蛹虫草病原真菌虫草生齿梗孢Calcarisporium cordycipiticola的生物学特性研究

蛹虫草已经成为我国乃至东南亚地区极其重要的食药用真菌,虽然其子实体已经实现规模化生产,但在产业发展中遇到许多问题,真菌病害为其中之一,如引起蛹虫草“白毛病”病害的虫草生齿梗孢Calcarisporium cordycipiticola。本研究以虫草生齿梗孢为对象,研究了其生物学特性、发病特性及侵染特点。结果表明：该病原菌菌丝分枝较多,短时间内产生大量分生孢子;最适生长温度为25℃,此温度有利于该病害快速传播;其分生孢子比蛹虫草分生孢子耐紫外能力强。栽培过程中该病害多发生在蛹虫草生长发育后期,可以侵染培养基表面、子实体底部、中部和顶端等各个部位。人工接种发现该病原菌可以侵染蛹虫草生长发育的任意阶段,后期子实体被白毛覆盖。对峙实验发现虫草生齿梗孢菌丝逐渐生长到蛹虫草菌丝上,但未发现两菌丝互相缠绕的现象。对该病原菌基本生物学研究,将为建立该病害的早期检测及预防方法提供依据。     

Interaction between Neoaplectana carpocapsae (Nematoda: Steinernematidae) and Apanteles militaris (Hymenoptera: Bracondiae), a parasitoid of the armyworm, Pseudaletia unipuncta

The DD-136 strain of Neoaplectana carpocapsae adversely affected the development of immature stages of Apanteles militaris, a gregarious internal parasitoid of the armyworm, Pseudaletia unipuncta. The adverse effect of the nematode-bacterium complex was indirect, i.e., the infection by the nematode killed the host before A. militaris could complete its development. However, if armyworms containing 10- or 11-day-old A. militaris were exposed to dauer juveniles in Petri dishes, 48.1 and 94.4%, respectively, produced normal cocoons. If hosts containing 9- or 10-day-old A. militaris were fed dauer juveniles, 42.6 and 73.4% of the armyworms, respectively, produced A. militaris which formed normal cocoons. Cocoon-spinning A. militaris larvae were infected by the nematode. After cocoon formation was completed, the dauer juveniles could not penetrate the cocoon and infect the pupa. However, pupae in cocoons which had been deliberately cut open at one end became infected. A. militaris adults were infected when exposed to dauer juveniles in Petri dishes. After 3 days of exposure to dauer juveniles, 25.0, 44.2, and 7.0% of the adults in three trials were alive, whereas 100, 100, and 96.7% of the control adults were alive. Examination of dead adults in the nematode treatment showed that 67.6% contained nematodes. N. carpocapsae developed and reproduced in unparasitized armyworms, in armyworms containing 9-day-old A. militaris, and in those from which A. militaris had emerged. Production of dauer juveniles was significantly higher in unparasitized armyworms and in armyworms containing 9-day-old A. militaris than in those from which A. militaris had emerged.     

Inactivation of Paecilomyces fumosoroseus conidia by diffuse and total solar radiation

Abstract: The detrimental photic effects of natural solar radiation on the conidial persistence of the entomopathogenic hyphomycete Paecilomyces fumosoroseus were investigated by exposing quiescent conidia either to total solar radiation or to its diffuse component. A given amount of UVB diffuse radiation was found to be as detrimental, and sometimes twice as detrimental, as the same amount of total solar radiation. The variability in quantity and spectral distribution of the diffuse component of UVB solar radiation reaching the earth's surface, observed through spectral measurements, may be responsible for the difference in biological effects.     

Adult polyphagous coleopterans overwintering in cereal boundaries: winter mortality and susceptibility to the entomopathogenic fungus Beauveria bassiana

Autumn-collected Bembidion lampros and Agonum dorsale were kept outdoors under semi field conditions to determine winter mortality. On three occasions (autumn, mid-winter and late winter) sub-samples of the population were incubated in the laboratory at room temperature and mortality was recorded. Generally the mortality was low in autumn and mid-winter, not exceeding 5%. A more pronounced post-winter mortality of up to 30% was observed at the end of hibernation. Only a negligible number were infected by the entomopathogenic fungi Beauveria bassiana and Paecilomyces farinosus. Infection experiments with B. bassiana isolates from Sitona lineatus, Tachyporus hypnorum and three species of ground beetles showed a similarly low susceptibility of B. lampros and A. dorsale to B. bassiana and, although Tachyporus spp. showed a distinct mycophagy and a significantly higher mortality, this could not be related to mycosis.     

Antifungal and antitumor activity of heterocyclic thiosemicarbazones and their metal complexes: current status

More than 75 substituted thiosemicarbazones and a number of metal complexes of each have been assayed for their antifungal activity. Their activity is significantly affected by the substituted groups attached at both¹ N and⁴ N of the thiosemicarbazone moiety. Greatest activity occurs for 2-substituted pyridine thiosemicarbazones with differences observed for 2-formylpyridine, 2-acetylpyridine and 2-benzoylpyridine derivatives and their metal complexes. Further, there are activity differences for⁴ N-alkyl-,⁴ N-aryl-,⁴ N-dialkyl- and 3-azacyclothiosemicarbazones and their metal complexes as well as changes in the substituent size among each of these subgroups. Cu(II) complexes are often more active than the uncomplexed thiosemicarbazones, with the latter showing similar activity to Ni(II) complexes in many instances. The reduction potential of the thiosemicarbazone ligand in a Cu(II) complex, the strength of the ligand field and various spectral properties can be correlated to the inhibitory activity.     

Ovicidal and Larvicidal Activity of Conidia and Blastospores of Paecilomyces fumosoroseus (Deuteromycotina: Hyphomycetes) Against Bemisia argentifolii (Homoptera: Aleyrodidae) with a Description of a Bioassay System Allowing Prolonged Survival of Control Insects

Fungi are the only effective entomopathogens of members of the Aleyrodidae and other homopterans because of the piercing and sucking feeding strategy of these insects. The laboratory assessment of the entomopathogenic activity of fungi often requires a prolonged period of observation. Leaf quality can be the limiting factor in bioassays of fungi against whiteflies that require longer observation periods or those that require conditions that are as close to natural ones as possible. A bioassay system is described that utilizes rooted cabbage leaves infested with the highly polyphagous whitefly, Bemisia argentifolii . Using this method, discriminating dosages of aerial conidia and blastospores of two isolates of Paecilomyces fumosoroseus (Pfr) were bioassayed against eggs and nymphs of B. argentifolii . Low, but significant, mortality (10-20%) of eggs was observed 14 days after exposure to 3.8 104 blastospores/cm2 for the Pfr 97 and European Biological Control Laboratory (EBCL) Pfr 42 isolates. Additionally, the majority of crawlers that had hatched from treated eggs died on the surface of the leaves. Exposure of early second-instar nymphs of B. argentifolii to 3.8 103 conidia or blastospores/cm2 of Pfr 97 resulted in mortalities of 27 and 77% respectively. Identical dosages of conidia and blastospores of the Pfr 42 isolate resulted in mortalities of 59 and 68% respectively. The bioassay method described enables the comparative evaluation of entomopathogenic fungi against whiteflies under diverse biotic and abiotic conditions.