长枝木霉对南方根结线虫致死和寄生作用的显微观察及测定研究

对不同时期长枝木霉(Trichoderma longibrachiatum)分生孢子悬浮液对南方根结线虫(Meloidogyne incognita)2龄幼虫的致死和寄生作用过程进行了显微观察和室内测定.显微观察结果表明,侵染初期长枝木霉分生孢子吸附或寄生在虫体的表面,并且分生孢子萌发产生大量的菌丝穿透虫体体壁.侵染后期被分生孢子寄生的虫体开始出现畸形,且寄生的部位出现缢缩和溶解,甚至有的虫体完全溶解.室内测定结果表明,不同浓度长枝木霉分生孢子悬浮液对2龄幼虫具有明显的致死和寄生作用,并且不同浓度长枝木霉分生孢子悬浮液之间存在显著的差异.第14天浓度为1.5×107个/mL的长枝木霉分生孢子悬浮液对2龄幼虫的寄生率为87.33％,以及72 h后2龄幼虫的死亡率和校正死亡率分别为90.00％和88.81％.     

柑橘锈皮虫的发生与防治

柑橘锈皮虫又名爆皮虫 ,属鞘翅目、吉丁虫科。以幼虫蛀食主干和主枝。受害部位首先产生流胶现象 ,继而树皮爆裂 ,形成层中断 ,阻碍养分输送 ,引起枝干枯死 ,乃至全株死亡。柑橘锈皮虫 1年发生 1代。以不同虫龄幼虫在树干木质部浅处越冬 ,翌年 3,4月各龄幼虫先后在树干内化蛹 ,5～ 7月成虫羽化出洞 ,先在树冠啃食嫩叶 ,有假死性 ,卵多产在树干的裂缝处 ,6～ 8月为产卵盛期 ,幼虫孵化后 ,危害树皮表面呈芝麻状油渍点 ,随后有泡沫状流胶物质出现。随着幼虫龄期的增加 ,被害部分产生不规则隧道 ,隧道内充满虫粪 ,使树皮和木质部分离枯死而爆裂。…     

进境台湾芹菜上一株变黑轮枝菌的鉴定

从进境台湾芹菜组织中分离出一株菌株F03718,经形态学观察和rDNA ITS序列分析,将该分离物鉴定为变黑轮枝菌(Verticillium nigrescens)。这是首次从我国台湾进境旅客携带物芹菜中检出变黑轮枝菌。     

苹果树腐烂病树皮带菌部位和侵入途径

苹果树腐烂病菌是伤口寄生菌,其菌丝经带有死组织的伤口或经死组织侵入。但在田间,还常见到在没有伤口或死组织的部位也发了病。为此,作者试图通过试验的方法,明确苹腐菌经树皮表面死组织和经叶痕、果柄痕、皮孔侵入,并在其中潜伏的可能性。 病原菌侵入和扩展要求条件不同。苹腐菌侵入后,当侵染点周围组织健康时,一般不能立即扩展致病,而潜伏侵染。此时,往往不易判定菌丝是否已侵入。为此,做了以下三个试验:     

辽宁西部地区苹果树皮含钾量与腐烂病发生关系和矫治效果

在辽西地区国光苹果大树园,完善腐烂病树病情分级标准,适当增加样本数,将生长期叶分枝改为春季发芽前树皮分析,研究发现,树皮中含钾量与腐烂病发生程度之间呈极显著负相关,经初步验证,结果一致,矫治试验结果表明,春季增施钾肥,可提高树皮含钾量并减轻腐烂病发生程度。     

球孢白僵菌自然流行病与马尾松毛虫种群的相互关系

2006年4月下旬发现皖东明光县紫阳林场马尾松毛虫种群中暴发球孢白僵菌自然流行病。根据踏查确定了流行中心区,其僵虫密度远高于周围未流行区域;但中心区僵虫密度不同,最低不到1头／m^2,最高达39头／m^2,形成许多小型流行中心。据此断定,高密度的越冬马尾松毛虫种群呈聚集分布,有利于发病和流行中心的形成。根据僵虫虫龄结构,4～5龄幼虫占僵虫总数93．4％,3龄居中,6龄最少;根据僵虫分布部位,69．8％幼虫死于林冠下,30．2％死于树皮裂缝。由此推断,流行病始于越冬期,而流行高峰始于4月中旬之前。流行区松毛虫的体长和对照区无显著差异,但雌雄比远高于对照区,而产卵量则显著低于对照区。     

醋栗透翅蛾发生危害与防治

醋栗透翅蛾是近年来严重危害黑穗醋栗的主要害虫。经观察发现 ,该虫 1年发生 1代 ,以 3龄以上老熟幼虫在枝条髓部越冬。 5月中旬老熟幼虫开始化蛹 ,6月中、下旬至 7月上旬为成虫羽化盛期。幼虫孵化后先蛀食腋芽、叶片、叶柄、嫩树皮 ,之后钻入枝条髓部蛀食危害。可在幼虫孵化初期和成虫羽化高峰期喷施化学药剂 ,防治效果较佳     

寄主及林分结构对油茶蓝翅天牛产卵选择性的影响

近年来,油茶蓝翅天牛在南方油茶各主产区发生普遍,为害严重.通过对江西油茶三大主产区蓝翅天牛产卵情况的系统调查,从生态角度分析研究了油茶枝条、林分因子等对蓝翅天牛成虫产卵选择性的影响.结果 表明,油茶蓝翅天牛成虫在产卵部位空间分布上具有较强的选择性,最喜欢选择在枝龄5～6年、枝角小于60°、枝径1.5～2.2 cm、枝高...     

甘薯品种对疮痂病的抗性及其机理分析

为查明我国南方甘薯主栽品种抗疮痂病的能力,用疮痂菌孢子悬液对16份品种作苗期接种与田间病情系统观察.结果表明,广薯79-15、潮薯1号等8份表现感病-中感;福薯26、广薯88-70等8份表现中抗-高抗;不同抗、感品种在田间表现长短不一的感病期.对6份品种藤蔓不同的部位和株龄的组织结构作显微测量与计数、接种试验以及糖含量测定显示,不同品种皮层组织结构差异决定对疮痂病的抗、感性;抗病品种藤蔓具有较厚的角质层,叶片气孔和幼嫩组织的腺鳞数目都较少,表现潜育期长,病斑少.且同一品种不同株龄皮层结构差异与感病程度间有密切关系,但其藤蔓糖含量与品种抗性之间不相关.     

中华稻蝗Knickkopf(Knk)基因分子特性和生物学功能

基于中华稻蝗转录组数据库,采用生物信息学方法搜索获得1条OcKnk基因全长cDNA序列,采用qRT-PCR检测其组织部位表达特性和其在表皮发育过程中表达情况,明确其分子特性,采用RNAi技术结合表型观察,研究其对中华稻蝗蜕皮和生长发育的影响,以明确其生物学功能。组织部位表达结果显示其在中华稻蝗体壁、前肠和脂肪体表达最高,发育表达结果显示其在表皮不同发育日龄均有表达,且在蜕皮前期和后期表达显著高于其他日龄。生物学功能研究表明,注射dsRNA后,多数虫体难以成功蜕去旧表皮,导致死亡,少部分可蜕至下一龄期,但活动力较低,行动缓慢,最终死亡。研究结果表明OcKnk参与昆虫生长发育和蜕皮过程,可作为重要靶标基因,为下一步害虫防治提供理论基础。     

Pathogenicity of four blue-stain fungi associated with aggressive and nonaggressive bark beetles

ABSTRACT The pathogenicity of two isolates of each of four bark beetle-associated blue-stain fungi was evaluated after mass inoculation of about 40-year-old Norway spruce trees (Picea abies). Trees were inoculated with a different isolate of each fungus in 1995 and 1996 at a density of 400 inoculations per m(2) in a 1.2-m-wide band on the lower bole (about 270 inoculations per tree). Trees were felled 15 weeks after inoculation. In 1995, Ceratocystis polonica was the only fungus that had stained the sapwood (56.3% of cross-sectional sapwood area). It induced five times longer phloem necroses, 21 times more dead cambium, and 11 times more dead phloem than any other fungus. In 1996, C. polonica induced less extensive host symptoms and an unidentified Ambrosiella sp. induced comparable symptoms to C. polonica in the phloem and cambium. No trees showed any foliar symptoms 15 weeks after inoculation, but six out of eight trees inoculated with C. polonica in 1995 had only 0 to 25% functional sapwood and probably would have died if felling had been delayed. This study confirms that C. polonica, an associate of the aggressive bark beetle Ips typographus, is pathogenic to Norway spruce. The pathogenicity of the Ambrosiella sp., which is associated with a nonaggressive bark beetle, seems moderate and varies between isolates. The two remaining fungi included in this study (Ophiostoma piceae and a dark fungus with sterile mycelium), which are associated with nonaggressive bark beetles, were nonpathogenic in both experiments. These results are consistent with the hypothesis that aggressive bark beetle species vector virulent fungi that may help them kill trees, but the results also show that some nonaggressive bark beetles may vector phytopathogenic fungi.     

Phloem transport of xenobiotics in Ricinus communis var. Gibsonii

Whole plants of Ricinus communis var. Gibsonii were used to study the mobility of some xenobiotics in the phloem. Solutions of ¹⁴C- or ³⁵S-labelled test compounds were introduced directly into the hollow petiole of a leaf that was exporting assimilates. Translocation was monitored by collecting phloem exudate from an incision in the stem bark beneath the treated leaf. Using [³H]sucrose as an internal standard, qualitative and quantitative results were obtained for a variety of model compounds, including herbicides, fungicides and a nematicide.     

Real-time PCR-based monitoring of DNA pools in the tri-trophic interaction between Norway spruce, the rust Thekopsora areolata, and an opportunistic ascomycetous Phomopsis sp

The difficulty in subculturing biotrophic fungi complicates etiological studies related to the associated plant diseases. By employing internal transcribed spacer rDNA-targeted quantitative real-time polymerase chain reaction, we now show that the heteroecious rust Thekopsora areolata, commonly associated in natural conditions to sapling shoots and cones of Norway spruce and leaves of wild bird cherry, frequently infects nursery-grown seedlings of the conifer. A spatial sampling scheme was used to investigate seedlings and saplings of Norway spruce showing phloem necrosis: the highest concentration of DNA of T. areolata was recorded in the area with necrotic phloem. The separate analysis of bark and wood tissues suggested that the initial spread of the rust to healthy tissues neighboring the infection site takes place in the bark. A Phomopsis species found to coexist with T. areolata in several seedlings showed very high DNA levels in the upper part of the lesion, and even in the visually healthy proximal tissues above the lesions, which indicates that the ascomycete, most probably a secondary invader following primary infection by T. areolata, has a latent stage during early host colonization. We hypothesize that this hemibiotrophic mode of infection contributes to the successful coexistence of Phomopsis with a biotrophic rust.     

太阳辐射与苹果树腐烂病早春发病的关系以及树干保护的防腐作用

 苹果树腐烂病在早春有一次发病高峰,在此高峰期,主干、主枝上的原发病斑的分布具有明显的方位倾向。不同方位的树皮受日光照射后,皮温比气温高,其增温幅度愈大,增温持续时间愈长,则该方位上的发病点愈密集。因而认为腐烂病早春发病所表现的方位性与此期间树皮受日光照射后的增温有关。按风速1.1~3.8米/秒、低云量0~2级,12~14点阳光直射面树皮温度与气温间的关系可以直线回归式表之;t_{b (皮温)}=7.70+1.93t_{a (气温)}。河北省二、三月份由阳光辐射引起树皮增温的条件经常存在。采用秋后涂白保护树体的常发病部位可以降低早春树皮增温、减轻病害,推荐桐油皂白涂剂。     

A PRELIMINARY INVESTIGATION OF THE PENETRATION AND TRANSLOCATION OF 2,4,5-T IN SOME TROPICAL TREES

Summary The relative mobility of ¹⁴C-labelled 2,4,5-T in the trunks of four different tree species was tested in dry and wet seasons, with the intention of observing the difference in translocation pattern between the susceptible ( Piptadeniastrum africanum, Celtis mildbraedii ) and the tolerant ( Xylopia quintasii, Ricinodendron heudelotii ) species, Nine trees were analysed altogether. There was a consistent pattern of adsorption and retention of the arboricide by the phloem of the four sensitive trees and downward movement of the material was marked, but in the five resistant trees the chemical was distributed upward to a greater extent in the transpiration stream. Thus in the susceptible species where there is more phloem movement the chcmical is least mobile, whereas in the tolerant ones where the chemical moves in the xylem, it is most mobile. Both types of investigation (longitudinal and radial) indicate that the killing action in the sensitive species is due to the retention of the chemical by the phloem, and that its failure to kill the tolerant trees is due to the upward movement in the transpiration stream via the xylem.     

Bioassays on Leptographium wingfieldii, a Bark Beetle Associated Fungus, with Phenolic Compounds of Scots Pine Phloem

The fungicidal activity of five phenolic metabolites occurring in Scots pine phloem (Cat, Tax, PS, PC and PSM) and of phenolic extracts from unwounded (fresh) and wounded phloem of Scots pine were measured against Leptographium wingfieldii, a fungus associated with Tomicus piniperda. Bioassays were performed in micro-wells in a standard medium in the absence and presence of Scots pine phloem. In both media, methanol extracts from the unwounded and wounded phloem, PS, PSM and PC inhibited fungal growth. Tax and Cat had no effect or stimulated fungal growth. The presence of Scots pine phloem in the liquid medium reduced the inhibitory effect of phenolic compounds. At low concentrations (10–4–10–5M), the fungus seemed to be able to degrade PS, PSM and PC while, whatever the Cat and Tax concentrations, it did not seem to degrade them. These results suggest that three phenolic compounds have a potential fungitoxicity in vitro and that, in vivo, these phenols could play a role in the efficiency of the induced reaction to stop fungal growth.     

茶蚜在茶树不同部位上刺探行为的差异

电子学穿刺记录技术(EPG)研究表明,茶蚜口针在茶树芽下第1叶、芽头、嫩茎和第4叶韧皮部中分泌(E1)和吸食(E2)的历时分别占总试验时间的30.6%、22.8%、9.6%和5.4%,差异显著(P＜0.05).在第1叶上,多数供试茶蚜的口针第1次刺探就能够深入韧皮部、分泌消化液而产生E1波,第1次在韧皮部中的分泌(E1)就能引发从韧皮部的吸食(E2).但在芽头、嫩茎和第4叶上,只有少数供试茶蚜有这样的刺吸活动.证实茶蚜嗜好第1叶.该习性与第1叶的营养组分和物理特性相关.