Role of rainfall in the development of coffee berry disease in Coffea arabica caused by Colletotrichum kahawae,in Cameroon

The development of coffee berry disease (CBD) epidemics (caused by Colletotrichum kahawae) in Cameroon was monitored over two successive years (2004 and 2005) on coffee trees protected from rainfall by transparent plastic sheets and on unprotected control trees. This work was done to assess how rain affected disease development when it did not fall directly onto the coffee trees and to determine the influence of primary inoculum on the severity of CBD. Weekly observations over the 2 years showed that there were 1·1% diseased berries on coffee trees completely protected from rainfall, compared with 45% diseased berries on unprotected coffee trees. Disease severity on unprotected trees during the 2 years of the experiment was estimated at 53% diseased berries, compared with 27% on trees only protected in the first year. These results confirmed rainfall as one of the key physical factors in the development of Arabica CBD. They also provided evidence of a subsequent effect of protecting coffee trees from rainfall in 2004 on the severity of CBD in 2005. This suggested some practices that might lead to very effective cultural control of CBD in regions where severe epidemics of the disease occur.     

北美森林新病害——山毛榉叶线虫病

2012年,北美地区发生了一种由山毛榉李氏垫刃线虫麦肯恩亚种(Litylenchus crenatae mccannii)引起的森林新病害——山毛榉叶线虫病,病情蔓延迅速,已扩散至美国和加拿大30个县。病原为害山毛榉属植物,可造成病树成片死亡。由于山毛榉是北美温带阔叶林的主要构成树种和重要用材树种,新病害已引起美国农业部的高度重视并采取积极的应对措施。我国分布5种山毛榉属植物(均为特有种),是我国南方森林的主要组成树种。鉴于我国每年从北美进口大量山毛榉木材,病原线虫存在随进境木材传入国内的巨大风险。因此,检疫部门应开展风险评估,口岸应针对性开展山毛榉叶线虫病的检测。本文主要介绍了山毛榉叶线虫病的发生历史、分布范围、为害症状、病原线虫形态学特征、生活史、传播途径、分子检测方法等方面的信息,以期为口岸检疫工作提供参考。     

Resistance levels in Coffea arabica to Gibberella xylarioides and distribution pattern of the disease

Coffea arabica trees in a collection at Jimma, Ethiopia, are often attacked and killed byGibberella xylarioides. Statistical analysis shows a varietal pattern of attack. However, an influence of disease loci is also probable. Varietal differences open the possibility of control with resistant varieties. Localized outbreaks of the disease may permit temporary control by tree eradication and soil treatment.Samenvatting Veel bomen van een collectie vanCoffea arabica L. te Jimma sterven na een aantasting doorGibberella xylarioides Heim et Saccas. Door groepering van het materiaal op verschillende manieren (Fig. 1) zijn twee vergelijkingen mogelijk: (a) Tussen een theoretische verdeling berekend over de gehele collectie zonder plaats- of lijneffecten en een verdeling met plaatseffecten maar zonder lijneffecten (plaatseffect). (b) Tussen de verdeling zonder lijneffecten maar met mogelijke plaatseffecten en een verdeling met lijneffecten en mogelijke plaatseffecten (lijneffect).De statistische analyse (Tabel 1) toont dat het plaatseffect net niet significant is maar dat de verschillen tussen lijnen een zeer hoge significantie bezitten (Tabel 2). Verschillen in gevoeligheid tussen een aantal lijnen zijn aangegeven in Tabel 3. De vrij waarschijnlijke plaatseffecten maken bestrijding van de ziekte mogelijk door vernietiging van aangetaste bomen en bodembehandeling. De duidelijke resistentieverschillen tussen koffielijnen maken controle op lange termijn met behulp van resistentie mogelijk.FAO Coffee Pathologist and FAO Associate Expert, respectively.     

Investigations into Encephalartos insect pests and diseases in South Africa and identification of Phytophthora cinnamomi as a pathogen of the Modjadji cycad

South Africa holds the greatest diversity of Encephalartos species globally. In recent years several reports have been received of Encephalartos species in the country dying of unknown causes. The aim of this study was to investigate the presence of, and identify the causal agents of, diseases of Encephalartos species in the Gauteng and Limpopo Provinces of South Africa. Plant material with symptoms and insects were collected from diseased plants in private gardens, commercial nurseries and conservation areas in these regions. Insects collected were identified based on morphology, and microbial isolates based on morphology and DNA sequence data. Insect species identified infesting cultivated cycads included the beetle Amorphocerus talpa, and the scale insects Aonidiella aurantii, Aspidiotus capensis, Chrysomphalus aonidum, Lindingaspis rossi, Pseudaulacaspis cockerelli, Pseudaulacaspis pentagona and Pseudococcus longispinus. Fungal species isolated from diseased plants included species of Diaporthe, Epicoccum, Fusarium, Lasiodiplodia, Neofusicoccum, Peyronellaea, Phoma, Pseudocercospora and Toxicocladosporium. The plant pathogen Phytophthora cinnamomi was identified from E. transvenosus plants in the Modjadji Nature Reserve. Artificial inoculation studies fulfilled Koch's postulates, strongly suggesting that P. cinnamomi is responsible for the deaths of these plants under field conditions.     

Investigations into the Wood-pigeon Problem in Cabbage Fields during Winter

In Europe the population of the wood-pigeon ( Columba palumbus L.) is increasing, consequently agricultural and horticultural damage is also increasing, especially in cereal and Brassica fields. In Great Britain long-term investigations of this problem have been made.
In the Federal Republic of Germany, wood-pigeons cause a lot of damage to cabbage fields. Farmers, in the Mainz-Gonsenheim area, suffer damage amounting to more than DM 100,000 per annum, to their Brassica crops. This amounts to 30% of the harvest. Our Institute has started a research program to find methods of reducing the damage in cabbage fields and to test methods of controlling the pigeon populations. The investigations are supported by the Ministerium für Landwirtschaft, Weinbau und Umweltschutz in Rheinland-Pfalz.     

广西罗汉果病毒病发生情况调查

2002年对广西5个县9个乡(镇)74309株罗汉果病害调查明确,传统种植的罗汉果病毒病发病率平均为52.8％,严重的达100％;采用组培苗种植的病毒病发病率平均为13.9％,重病的达63.0％。传统的种薯种植,品种退化,人工抹芽、授粉,蚜虫传毒,以及果园附近插花种植病毒寄主植物,是广西罗汉果种植区罗汉果病毒病发生严重的原因。     

Morphological and molecular analysis of Fusarium lateritium, the cause of gray necrosis of hazelnut fruit in Italy

Fusarium lateritium is a globally distributed plant pathogen. It was recently reported as the causal agent of nut gray necrosis (NGN) on hazelnut. Isolate characterization within F. lateritium was undertaken to investigate how morphological and molecular diversity was associated with host and geographic origin. Morphological studies combined with inter-simple-sequence repeat (ISSR) analysis, and phylogenetic analyses using translation elongation factor 1α (TEF-1α), β-tubulin genes, and nuclear ribosomal DNA internal transcribed spacer (ITS) sequences were conducted to resolve relationships among 32 F. lateritium isolates from NGN-affected hazelnut fruit, and 14 from other substrates or 8 from other hosts than hazelnut. Colonies of F. lateritium from hazelnut showed dark grayish-olive differing from the orange-yellow color of all other isolates from other hosts. Generally, isolates from NGN-affected fruit failed to produce sporodochia on carnation leaf agar. The influence of host and substrate on the genetic structure of F. lateritium was supported by ISSR and analyzed with principal coordinates analysis. A relationship between hazelnut and genetic variation was inferred. Phylogenetic analysis of ITS provided limited resolution while TEF-1α and β-tubulin analyses allowed a clear separation between the European and non-European F. lateritium isolates retrieved from GenBank, regardless of host. Though morphological traits of F. lateritium isolates from hazelnut were generally uniform in defining a typical morphogroup, they were not yet phylogenetically defined. In contrast, the typology related to slimy deep orange cultures, due to spore mass, grouped clearly separated from the other F. lateritium isolates and revealed a congruence between morphology and phylogeny.     

Virulence and Molecular Diversity in Colletotrichum lindemuthianum from South, Central, and North America

ABSTRACT Isolates of Colletotrichum lindemuthianum (138 total) from Argentina, Brazil, the Dominican Republic, Honduras, Mexico, and the United States were characterized into 41 races based on virulence to 12 differential cultivars of Phaseolus vulgaris. These 41 races were categorized into two groups: those found over a wide geographic area and those restricted to a single country. Races 7, 65, and 73 were widespread. Race 73 was the most common (28%). Race 7 was found once in Argentina and Mexico but at a higher frequency in the United States. Race 65 was found repeatedly in Brazil and the United States. Although 39% of the races were detected repeatedly and three races were widespread, no race was isolated from both P. vulgaris gene pools. Phenetic analyses showed no obvious patterns correlated with virulence clusters. No geographic pattern was evident. Molecular polymorphism generated by random amplified polymorphic DNA confirmed the extensive variability in virulence of C. lindemuthianum. Virulence phenotypes were grouped into 15 clusters. The two largest clusters contained isolates from all the geographic regions sampled. Molecular polymorphism was observed among isolates from races 65 and 73 within and among countries, except among Bra-zilian isolates of race 65. The genetic diversity of C. lindemuthianum was greatest in Mexico and Honduras. Our data suggest that C. lindemuthianum may not be highly structured to specific Phaseolus gene pools.     

The origin and genetic diversity of the causal agent of Asian soybean rust,Phakopsora pachyrhizi,in South America

A sequence‐based approach was used to investigate molecular genetic variations in Phakopsora pachyrhizi, an obligate biotrophic pathogen that causes Asian soybean rust. In Argentina, the samples came from uredinium‐bearing leaves taken from 11 soybean fields; in Brazil, the samples comprised urediniospores from leaves of 10 soybean genotypes that had been grown in three experimental stations during two growing seasons. PCR‐based cloning techniques were used to generate DNA sequences for two gene regions and alignments were supplemented with data from GenBank. A total of 575 sequences for the internal transcribed spacer region (18 ribotypes) and 160 partial sequences for a housekeeping gene encoding ADP‐ribosylation factor (10 haplotypes) were obtained. Ribotype accumulation curves predicted that about 20 bacterial clones would recover 5–6 ribotypes (c. 70–80% of the total molecular variation) per locality. The samples from the three experimental stations in Brazil displayed most (14 out of 16) ribotypes found worldwide; the lack of genetic structure and differentiation at a diverse geographic scale suggests that both local and distant sources provide airborne inoculum during disease establishment. Soybean genotypes with resistance genes for the Asian soybean rust did not decrease the molecular genetic variation of fungal populations.     

Epidemiology of sharka disease in North America

The history of North American (USA and Canada) epidemics of Plum pox virus (PPV), as well as hypotheses about the general North American epidemiology of PPV, are summarized. The hierarchical sampling method, combined with reliable DASI-ELISA detection/confirmation procedures, were successfully used for extensive PPV surveys of stonefruit-producing areas in both countries. The influence of epidemiological analyses on eradication policy is described.     

Coffee berry disease in Kenya. II. The role of Glomerella cingulata in the Colletotrichum population,colonizing the bark of Coffea arabica

On the maturing bark of cut branches ofCoffea arabica previously sprayed with copper fungicides perithecia ofGlomerella cingulata were easily found after two to ten days of incubation. Without fungicides the number of perithecia was decidedly lower. On prunings left on the ground under the coffee trees for 6 to 24 weeks the perithecia could also be found, but the numbers declined rapidly with time. Perithecia ofG. cingulata could forcibly discharge ascospores under laboratory conditions. Monospore cultures obtained by catching ascospores on agar, invariably belonged to threeColletotrichum types. It was rarely possible to isolate aColletotrichum able to infect green coffee berries. Growthrate, colour of the mycelium, number of conidia producedin vitro and infectivity on green coffee berries, however, differed substantially fromC. coffeanum, the cause of coffee berry disease. In Kenya no evidence has been obtained that ascospores from perithecia on bark could infect wounded or unwounded green coffee berries. Neither has any infection been obtained with ascospores from perithecia grownin vitro. Possible explanations for the difference with previous findings are offered. Based on the data presented in this paper, it is concluded thatG. cingulata is not likely to play a role in the epidemiology of the coffee berry disease in Kenya.     

Investigations into some aspects of the biology of potatoes as weeds

The results of a survey of potato fields have shown that up to 370 000 tubers/ha may remain in the field after the potato harvest. Most of these tubers were less than 4 cm in diameter and their distribution in the soil suggests that they had fallen between the bars of the harvester elevators. Despite high mortality during winter, substantial populations of potato plants were found in subsequent crops. Up to 50 000 sprouts/ha were recorded in a survey of several winter wheat fields. Emergence of these sprouts started in April and continued until the end of May, and in other trials new sprouts were still emerging at the end of June. Several experiments indicated that soil temperatures and moisture levels in spring and also tuber depth affected emergence; the deeper tubers emerged later. Weed potato plants in cereal crops were found to produce an average of 2 daughter tubers, thus providing a tuber population for infestations in the following year. The results are compared with those of other workers, and their importance in the development of methods of control is discussed.     

Coffee berry disease in Kenya. I. Colletotrichum spp. colonizing the bark of Coffea arabica

Several species ofColletotrichum occur in maturing bark ofCoffea arabica branches in Kenya. TheColletotrichum population inhabits the bark tissue external to the developing phellogens in the cortex. TheColletotrichum species are unable to invade green bark tissue, where the phellogen has not yet been differentiated, while colonization ceases on the phelloderm of the true bark. Only one of theColletotrichum species discussed in this paper,C. coffeanum, can infect green coffee berries. Shortly after the initiation of the first phellogen in the cortex the parasite is in a small area in the bark. It cannot be found in bark tissues where more phellogens have been formed and where the colour of the bark has changed from yellow-green to brown or black. From the bark ofC. liberica trees, grown in Kenya, andC. arabica cv. ’lsBourbon’, grown in greenhouses in the Netherlands one of the saprophytic components of theColletotrichum population could be isolated. It was impossible to induce ddie-back symptoms or mere infection by inoculation of green internodes even after wounding of live branches ofC. arabica with any of theColletotrichum components colonizing the bark. It is suggested that die-back systems of coffee in Kenya are primarily caused by unfavourable growing conditions.     

云南省玉溪市玉米致死性坏死病毒原的分子鉴定

玉米致死性坏死病是由玉米褪绿斑驳病毒(Maize chlorotic mottle virus,MCMV)和一种或多种马铃薯Y病毒科病毒复合侵染引起的。2014年1月在对云南省玉溪市玉米病毒病害的调查中发现了一些表现严重花叶、矮化叶片甚至整个植株坏死症状的玉米。对采集样品进行RT-PCR检测,所有样品中都同时检测到了MCMV和甘蔗花叶病毒(Sugarcane mosaic virus,SCMV),在一个样品中同时检测到了MCMV、SCMV和南方水稻黑条矮缩病毒(Southern rice black-streaked dwarf virus)。     

福建永安市辣椒丛枝病植原体的分子检测及鉴定

永安地区发病辣椒植株表现小叶、黄化、丛枝、簇芽等症状。利用植原体16SrDNA基因的通用引物R16mF2/R16mR2和R16F2n/R16R2,对发病辣椒植株总DNA进行巢式PCR检测,获得约1.2kb的特异性DNA片段。经测序并在GenBank数据库进行比对分析,共获得4条植原体特定的16SrDNA基因序列(CHY-C4-1、CHYY1-1、CHY-Y7-1、CHY-G1-1)。将测得的4条序列与已报道的植原体序列进行同源性比对,并构建系统进化树,结果显示获得的4条植原体序列均聚类到16SrI组,其中CHY-Y1-1、CHY-Y7-1、CHY-G1-1与16SrI-B亚组植原体聚类到同一支,而CHY-C4-1与已报道的16SrI组内的6个亚组均未聚类到一支,因此建议将CHY-C4-1命名为新的亚组。利用iPhyClassifier在线分析软件对获得的4条植原体序列进行虚拟RFLP分析,结果与进化树获得的结果一致。     

Spatial and temporal analysis of coffee wilt disease caused by Fusarium xylarioides in Coffea canephora

Coffee wilt disease (CWD) caused by Fusarium xylarioides, considered to be a soil-inhabiting fungus, is endemic in several African countries, affecting commercially important coffee species and causing serious economic losses. Coffee wilt disease development in naturally infected Coffea canephora fields at the Coffee Research Institute in Uganda was assessed from April 2001 to March 2006 to generate information about temporal and spatial spread of the disease. Maps of diseased trees were also generated from the data. Semi-variance analysis was performed on the data to show the spatio-temporal structure of disease. Host influence on the spatio-temporal structure was deduced from the distribution pattern of diseased and healthy trees and analysis of variance. Results show that the temporal disease epidemic progress was slow. The disease was found to spread from initial infections to healthy neighbouring trees, resulting in an aggregated pattern. An infected tree could infect up to three healthy trees away, in any direction. Disease foci formed and expanded with time, coalescing but punctuated in spots planted with resistant hosts. There were varying levels of susceptibility among host genotypes, affecting the rates and levels of epidemic development. The implications of the findings to the control of CWD are discussed.     

Control of benomyl-resistant strains of Colletotrichum coffeanum, the cause of coffee berry disease

Sprays containing difolatan, dithianon, chlorothalonil and cuprous oxide were tested for the control of coffee berry disease (CBD) in 1979 and 1980 at an estate in Kenya with abundant benomyl-resistant strains of Colletotrichum coffeanum. In 1979 all fungicides gave good CBD control and increased yields of coffee. In 1980 only difolatan increased yield. Isolates of C. coffeanum capable of growing on agar with 8 μg/ml benomyl were detected throughout the 2 years of these trials.     

The tomato borer Tuta absoluta in South America: pest status,management and insecticide resistance

The tomato borer Tuta absoluta (Lepidoptera: Gelechiidae) has been a recognized pest in South America since the 1960s, quickly spreading to the major tomato‐producing countries in the region. A series of studies regarding this pest's biology, ecology and management were conducted to contain tomato losses within acceptable levels. Although cultural control methods were attempted against T. absoluta, as were the development of resistant tomato varieties and the use of pheromones and natural enemies, insecticides are still the main control method used. The sex pheromone of T. absoluta was identified, confirmed and synthesized in the late 1990s and it is currently used for detection and monitoring of this species, but improved sampling plans are still necessary for its use in decision‐making regarding insecticide use. Insecticide use has shifted from earlier reliance on organophosphates, pyrethroids, cartap and abamectin to insect growth regulators and, more recently, to novel insecticides. Unfortunately, the overreliance on insecticide use led to problems with insecticide resistance in the region, which is a current matter of concern not only in South America, but also elsewhere since introduced strains may carry insecticide‐resistance genes at high frequency even without local selection in the site of introduction.