Integrated Pest Management in Cocoa Agroforests in Southern Cameroon: Constraints and Overview

Imports of pesticides have long been subsidised for use in the cocoa agroforests of the humid forest zone of southern Cameroon. With the liberalisation of the cocoa and pesticides sectors and the devaluation of the local currency (CFA franc), farmers are facing fluctuations in the price paid for cocoa and the high cost of farm inputs. Without the support of the extension services, they themselves have developed traditional integrated control methods based on the use of plant extracts mixed with conventional pesticides. From a survey of 300 cocoa farmers, the study assesses the farmers' command of these methods, the pests controlled, the problems encountered and the institutional constraints in the definition and dissemination of integrated control methods. The study concludes with recommendations for research and development towards the better definition and dissemination of integrated control methods. This revised version was published online in July 2006 with corrections to the Cover Date.     

β- 氨基丁酸诱导甜( 辣) 椒抗疫病作用的研究

 报道了用β- 氨基丁酸( DL-β-aminon-butyric acid, BABA) 喷雾处理辣椒叶片和茎后的诱导抗疫病作用。研究证明: 高浓度BABA ( 1 000 g/mL) 对离体辣椒疫霉病菌无抗菌活性, 用其喷雾处理辣椒的茎叶所诱导的抗疫病作用可完全控制其危害; 用BABA 诱导处理后3 d 接种辣椒疫霉病菌, 辣椒植株开始表达出较高的诱导抗性, 这种抗病作用可持续20 d 以上, 并表现出与数量抗病性相似的特性。     

Suppression of wheat-seedling diseases caused by Fusarium culmorum and Microdochium nivale using bacterial seed treatment

Snow mould, caused by Microdochium nivale , and seedling blight caused by members of the Fusarium complex, are cereal diseases of great economic importance in many temperate zones. In a glasshouse bioassay designed to enhance disease, about 600 plant-associated bacterial isolates obtained by different methods were screened for suppressive effects in wheat against infection caused by Fusarium culmorum . Although most of the isolates tested had a neutral effect on test plants and disease development, a few were synergistic to the pathogen and about one-fifth showed > 80% disease suppression. During five consecutive growing seasons, 164 bacterial isolates were tested in field experiments against both F. culmorum and M. nivale as causal agents of seedling blight. Tests for effects on yield in experiments with spring and winter wheat, performed in different climatic regions of Sweden, showed that disease-suppressive effects were repeatable. The most efficient isolates, three fluorescent pseudomonads and a species of Pantoea , suppressed disease equal to that of the fungicide guazatine, both with respect to crop stand and yield. Seed treatment with Pantoea sp. (isolate MF 626) increased yield by an average of more than 500 kg ha⁻¹ in six field experiments.     

Genetic variation among asexual progeny of Phytophthora infestans detected with RAPD and AFLP markers

Genotypic variation among 32 single-zoospore isolates (SZI) of Phytophthora infestans , derived asexually from two hyphal-tip parental isolates (PI-105 and PI-1) of the US-8 genotype, was assessed with 80 random amplified polymorphic DNA (RAPD) primers and 18 amplified fragment length polymorphic DNA (AFLP) primer pairs. In previous investigations, the SZIs from parental isolate PI-105 showed high levels of virulence variability and were differentiated into 14 races, whereas the SZIs from PI-1 showed identical virulence to the parent. The purpose of this investigation was to determine if phenotypic variation observed among SZIs of P. infestans could be detected at the DNA level in these isolates. Polymorphism was detected with 51 RAPD primers and with all 18 AFLP primer pairs in PI-105 SZIs. In SZIs from PI-1, polymorphism was also detected with 25 RAPD primers and 17 AFLP primer pairs. Cluster analysis using the unweighted pair-group method with arithmetic averages (UPGMA) separated the SZIs from parent PI-105 into six virulence groups, 11 RAPD groups and three AFLP groups. Cluster analysis of PI-1 SZIs, which all belong to the same virulence group, differentiated them into four RAPD groups and six AFLP groups. No close correlation among RAPD, AFLP and virulence groups could be established within the two progenies of SZIs. Results of this study suggest that there is a considerable level of inherent genetic variability among SZIs derived asexually from the same parental isolate. The possible mechanisms and implications of this genetic variation are discussed.     

哈茨木霉几丁质酶诱导及其对水稻纹枯病菌的拮抗作用

 在实验室条件下分别以几丁质和水稻纹枯病菌(Rhizoctonia solani)细胞壁作唯一碳源诱导哈茨木霉(Trichoderma harzianum)菌株NF9、TC3和P1产生几丁质酶,用硫酸铵沉淀法制备几丁质酶粗提液。上述木霉菌株内切几丁质酶活性(对胶体几丁质浑浊度的减少率)分别为79.8%、74.4%和76.0%,均显著高于非诱导的阳性对照。培养第5 d几丁质诱导的木霉菌株NF9和TC3内切几丁质酶活性显著高于由水稻纹枯病菌细胞壁诱导的酶活性。体外测定表明,通过诱导的木霉菌株TC3、NF9和P1几丁质酶粗提液对水稻纹枯病病菌的拮抗圈直径可达38、21和23 mm,与非诱导的阳性对照比较有显著性差异。对木霉几丁质酶拮抗作用的特点及生防应用进行了讨论。     

中国18 省市番茄晚疫病菌生理小种的鉴定

 利用5 个含有不同单显性抗番茄晚疫病基因的番茄材料Ts19、Ts33、W1Va700、LA1033 和L3708为鉴别寄主, 对我国18 省、市、自治区的番茄晚疫病菌201 个纯化分离物进行了生理小种鉴定。结果共鉴定出8 个小种, 即生理小种T0、T1、T1 ,2 、T1 ,2 ,3 、T1 ,2 ,3 ,4 、T1 ,4 、T1 ,2 ,4 和T3。其中, 小种T1 和T1 , 2是主流小种, 地理分布最广和发生频率最高, 分别在13 和11 个省市出现, 占样本总数的28.8 %和28.4 %;其次是小种T0 和T1 ,2 ,3 , 分别在8 和7 个省市出现, 分别占1819 %和819 %; 再其次是小1 ,2 ,3 ,4 , 在4个省市有发生, 占710 %; 小种T1 ,2 ,4 、T1 ,4 和T3 分布均少, 仅在1～2 个省市发生, 分别占3.0 %、2.5 %和2.5 %。这是我国的首次报道, 为番茄晚疫病的抗源材料筛选和抗病育种提供了病理学依据。     

红掌细菌性疫病的病原菌初步鉴定

 在云南西双版纳的红掌上发现一种由细菌侵染引起的病害,从叶片的病组织上分离到具有致病性的杆状细菌,将分离的病原菌接种于健康的红掌上,表现出与田间一致的症状。感病初期在叶缘或叶脉间出现水渍状小点,后期病斑多呈棕褐色至黑色坏死,病健交界处多呈黄色。从接种发病的病斑与田间标样上分离的病原菌菌落形态完全相同。通过菌株的培养性状、常规生理生化特性及透射电镜下菌体形态观察结果,将病原菌初步鉴定为黄单胞菌属(Xanthomonas)。BIOLOG鉴定和致病性测定结果进一步鉴定病原菌为地毯草黄单胞菌花叶万年青致病变种Xanthomonas axonopodis pv. dieffenbachiae(Xad)(McCulloch & Pirone) Vauterin et al.     

Competition Effects Among Isolates of Fusarium culmorum Differing in Aggressiveness and Mycotoxin Production on Heads of Winter Rye

Fusarium culmorum is a phytopathogenic, toxigenic fungus causing seedling diseases, foot rot and head blight of cereals. For estimating competition effects in mixtures of two single-spore isolates, two winter rye single crosses were tested with either four isolates individually or four 1 : 1 mixtures of the same isolates in six field environments. Two isolates (FC46, FC64) were highly aggressive deoxynivalenol (DON) and 3-acetyl DON-producers, the other two (FC30, FC71) were medium aggressive nivalenol-producers. Rye heads were inoculated during flowering with conidia of pairs of isolates expressing similar (FC46 + FC64, FC30 + FC71) or contrary (FC46 + FC71, FC30 + FC64) levels of aggressiveness and similar or different concentrations and chemotypes of mycotoxins, respectively. Head blight rating and yield components relative to the non-inoculated plots were recorded as aggressiveness traits. Additionally, mycotoxin concentrations were measured in the rye grain. Random pathogen samples were re-isolated from heads at the onset of symptom development and analysed by molecular markers (RAPD–PCR) in one environment. Aggressiveness of the isolate mixtures was significantly lower than that of the isolates applied individually on both rye genotypes. Similarly, mycotoxin concentrations were significantly lower in the mixtures in seven out of eleven comparisons. Among the re-isolates, the component genotypes of a mixture significantly deviated from the inoculated 1 : 1 ratio when a particular isolate (FC46) was present in the mixture. This isolate displayed a superior competitive ability irrespective of the aggressiveness or mycotoxin profile of the mixing partner illustrating that pathogenic fitness is caused by additional factors that have not, as yet, been identified.     

Aggressiveness and host specificity of Brazilian isolates of Phytophthora infestans

The population of Phytophthora infestans in Brazil consists of two clonal lineages, US-1 associated with tomatoes and BR-1 associated with potatoes. To assess whether host specificity in these lineages resulted from differences in aggressiveness to potato and tomato, six aggressiveness-related epidemiological components – infection frequency (IF), incubation period (IP), latent period (LP), lesion area (LA), lesion expansion rate (LER) and sporulation at several lesion ages (SSLA) – were measured on detached leaflets of late blight-susceptible potato and tomato plants. Infection frequency of US-1 was similar on potato and tomato leaflets, but IF of BR-1 was somewhat reduced on tomato. Incubation period was longer on both hosts with US-1, although this apparent lineage affect was not significant. Overall there was no host effect on IP. On potato, BR-1 had a shorter LP (110·3 h) and a larger LA (6·5 cm²) than US-1 (LP = 162·0 h; LA = 2·8 cm²). The highest LER resulted when isolates of BR-1 (0·121 cm² h⁻¹) and US-1 (0·053 cm² h⁻¹) were inoculated on potato and tomato leaflets, respectively. The highest values of the area under the sporulation capacity curve (AUSC) were obtained for isolates of US-1 inoculated on tomato leaflets (6146) and for isolates of BR-1 on potato leaflets (3775). In general, higher values of LA, LER, SSLA and AUSC, and shorter values of LP were measured when isolates of a clonal lineage were inoculated on their original host than with the opposite combinations. There is evidence that there are quantitative differences in aggressiveness components between isolates of US-1 and BR-1 clonal lineages that probably contribute to host specificity of P. infestans populations in Brazil.     

云南小麦品种（系）锈病和赤霉病抗性功能基因的KASP标记检测

利用5个锈病成株期抗性基因的KASP标记Sr2_ger9 3p、Lr34jagger、CSTM4_67G、Lr68-2、VPM_SNP和抗赤霉病基因Fhb1的KASP标记TaHRC-KASP,对云南省育成的42个小麦品种（系）进行检测,旨在筛选出含有目标基因的优异小麦种质,为云南省持久抗病小麦新品种（系）的选育提供材料。结果表明,4个材料含兼抗型成株抗锈病基因Lr34/Yr18/Sr57,频率为9.52%;6个品种（系）含兼抗型成株抗锈病基因Lr67/Yr46/Sr55,频率为14.29%;7个材料含抗慢叶锈病基因Lr68,频率为16.67%;含兼抗型成株抗锈病基因Sr2/Yr30和成株抗叶锈基因Lr37的材料各有1个,频率均为2.38%;未检测出含抗赤霉病基因Fhb1的品种（系）。云麦69、云麦75、云麦56、宜麦1号和宜麦3号等兼有2个成株期抗锈病基因,可作为今后云南持久抗锈病育种的抗源材料。