by estimating the surface areas of woody substrates covered with basidiocarps. In addition to random plots, estimates were made also in locations where the fungus would be expected to occur (woodpiles, silvicultural thinnings, and killed trees). Basidiocarps were found throughout the area in various types of forest cover as well as in urban or agricultural situations. The amount of added fructification through the use of the fungus as a biological control agent was determined from inoculated plots as well as from calculated stump-surface areas developed from published stand-density data. Added fructification was multiplied by a factor representing the maximum biological control frequency in order to compare added fructification with natural fructification values. From the various calculations, it was determined that the added fructification ofC. purpureumis of the same order of magnitude as naturally occurring levels or even lower. In addition, there is a distinct geographical separation between predominantly forestry and predominantly settled areas where fruit and ornamental trees are cultivated. Accordingly, it was concluded that using the fungus as a biological control agent in forestry is not likely to pose a significant threat to fruit growing and commercial forests.     

Seasonality ofOrmia depletaand Limits to Its Spread

Ormia depleta(Wiedemann) (Diptera: Tachinidae), a South American fly that homes on the calling songs of its hosts, was brought from Piracicaba, Brazil; colonized; and released in Florida for the biological control ofScapteriscusspp. mole crickets. It became established at some release sites and rapidly spread through most of peninsular Florida. The seasonal distributions of phonotactic females in Florida differed from the single summer peak recorded at Rio Claro and Piracicaba, Brazil (23° S). Near Bradenton (27° N), spring and fall peaks with a summer hiatus were quickly established and remain evident. At two sites near Gainesville (30° N), a strong fall peak and a modest-to-none spring peak developed. Peaks of phonotactic females seem to follow times of peak host availability and sometimes coincide with minima of host availability. Limits to geographical expansion ofO. depletaare poorly understood. At Gainesville, the site of earliest introduction, establishment was rapid and soundtrap catches increased for the first 3 years, exceeding 1000 per year at one site. Catches then declined for 3 years, almost reaching zero in 1994. On the other hand, annual sound-trap catches ofO. depletaat Bradenton exceeded 1000 in <2 years and have remained above that level for 5 years. Winters in Gainesville are more severe than those in Bradenton, but minimum winter temperatures in Gainesville were substantially lower duringO. depleta's increase than during its decline. Perhaps mild winters cause the flies to become active early—only to starve for lack of adequate winter nectar sources.O. depletamay yet spread to the northern limits of itsScapteriscushosts as present populations adapt to new environments. Or farther spread may require that new strains be introduced from more southerly sites in South America.     

CROSSING EXPERIMENTS,LIPID COMPOSITION,AND THE SPECIES CONCEPT IN ECTOCARPUS SILICULOSUS AND E. FASCICULATUS (PHAEOPHYCEAE,ECTOCARPALES)1

Sporophytes of Ectocarpus siliculosus (Dillwyn) Lyngbye and E. fasciculatus Harvey were collected in the vicinity of Roscoff Brittany, France. Gametophytes derived from meiospores were used for intra- and interspecific crosses. Intraspecific gamete combinations gave viable zygotes, which developed into fertile sporophytes. Interspecific crosses were unsuccessful. Gamete fusions did not occur between female gametes of E. fasciculatus and male gametes of E. siliculosus. Hybrid zygotes were formed in the reciprocal combination but died soon after germination. We conclude that the two species of Ectocarpus at Roscoff represent distinct taxonomic entities, which are separated by pre- and postzygotic compatibility barriers. These biological findings are confirmed by the differential occurrence of the chemotaxonomic marker betaine-lipid diacetylglycerylhydroxymethyltrimethyl-β-alanine, which is present in our cultures of E. fasciculatus but absent in E. siliculosus.     

Refuge evolution and the population dynamics of coupled host—parasitoid associations

Summary We have investigated the theoretical consequences of character evolution for the population dynamics of a host—parasitoid interaction, assuming a monophagous parasitoid. In the purely ecological model it is assumed that hosts can escape parasitism by being in absolute refuges. A striking property of this model is a threshold effect in control of the host by the parasitoid, when host density dependence is weak. The approximate criteria for the parasitoid to regulate the host to low densities are (1) that the parasitoid's maximum population growth rate should exceed the host's and (2) that the maximum growth rate of the host in the refuge should be less than unity. We then use this ecological framework as a basis for a model which considers evolutionary changes in quantitative characters influencing the size of the absolute refuge. For each species, an increase in its refuge-determining character comes at a cost to maximum population growth rate. We show that refuge evolution can substantially alter the population dynamics of the purely ecological model, resulting in a number of emergent and sometimes counter-intuitive properties. In general, when the host has a high carrying capacity, systems are polarized either with low or minor refuge and top-down control of the host by the parasitoid or with a refuge and bottom-up control of the host by a combination of its own density dependence and the parasitoid. A particularly tantalizing result is that co-evolutionary dynamics can modify ecologically unstable systems into ones which are either stable or quasi-stable (with bouts of unstable dynamics, punctuating long-term periods of quasi-stable behaviour). We present five quantitative criteria which must all be met for the parasitoid to be the agent responsible for control of the host at a co-evolutionary equilibrium. The apparent stringency of this full set of requirements supports the empirically-based suggestion that monophagous parasitoid-driven systems should be less common in nature than those driven by multiple forms of density dependence. Further, we apply our theory to the question of whether exploiters may harvest their victims at maximum sustainable yields and to the evolutionary stability of biological control. Finally, we present a series of testable predictions of our theory and methods useful for testing them.     

Effects of a Mutant Strain and a Wild Type Strain of Verticillium lecanii on Heterodera glycines Populations in the Greenhouse

A wild type strain ofVerticillium lecanii and a mutant strain with increased tolerance to the fungicide benomyl were evaluated in greenhouse experiments for effects on Heterodera glycines populations. Nematodes were applied at 300 eggs and juveniles per 4,550-cm³ pot (two soybean plants in 4,990 g loamy sand per pot) and at both 300 and 10,000 eggs and juveniles per 1,720-cm³ pot (one soybean plant in 2,060 g sand per pot). With 300 nematodes added per pot, both V. lecanii strains significantly reduced nematode populations in loamy sand (fungus applied at 0.02% dry weight per dry weight loamy sand) and sand (0.006% and 0.06% fungus application rates). The mutant strain applied at 0.002% to sand also significantly reduced cyst numbers. When 10,000 nematodes were added per pot, only the mutant strain at 0.06% significantly decreased population. Various media were tested for isolation of the fungus strains from prills, loamy sand, and sand, but the fungi were recovered from few of the greenhouse pots.     

Selection for non-diapause inAmblyseius cucumeris andAmblyseius barkeri and exploration of the effectiveness of selected strains for thrips control

In Europe and North America the western flower thrips,Frankliniella occidentalis, is an important pest in various greenhouse crops, such as sweet pepper and cucumber. Two species of predatory mite are commercially applied for biological control of this pest:Amblyseius cucumeris andA. barkeri. Thrips control is generally successful from March onwards. During winter, however, thrips control by these predatory mites is less effective. An important reason for this is that the commercially applied strains of both mite species enter reproductive diapause under short-day photoperiods, whereas the western flower thrips does not enter diapause. In this paper we report on selection experiments for non-diapause in strains of both mite species, aimed at obtaining predators that do not enter diapause under light- and temperature conditions prevailing in winter. Additional experiments were done to estimate the potential of the selected lines as control agents ofF. occidentalis. Selection for non-diapause proved highly successful in both predatory mite species. In a New Zealand strain ofA. cucumeris diapause incidence decreased from 41% to 0% in about ten generations; in a Dutch strain ofA. barkeri diapause incidence decreased from 67% to 0% in about six generations. Furthermore, selection for non-diapause had no influence on predator performance, measured as predation rate and oviposition rate on a diet of first instar thirps larvae. Rates of predation and oviposition were the same for selected and unselected lines in both species; rates of predation and oviposition were higher forA. cucumeris than forA. barkeri. After 18 months under non-diapause conditions, no less than 92% of a sample of the selected non-diapause line ofA. cucumeris did not enter diapause when tested under diapause-inducing conditions. This indicates that ‘non-diapause’ is a stable trait in these predatory mites. Finally, a small-scale greenhouse experiment in a sweet pepper crop showed that the selected non-diapause line ofA. cucumeris established successfully under diapause-inducing short-day conditions.     

Life history ofAphis gossypii on cucumber: influence of temperature, host plant and parasitism

Life table data forAphis gossypii Glover (Homoptera: Aphididae), an important pest in glasshouse cucumber crops, were studied at 20, 25 and 30°C on two cucumber cultivars (Cucumis sativus L.) in controlled climate cabinets. The development time on the cucumber cv. ‘Sporu’ ranged from 4.8 days at 20°C to 3.2 days at 30°C. Immature mortality was approximately 20% and did not differ between temperatures. Most mortality occurred during the first instar. Reproduction periods did not differ among temperatures, but at 25 and 30°C more nymphs were produced (65.9 and 69.8 nymphs/♀, respectively) than at 20°C (59,9 nymphs/♀) because of a higher daily reproduction. Intrinsic rate of increase was greatest at 25°C (r _m =0.556 day⁻¹). At 20 and 30°C the intrinsic rate of increase was 0.426 and 0.510, respectively. On cv. ‘Aramon’, the development time ofA. gossypii was approximately 20% longer at all temperatures. Immature mortality did not differ between the two cultivars. The intrinsic rate of increase on cv. ‘Aramon’ was 15% smaller than on cv. ‘Sporu’. The use of cucumber cultivars partially resistant to aphids is discussed in relation to biological control of cotton aphid in glasshouses. Development time and immature mortality on leaves of the middle and upper leaf layer of glasshouse grown cucumber plants (cv. ‘Aramon’) were comparable to development in the controlled climate cabinets. On the lower leaves immature mortality was much higher (approximately 82%) than on leaves of the middle (24.0%) and upper leaf layer (24.5%). Reproduction was less on the lower leaf layer (45.9, 70.5 and 70.1 nymphs/♀ on leaves of the lower, middle and upper leaf layer, respectively). Aphids, successfully parasitized byAphidius colemani Viereck (Hymenoptera: Braconidae) only reproduced when they were parasitized after the third instar. Fecundity was 0.1 to 0.9 and 10.5 to 13.3 nymphs/♀ for aphids parasitized in the fourth instar or as adults, respectively. Reproduction of aphids that were stung but survived the attack was lower than for aphids not stung. Average longevity of these aphids was equal to the longevity of aphids not stung byA. colemani.     

Factors affecting entomopathogenic nematode infection ofPlutella xylostella on a leaf surface

We investigated the ability of entomopathogenic nematodes to infect diamondback moth (DBM),Plutella xylostella (L.) (Lepidoptera: Plutellidae) on a leaf surface. In a leaf disk assay, mortality of late stage DBM larvae ranged from <7% caused bySteinernema kushidai Mamiya to >95% caused byS. carpocapsae (Weiser) All strain. LC₅₀ values forS. carpocapsae, S. riobravis Cabanillas, Poinar & Raulston, andHeterorhabditis bacteriophora Poinar NC1 strain were 14.6, 15.4, and 65.4 nematodes/larva, respectively.S. carpocapsae, S. riobravis, andH. bacteriophora caused 29%, 33%, and 14% mortality of DBM pupae, respectively. DBM mortality caused byS. carpocapsae on radish declined at low (<76%) to moderate (76–90%) RH, because nematode survival and infectivity declined at low (<76%) to moderate (76–90%) RH. However, DBM mortality caused byS. riobravis did not decline with RH.S. riobravis survival declined with RH, but infectivity did not. Overall, nematode survival and infectivity to DBM larvae were lower forS. riobravis than forS. carpocapsae. In addition, DBM mortality was higher on radish plants (pubescent leaves) than on cabbage plants (glaborous leaves).