不同油茶种和品种对炭疽病的抗性观察

在林间调查了广东省内栽培的高州油茶、广宁红花油茶和39个品种的普通油茶对油茶炭疽病的抗病性,并在室内研究了高州油茶、广宁红花油茶和9个品种的普通油茶叶片对炭疽病的抗病性。林间自然状态下调查结果表明,广宁红花油茶对炭疽病的抗病性最强,普通油茶‘粤韶77-1号’、‘铁城1号’和‘湘林1号’抗性中等,其他品种均表现为感病;室内测定结果表明,广宁红花油茶属于抗病种类,‘铁城1号’和‘粤韶77-1号’属于中度抗病品种,其他为感病品种。     

辣椒炭疽病菌Colletotrichum gloeosporioides对啶氧菌酯的敏感基线及抗性突变体生物学性状

为评估辣椒炭疽病菌Colletotrichum gloeosporioides对啶氧菌酯的抗性风险,建立了辣椒炭疽病菌对啶氧菌酯的敏感基线,室内筛选获得了辣椒炭疽病菌抗啶氧菌酯突变体,并对突变体生物学性状进行了研究。在山西省3个未使用过啶氧菌酯及QoI类药剂的地区采集并分离到45株辣椒炭疽病菌。采用菌丝生长速率法测定其对啶氧菌酯的敏感性,结果显示,EC_(50)值介于1.404~16.650μg/mL,平均EC_(50)值为(6.783±3.499)μg/mL。啶氧菌酯与水杨肟酸(SHAM)共同处理时(SHAM的处理浓度为100μg/mL),EC_(50+S)为0.022~0.275μg/mL,平均(0.109±0.058)μg/mL,EC_(50+S)呈连续性单峰曲线,且敏感性频率分布呈近似正态分布,EC_(50+S)平均值可作为辣椒炭疽病菌对啶氧菌酯的敏感基线。且水杨羟肟酸旁路氧化贡献值F(F=EC_(50)/EC_(50+S))最低为6.039,最高为301.441,平均78.026。室内诱导获得8株抗性突变体,其中低抗突变体6株,中抗突变体2株。中抗突变体无性繁殖10代,其抗性可稳定遗传。突变体产孢量和菌丝生长速率与敏感菌株相比均无显著差异,但无药条件下,突变体致病力较敏感菌株有所降低。抗感菌株均以淀粉作为碳源、硝酸钾作为氮源时利用率最高;最适pH均为5和6;菌丝的最适生长温度均为25℃。表明辣椒炭疽病菌抗啶氧菌酯突变体具有较高的适合度,对啶氧菌酯具有较高抗性风险,这一研究结论为指导生产用药,延缓抗药性发展提供理论依据。     

油茶果皮解剖结构与炭疽病抗性的关系

本文研究了油茶炭疽病抗性与其主要果皮结构的关系,为进一步了解油茶的抗病机制、从果皮结构角度出发选育抗病良种提供理论依据。以‘普通油茶’的不同抗感炭疽病的果实为试材,分别测定其果皮蜡质层厚度、角质层厚度、气孔大小和表皮毛密度等指标。结果表明,不同抗感炭疽病的油茶果皮的总厚度、蜡质层、角质层和薄壁组织的厚度,均以高抗类型(两个高抗类型的均值)为最大,分别为5.33×103、35.67、25.85、87.73μm,高感类型为最小,分别为2.77×103、19.33、9.67、48.33μm;随着油茶果实抗病性增强,果皮气孔开度、密度和单位气孔面积均呈现明显的下降趋势,以高感类型为最大,分别为38.58μm2、22.02个/mm2和670.50μm2,高抗类型最小,分别为12.59μm2、5.05个/mm2和82.21μm2,但气孔大小与其炭疽病抗性没有明显相关性;抗病类型的油茶果皮表皮毛长度、粗度和密度,均明显大于感病类型。油茶果皮解剖结构与炭疽病抗性关系极为密切,可以作为鉴定油茶炭疽病抗性强弱的参考指标。     

辣椒炭疽病菌对嘧菌酯的敏感性测定

 从江苏和海南省随机采集分离获得45个辣椒炭疽病菌单孢菌株,根据孢子形态鉴定其病原菌为Colletotrichum gloeosporioides和C.capsici,其中C.gloeosporioides占总菌株数的64.4%.筛选出甘油琼脂(AEA)培养基和水琼脂(WA)培养基,分别作为产孢法和孢子萌发法测定辣椒炭疽病菌对嘧菌酯敏感性的适宜培养基.通过孢子萌发法测定2种病原菌45个菌株对嘧菌酯的敏感性范围在0.009~0.091μg/mL之间,平均EC₅₀为(0.047±0.040)μg/mL.其中29个C.gloeosporioides菌株和16个C.capsici菌株的平均EC₅₀值分别为(0.051±0.047)μg/mL和(0.041±0.024)μg/mL.研究发现旁路氧化酶抑制剂水杨肟酸(SHAM)对嘧菌酯抑制分生孢子萌发有协同增效作用,且嘧菌酯抑制辣椒炭疽病菌菌丝生长的能力较弱.     

Molecular and biochemical characterization of Colletotrichum gloeosporioides isolates resistant to azoxystrobin from grape in China

Anthracnose, caused by Colletotrichum gloeosporioides, is one of the most important diseases in grape-growing regions worldwide. In Jiangsu Province of China, quinone-outside inhibitor fungicides (QoIs) have been extensively sprayed as disease control for more than 10 years. A spore germination assay of 64 isolates obtained from 32 commercial vineyards was used to assess isolate sensitivity to azoxystrobin and 62 were found to be resistant to azoxystrobin. The biological fitness of QoI-resistant (QoI^R) isolates was significantly lower than the sensitive isolates (QoI^S) in terms of mycelial growth and conidiation. Nucleotide sequence alignment of CgCytb genes from the QoI^R and QoI^S isolates revealed that two point mutations (F129L and G143A) are involved in the QoI resistance. Isolates with the G143A mutation expressed high resistance to azoxystrobin, whereas isolates carrying the F129L mutation exhibited moderate resistance. Positive cross-resistance was observed between azoxystrobin and kersoxim-methyl, pyraclostrobin, or benzothiostrobin, but not with fluazinam. This study provides important information for management of QoI^R populations of C. gloeosporioides in the field.     

Histological and proteomics analysis of apple defense responses to the development of Colletotrichum gloeosporioides on leaves

Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. is an important fungal pathogen known to cause glomerella leaf spot (GLS). The objective of this study was to analyze the infection of C. gloeosporioides on leaves of apple cv. Fuji (resistant) and cv. Gala (susceptible) and apply proteomics techniques to study the apple defense responses 48 h after inoculation (h.a.i.). On both of cultivars, C. gloeosporioides started to germinate at 3 h.a.i. on adaxial surface and produced appressoria adhering to epidermal cell juxtapositions. Histological analysis showed more stratified parenchyma in leaves of cv. Fuji than cv. Gala associated with differences in the chemical composition of cell walls. Total and unique proteins expressed by cvs. Fuji and Gala at 3, 12, 24 and 48 h.a.i. were detected by comparative proteomes analysis. A total of 42 unique proteins expressed at 24 and 48 h.a.i. were identified by MALDI/TOF mass spectrometry, and most of these proteins were identified as directly involved in defense responses.     

Sensitivity of Colletotrichum gloeosporioides species complex (CGSC) isolated from strawberry in Taiwan to benzimidazole and strobilurin

Colletotrichum gloeosporioides species complex (CGSC) is the major pathogen causing strawberry anthracnose in Taiwan. Benzimidazoles and strobilurins are common fungicides used to control strawberry anthracnose. A total of 108 CGSC isolates were collected from five major strawberry-producing areas in Taiwan. The half-maximal effective concentration (EC₅₀) values of most CGSC isolates for benomyl (59 isolates), carbendazim (70 isolates), and thiabendazole (63 isolates) were higher than 500 µg a.i./mL. Strobilurin tests showed that the EC₅₀ values of most CGSC isolates for azoxystrobin (66 isolates), kresoxim-methyl (42 isolates), and trifloxystrobin (56 isolates) were higher than 500 µg a.i./mL. However, most CGSC isolates were sensitive to pyraclostrobin at 100 µg a.i./mL. Fungicide tests indicated that CGSC isolates show multi-resistance to benzimidazoles and strobilurins. Benzimidazole-resistant isolates were associated with a point mutation in codon 198 of the β-tubulin gene, and strobilurin-resistant isolates did not correspond with mutation in the cyt b gene or alternative oxidase activity.     

Enhancing Resistance of Tomato and Hot Pepper to Pythium Diseases by Seed Treatment with Fluorescent Pseudomonads

Twenty isolates of fluorescent pseudomonads were evaluated for their ability to control damping-off in tomato (Lycopersicon esculentum) and hot pepper (Capsicum annuum). These isolates were characterized as Pseudomonas fluorescens and Pseudomonas putida. Two isolates, PFATR and KKM 1 belonged to P. putida and the remaining 18 isolates belonged to P. fluorescens. Among these isolates, P. fluorescens isolate Pf1 showed the maximum inhibition of mycelial growth of Pythium aphanidermatum and increased plant growth promotion in tomato and hot pepper. P. fluorescens isolate Pf1 was effective in reducing the damping-off incidence in tomato and hot pepper in greenhouse and field conditions. Isolate Pf1 was further tested for its ability to induce production of defense-related enzymes and chemicals in plants. Earlier and increased activities of phenylalanine ammonia lyase (PAL), peroxidase (PO) and polyphenol oxidase (PPO) were observed in P. fluorescens Pf1 pretreated tomato and hot pepper plants challenged with Pythium aphanidermatum. Moreover, higher accumulation of phenolics was noticed in plants pretreated with P. fluorescens isolate Pf1 challenged with Pythium aphanidermatum. Thus, the present study shows that in addition to direct antagonism and plant growth-promotion, induction of defense-related enzymes involved in the phenyl propanoid pathway collectively contributed to enhance resistance against invasion of Pythium in tomato and hot pepper.     

云南派姬小蜂对其寄主及寄主植物相关化学线索的行为反应

与寄主植物和寄主相关的化学线索在寄生蜂的寄主搜寻过程中起着重要作用。云南派姬小蜂Pediobius yunnanensis是松树钻蛀性害虫——微红梢斑螟Dioryctria rubella的蛹寄生蜂,为了探究该寄生蜂对其寄主和寄主植物相关化学线索的行为反应,本研究进行了一系列试验。利用Y形嗅觉仪,测定了该寄生蜂对不同处理的油松球果（含蛹球果、含空蛹壳的球果、幼虫为害的球果和健康球果）和松枝（含蛹松枝、幼虫为害的松枝、含蛹球果的系统枝、含蛹松枝的系统枝和健康松枝）以及幼虫虫粪（3龄幼虫虫粪、含蛹球果内的幼虫虫粪）挥发物的趋性行为;在开放场中,测定了老熟幼虫爬行痕迹对该寄生蜂搜索行为的影响;利用双选择试验,在培养皿中测定了该寄生蜂对微红梢斑螟茧或蛹浸提液的行为反应。结果显示,在嗅觉试验中,含蛹球果、含有空蛹壳的球果挥发物对寄生蜂有极显著的引诱作用,而幼虫为害的球果和健康球果对寄生蜂的行为无明显影响;该寄生蜂对含蛹松枝挥发物表现出明显的正趋性反应,而对幼虫为害的松枝、含蛹球果的系统枝、含蛹松枝的系统枝以及健康松枝则无趋性反应;寄生蜂对含蛹球果中的幼虫虫粪挥发物表现出偏爱性,而对3龄幼虫虫粪无明显反应;在开放场中,老熟幼虫的爬行痕迹对寄生蜂的搜索行为无显著影响;在培养皿中,微红梢斑螟茧的甲醇、二氯甲烷或正己烷浸提液以及蛹的二氯甲烷或正己烷浸提液,不仅能强烈地吸引该寄生蜂,还能明显延长其停留时间。该结果为揭示云南派姬小蜂寄主搜寻行为的化学调控机制以及微红梢斑螟的生物防治提供理论依据。     

Infection of Cranberry Flowers by Monilinia oxycocci and Evaluation of Cultivars for Resistance to Cottonball

ABSTRACT Infection of cranberry flowers by conidia of Monilinia oxycocci, the cottonball pathogen, was investigated using a squash-mount histological method. Conidia germinated on anthers, nectaries, petals, and stigmata, but not styles. The stigma was the only flower part penetrated by the fungus, but no specialized infection structures were noted. Both fungal and pollen germ tubes grew through the stylar canal and made contact with ovules and nucellar tissue by 72 h after inoculation and pollination. Cottonball incidence was greatest when stigmata were inoculated; the low level of cottonball that resulted from inoculation of other flower parts and in noninoculated flowers was attributed to contamination of stigmata. In greenhouse tests, cottonball incidence was 25, 28, 31, and 38% for cvs. Searles, Pilgrim, Ben Lear, and Stevens, respectively, and was greater for M. oxycocci isolate 593 than isolate 591. We conclude that the stigma is the sole floral infection court for conidia of M. oxycocci and that the most popular cranberry cultivars in Wisconsin do not differ in inherent resistance to cottonball. The relevance of these findings to the long-term management of cottonball is discussed.     

Sensitivity of Red Delicious Apple Fruit at Various Phenologic Stages to Infection by Alternaria alternata and Moldy-core Control

The fungus Alternaria alternata, is considered to be the predominant fungus involved in moldy-core of Red Delicious strains of apple. In this paper, we report on the sensitivity of various phenologic stages to infection by A. alternata, and on the efficacy of various fungicides in controlling moldy-core disease in apple orchards. Artificial inoculations conducted in the orchard during 1999 and 2000 seasons revealed that the beginning of bloom (10–30%) and full bloom were the most susceptible developmental stages for infection. Natural infection with A. alternata in fruits was relatively high, reaching 44% and 46% of the fruits on control non-treated trees in 1999 and 2000. Four foliar applications of polyoxin B, difenoconazole and azoxystrobin, starting from the beginning of bloom until fruit set, reduced the number of infected fruits by 54–70%, 61–70% and 50–65%, respectively, compared with non-treated trees. Four or eight foliar applications of each fungicide provided similar levels of control. There were no significant differences between two, four or six foliar applications of difenoconazole, neither between two or four applications of polyoxin B. Adding CaCl₂, as a tank mixture with difenoconazole at full rate, did not improve efficacy. Alternaria was recovered from the inner part of the core region of 71–88% of the fruits of the non-treated control, but was recovered less frequently from the outside part of the core region. Fruits of difenoconazole and polyoxin B treated trees were less colonized with A. alternata at both the inner and outside parts of the core region, as compared with controls. Results indicate that a control programme based on spray applications of difenoconazole or polyoxin B, during bloom period, can effectively reduce Alternaria on Red Delicious.     

烟粉虱与温室白粉虱羧酸酯酶、谷胱甘肽转移酶和乙酰胆碱酯酶性质的比较研究

对温室白粉虱 Trialeurodes vaporariorum和烟粉虱 Bemisia tabaci羧酸酯酶(Car E)、乙酰胆碱酯酶 (ACh E)和谷胱甘肽转移酶 (GSTs)的生物化学性质进行了初步研究。比较 Car E活性 ,烟粉虱显著高于温室白粉虱 ,烟粉虱和温室白粉虱 Car E对底物乙酸 -α-萘酯的 Km 分别为 0 .073mmol/ L 和 3.458mmol/ L。烟粉虱 ACh E活性分布高峰在 2～3m OD/ (min·头 )之间 ,而温室白粉虱 ACh E活性分布高峰在 10～ 15 m OD/ (min·头 )之间 ,烟粉虱 ACh E的 Km 值是温室白粉虱 Km 值的 12 .6倍。烟粉虱的 GSTs比活力为2 .218OD/ (mg pro·min) ,显著高于温室白粉虱的 GSTs比活力 0 .663OD/ (mg pro· min) ,差异达极显著水平 ,烟粉虱 GSTs对底物的亲和力比温室白粉虱高。     

Susceptibility of Clematis Varieties and Species to Stem Infection by Phoma Clematidina as an Indicator for Resistance to Wilt

The susceptibility to stem rot and wilt caused by Phoma clematidina was tested for a range of clematis varieties and species widely grown in Europe, and compared with their susceptibility to wilt in practice as judged by amateur and commercial growers in two postal surveys. Most small flowering clematis species did not die back when unwounded stems were inoculated with spores of P. clematidina, and were also reported in the surveys as being very resistant to wilt. In contrast, large flowering hybrids were found to be highly susceptible both to stem infection by P. clematidina and to wilt in practice according to growers. A significant positive linear relationship existed between the susceptibility scores for disease in the stem inoculation test and those for wilt from the surveys. Fungal isolations were made from the stems of naturally wilted clematis plants from British nurseries and private gardens. Unlike the many other fungal species isolated, P. clematidina occurred very frequently, especially in stems of large flowering varieties. Together with the results from the grower surveys and stem inoculation trial, this indicates that this fungus is a regular cause of clematis wilt. The stem inoculation test with P. clematidina described in this study would be useful for European breeders and growers to determine the susceptibility of new clematis varieties to wilt before they are marketed.     

Laboratory Evaluation of Citrus Cultivars Susceptibility and Influence of Fruit Size on Fortune Mandarin to Infection by Alternaria alternata pv. citri

Young leaves of 62 citrus cultivars were inoculated with conidia of three Spanish isolates of Alternaria alternata pv. citri, the causal agent of brown spot of citrus. Hybrids with Dancy mandarin, King mandarin or their derivates as a parent, grapefruit cultivars and the mandarin cultivars Guillermina, Emperor, Clemenpons and Esbal were highly susceptible to the pathogen. Satsuma cultivar Clausellina and orange cultivars, with the exception of Sanguinelli, were slightly susceptible. Lemon and lime cultivars were not susceptible, with the exception of Mexican lime (Citrus aurantifolia), which was slightly susceptible. Although this study shows a range of potential hosts for this pathogen, to date the only affected cultivars in Spain are Fortune and Nova mandarins, and Minneola tangelo. The susceptibility of Fortune fruits decreased as diameter increased, being susceptible through the whole season. This was confirmed with field observations in autumn where fruit infections have been detected when the diameter reaches 6–7 cm.     

Evaluation of Induction of Systemic Resistance in Pepper Plants (Capsicum Annuum) to Phytophthora capsici Using Trichoderma harzianum and its Relation with Capsidiol Accumulation

The effect of pepper seed and root treatments with Trichoderma harzianum spores on necrosis caused in stems by Phytophthora capsici inoculation and on the course of capsidiol accumulation in the inoculated sites were studied. The results indicate that seed treatments significantly reduced stem necrosis, which fell by nearly a half compared with the values observed in plants grown from non-treated seeds. Necrosis was also reduced in plants whose roots were drenched with various doses of T. harzianum spores, although the extent of necrosis was not correlated with the dose used. Attempted isolation of P. capsici and T. harzianum from the zones immediately contiguous with the necrotic zones revealed the presence of the former but not of the latter, suggesting that there was no direct contact between them in the zones of isolation, which means that there was no competition for space. The percentage of P. capsici isolated 9 days after inoculation was greater in non-treated inoculated plants than in treated inoculated plants. These results suggest that T. harzianum, introduced into the subterranean part of the plant, induces a systemic defense response against P. capsici in the upper part of the plant. Analysis of capsidiol in the stems of treated inoculated plants by the end of the sixth day after inoculation, revealed that its concentration was more than seven-fold greater than in non-treated and inoculated plants, while after 9 days, the concentration of capsidiol decreased in the treated inoculated plants and increased in the non-treated inoculated plants. The high concentration of capsidiol detected in treated and inoculated stems after 6 days might be one of the contributing factors, but not necessarily the main factor, in delaying lesion development in the stems of pepper plants.     

Identification of a Maize Kernel Pathogenesis-Related Protein and Evidence for Its Involvement in Resistance to Aspergillus flavus Infection and Aflatoxin Production

ABSTRACT Aflatoxins are carcinogens produced by Aspergillus flavus and A. parasiticus during infection of susceptible crops such as maize. Several aflatoxin-resistant maize genotypes have been identified and kernel proteins have been suggested to play an important role in resistance. In the present study, one protein (#717), which was expressed fivefold higher in three resistant lines compared with three susceptible ones, was identified using proteomics. This protein was sequenced and identified as a pathogenesis-related protein (PR-10) based on its sequence homology. To assess the involvement of this PR-10 protein (ZmPR-10) in host resistance of maize against fungal infection and aflatoxin production, the corresponding cDNA (pr-10) was cloned. It encodes a protein of 160 amino acids with a predicted molecular mass of 16.9 kDa and an iso-electric point of 5.38. The expression of pr-10 during kernel development increased fivefold between 7 and 22 days after pollination, and was induced upon A. flavus infection in the resistant but not in the susceptible genotype. The ZmPR-10 overexpressed in Escherichia coli exhibited a ribonucleolytic and antifungal activities. Leaf extracts of transgenic tobacco plants expressing maize pr-10 also demonstrated RNase activity and inhibited the growth of A. flavus. This evidence suggests that ZmPR-10 plays a role in kernel resistance by inhibiting fungal growth of A. flavus.     

浸种专用型水稻种衣剂对水稻秧苗生长及 抗病性相关酶活性的影响

试验证明, 硫与三环唑(7∶1) 混配成悬浮剂, 对抑制稻瘟菌的菌丝生长、分生孢子萌发、附着胞的形成以及产孢能力等都具有较明显的协同增效作用, 协同作用比率(S R ) 分别为2. 1、2. 5、1. 8 及8. 6。混配剂集合了硫及三环唑两者的优点, 并显示出耐雨水冲刷、持效期长的特点。田间试验亦表明其防病增产效果比较显著。