害虫防治用玫烟色拟青霉分生孢子粉的干燥工艺优化*

用液—固两相法生产的玫烟色拟青霉Paecilomyces fumosoroseus Pfr116菌株的分生孢子粉,在高真空冷冻干燥、高真空室温抽干、35℃下烘干和低真空低热干燥条件下进行不同程序的干燥处理,以筛选适合该菌孢子粉生产的干燥工艺条件。结果表明,低真空(0.1 MPa)低热(30℃)抽干20~24 h的干燥方法最适合用于该菌孢子粉的干燥,既能保证含水量在9.0%以下,又能保证87%以上的活孢率和1130亿~1310亿/g的含孢量,而且操作简便,成本较低,可作为高纯度孢子粉生产的首选干燥工艺。高真空(15.86 Pa)条件下无论冻干还是室温抽干,虽然孢子粉的含水量(2.2%~8.7%)和含孢量(1270亿~1360亿/g)指标符合生产要求,但活孢率仅62%,说明该菌孢子不适合在高真空条件下干燥。在35℃下烘干24 h所获孢子粉含水量、24 h萌发率和含孢量分别为9.6%、82.8%和1200亿/g,该方法也可在生产中应用,但其活孢率显著低于(P<0.05)低真空低热抽干24 h的孢子粉。     

红火蚁病原真菌AUGM47早期发育超微结构研究

在前期筛选已获得对红火蚁Solenopsis invicta Buren高效致病真菌罗伯茨绿僵菌Metarhizium robertsii AUGM47的基础上,为进一步明确病原真菌对寄主昆虫的侵染机制。本试验在室内条件下,以红火蚁工蚁为侵染对象,利用荧光显微镜和透射电镜观察了罗伯茨绿僵菌AUGM47侵染单元分生孢子在体表附着萌发、穿透和体内增殖的早期发育过程。结果表明,菌株AUGM47分生孢子在红火蚁体表可萌发并形成附着胞侵入,接种后12 h观察到萌发,在36 h内普遍出现穿透结构穿透体壁。接种后48 h为菌体在血腔内的增殖阶段。菌丝体在穿透表皮和体腔内增殖过程中伴随着机械压力和酶的活动。接种后96 h,观察到自噬现象,菌体通过自噬降解并回收细胞器,为从体内穿出的晚期发育过程提供物质基础。本研究对罗伯茨绿僵菌AUGM47分生孢子在红火蚁体外至体内的发育进程研究证实了菌株的高致病性,为红火蚁生防真菌菌种改良和后续开发利用奠定理论基础。     

哈氏木霉分生孢子发育的超微结构和细胞化学

通过电子显微镜和细胞化学标记研究了哈氏木霉分生孢子发育的超微结构和细胞化学。分生孢子发育的超微结构研究表明,分生孢子壁的发育是有个由薄而光滑到厚而有疣的过程;期间脂肪体在分生孢子和产孢细胞中不断累积,最后脂肪体沿着内壁排列成一层。免疫金标记结果显示,幼嫩的分生孢子壁中缺乏几丁质和纤维素,只有在成熟的分生孢子壁中含有几丁质;出乎意料的是在成熟分生孢子中发现有少量纤维素的存在。     

Use of statistical tools in the study of the conditions of predation of Duddingtonia flagrans versus Panagrellus sp

The objective of the present work was to study the conditions of predation of Duddingtonia flagrans conidia versus Panagrellus sp using response surface methodology. Conidia of D. flagrans (AC001) isolate were transferred into water-agar (WA) culture media at different pHs and different concentrations defined according to Central Composite Design (CCD). Five different concentrations of D. flagrans conidia: (1292, 500, 1000, 1500 and 1707) were used. For 2%WA media were used the following pHs were used: 6.29, 6.5, 7.0, 7.5 and 7.71. The response of the design corresponded to the number of larvae (transformed to square root scale) observed at the end of the experiment (10 days). At the tenth day, the non predated larvae were recovered in the Petri dishes. The results showed that 2%WA media at pH 7.0 contributed to improve the predatory activity of conidia of D. flagrans, and therefore this tool may be used in future studies under laboratory and natural conditions.     

Identification of Botrytis spp. on Plants Grown in Iran

A total of 363 isolates were collected from all over Iran. They were isolated from apple, arum lily, briar rose, bride wort, broad bean, camellia, canola, carnation, cucumber, egg plant, feijoa, geranium, gerbera, gladiolus, grape, guilder rose, hibiscus, iris, kiwifruit, oleander, onion, orange, pear, pomegranate, primrose, quince, redbud, robinia, rose, rubber plant, sow thiste, spathe flower, strawberry, tomato, violet, wall flower and wheat. To identify the species, morphological characters such as conidiophore length, conidial and sclerotial dimensions were measured. According to morphological and cultural characters, eight Botrytis species were identified: B. aclada sensu lato, B. cinerea, B. fabae, B. convoluta, B. gladiolorum, B. paeoniae, B. pelargonii and B. porri. As far as we are aware, this is the first report of the last five species from Iran. These species were examined by polymerase chain reaction (PCR) using necrosis and ethylene‐inducing protein (NEP2) and C729 primers. A 835 bp band was amplified in B. cinerea, B. fabae and B. pelargonii, using NEP2, but not in others. However, C729 primers amplified a 700 bp band in B. cinerea and B. pelargonii and a 600 bp in B. fabae.     

Effects of media composition on submerged culture spores of the entomopathogenic fungus, Metarhizium anisopliae var. acridum, Part 1: Comparison of cell wall characteristics and drying stability among three spore types

Metarhizium anisopliae var. acridum (IMI 330189) can produce at least three spore types in vitro; blastospores, submerged conidia, and aerial conidia, as defined by culturing conditions, sporogenesis, and spore morphology. This study compares morphological characteristics (dimensions and cell wall structure), chemical properties of cell wall surfaces (charge, hydrophobicity, and lectin binding), and performance (germination rate and drying stability) among these three spore types. Submerged conidia and aerial conidia both possessed thick, double-layered cell walls, with hydrophobic regions on their surfaces. However, in contrast to aerial conidia, submerged conidia have: (1) a greater affinity for the lectin concanavalin-A; (2) more anionic net surface charge; and (3) a less distinct outer rodlet layer. Blastospores were longer and more variable in length than both submerged conidia and aerial conidia, and had thinner single-layered cell walls that lacked an outer rodlet layer. Also, blastospores had a greater affinity than either conidia type for the lectin, wheat germ agglutinin. Blastaspores lacked hydrophobic regions on their surface, and had a lower anionic net surface charge than submerged conidia. In culture, blastospores germinated the fastest followed by submerged conidia, and then aerial conidia. Survival of submerged conidia and aerial conidia were similar after drying on silica gel, and was greater than that for blastospores. We provide corroborating information for differentiating spore types previously based on method of production, sporogenesis, and appearance of spores. These physical characteristics may have practical application for predicting spore-performance characteristics relevant to production and efficacy of mycoinsecticides.     

Release of the extracellular matrix from conidia ofBlumeria graminis in relation to germination

The release of extracellular matrix (ECM) and the emergence of germ tubes from conidia ofBlumeria graminis were studied by light microscopy and micromanipulation. More prompt and frequent ECM release was confirmed on an artificial hydrophobic substratum than on an artificial hydrophilic substratum. Conidia initially incubated on the hydrophilic substratum were transferred by micromanipulation to either the hydrophobic or the hydrophilic substrata. Immediately after transfer onto the hydrophobic substratum, 75% of conidia released ECM, whereas only 16% did so upon transfer to the hydrophilic substratum. Conidia transferred onto the hydrophobic substratum produced a primary germ tube (PGT) more promptly and frequently than those transferred to the hydrophilic substratum. Thus, conidia recognize and respond to substratum hydrophobicity perhaps immediately after contact. When inoculated onto either isolated barley cuticle or the hydrophobic artificial substratum, 2/3 of the conidia produced a PGT from their polar regions. By contrast, on the hydrophilic substratum 2/3 of conidia did so from the side region. These results show that substratum hydrophobicity affects the location of PGT emergence from conidia. Furthermore, the study indicates that very rapid recognition of surface hydrophobicity by conidia promotes ECM release and this in turn may influence the location of PGT emergence.     

Infection of Sentinel Cotton Aphids (Homoptera: Aphididae) by Aerial Conidia ofNeozygites fresenii(Entomophthorales: Neozygitaceae)

Uninfected adultAphis gossypii(Homoptera: Aphididae) apterae (sentinel aphids) on cotton leaves were exposed for 8 h to the air over a commercial cotton field in Louisiana during the night of 1–2 July 1995. At 0015 h there were 90,437 primary conidia/m³air of the fungusNeozygites fresenii(Entomophthorales: Neozygitaceae) at the midfield position as determined from Rotorod samples. Forty-eight percent (n = 106) of the sentinel aphids exposed for 8 h at midfield were infected by aerial conidia ofN. fresenii.Exposure of sentinel aphids outside the cotton field, at 10 and 100 m downwind and 10 m upwind, resulted in 34.8% (n = 131), 24.0% (n = 129), and 17.4% (n = 146) infected aphids, respectively. These data demonstrate that wind-dispersed aerial conidia ofN. freseniiare infective and rapidly and efficiently disperse the pathogen throughout aphid populations within and between fields.