Cacao diseases: important threats to chocolate production worldwide

ABSTRACT Theobroma cacao, cacao, is an ancient, neotropical domesticate. It is now grown throughout the humid, lowland tropics and is the basis of a multibillion dollar confectionary trade. Diverse diseases impact production of the crop. They reduce yields by ca. 20%, but could cause far greater losses if certain highly damaging diseases were to become more widely distributed. Among the most potentially dangerous of these diseases are frosty pod, caused by Moniliophthora roreri, and witches' broom, caused by M. perniciosa (previously Crinipellis perniciosa). These two diseases occur only in the Western Hemisphere, and severe losses would follow their introduction to West Africa and Asia, where ca. 86% of all cacao production occurs. Elsewhere, Cacao swollen shoot virus and the damaging black pod agent, Phytophthora megakarya, are found in Western Africa; whereas vascular streak dieback, caused by Oncobasidium theobromae, is present only in Asia. Breeding programs are challenged by minimal resistance to some of the diseases. Progress that has been made is threatened by the "emergence" of other serious diseases, such as Ceratocystis wilt (Ceratocystis cacaofunesta). During this symposium, new insights are discussed on the biology, origins, pathology and phylogeny of the pathogens; as well as the biological, chemical and genetic management of the diseases that they cause.     

Natural products in agriculture—a view from the industry

The paper discusses the use of natural products and biological control agents in crop protection from an industrial viewpoint. The criteria which must be satisfied are noted. Examples are given from the genetic engineering of baculoviruses and proteins. The final section considers the utility of natural products as a source of leads for conventional agrochemicals, and the screens needed. © 1998 SCI.     

Transgenic crops: a view from the US Extension Service

This communication discusses the current situation in the USA with regard to the growing of transgenic crops, with particular reference to soybeans, corn, cotton and rice. High costs of production and low prices require and greater production efficiency and transgenic crops help to achieve this goal, particularly with soybeans, cotton and rice. Copyright © 2000 Society of Chemical Industry     

从风水的视角看唐代敦煌地区民众的人居环境观

以敦煌地区的自然生态环境为出发点,以传统风水理论作为视角,考察了唐代敦煌地区民众的人居环境观念,认为敦煌地区民众十分重视处理人、住宅和自然环境之间的关系,认为三者之间是一种互相依存,相互协调的关系,这种朴素的人居环境观念对今天该地区人居环境的营造乃至新农村建设能提供重要的借鉴。     

Intellectual property in entomology: Analysis and perspective on recent trends in global patent publications

Intellectual property (IP) is an important consideration for entomological research and provides a means to capture value from new discoveries. Herein, we describe an analysis of more than 26 000 patent publications from 2007–2017 related to the field of entomology. These patents were divided among 8000 patent assignees; however, only 5% of the assignees had ≥10 patents. Corporations accounted for the largest share of patents (59%), with individuals (20%), academic institutions (17%) and government organizations (4%) making up the remaining segments. From 2007–2017 the number of entomological patents increased by 400%, with the largest number being from China. However, unlike patents from Europe, Japan or the US, which target a range of countries, the Chinese patents almost exclusively focus on China. Among the array of subjects covered are transgenic insects and plants, repellents, recombinant insect cells, with the highest proportion of patents focused on insecticides (39%), followed by insecticide mixtures (27%) and formulations (21%). The top 30 patent assignees included companies/institutions from China (18), Europe (3), Japan (6) and the US (3). Among the top 12 entities, IP from the US assignees was distributed across insecticides, mixtures and insecticidal traits while those from China were more focused on mixtures. However, given expanding IP numbers from China it is expected that in the future there will be a greater impact on new insecticides and related technologies. © 2020 Society of Chemical Industry     

Genetic and Biological Diversity of Trichoderma stromaticum, a Mycoparasite of the Cacao Witches'-Broom Pathogen

ABSTRACT The witches'-broom disease, caused by the basidiomycete Crinipellis perniciosa, is the most limiting factor for cacao cultivation in Brazil. Trichoderma stromaticum is a mycoparasite of the witches'-broom pathogen of cacao that is currently being applied in the field to manage the disease in Bahia State, Brazil. In this work, molecular and traditional methods were used to study the genetic and biological diversity of this mycoparasite. Ninety-one isolates, mostly collected from farms not sprayed with the fungus, were analyzed by amplified fragment length polymorphisms (AFLP), which showed that two genetic groups (I and II) of T. stromaticum occur in Bahia State. This classification of T. stromaticum into two distinct AFLP groups was also in agreement with several other characteristics, including growth on agar media at different temperatures and sporulation on infected stem segments (broom pieces) and rice grains. Group II favors higher temperatures compared with group I. The genetic and biological differences of the isolates, however, were not evident in field experiments, where sporulation was evaluated on the surface of brooms under natural conditions. Our results show that there is considerable genetic and biological diversity within T. stromaticum in Bahia and other cacao-growing regions of South America that are affected by the witches'-broom disease. This diversity could be explored in the development of efficient biological control agents against the disease. Factors that may affect the application and performance of this biocontrol agent in the field, such as sporulation on rice substrate and on the brooms and growth at various temperatures, are discussed.     

Biopesticides — harmonization of registration requirements within EU Directive 91/414 — an industry view1

A range of biopesticides (including, as active substances, bacteria, viruses, fungi, nematodes, protozoa and beneficial insects) is now commercially available for control of insect pests, fungal and bacterial diseases and weeds. The term biopesticide can include pheromones, insect and plant growth regulators, plant extracts, transgenic plants and macroorganisms as well as microorganisms. However, world biopesticide sales in 1990 were estimated to be 120 million USD, representing less than 0.5% of the world's agrochemical market. Out of this, approximately 90% of the biopesticide sales are represented by the bacterium Bacillus thuringiensis for the control of insect pests. Nevertheless, biopesticide sales are estimated to be increasing at 10–25% per annum and sales by the year 2000 are estimated to reach 1000 million USD. This paper looks at the current commercial status and the constraints that are facing industry concerning changing registration, particularly in Europe, the absence of harmonized data requirements, and the increasing costs and delays in registrations that deter the development of new biopesticides.     

Plant biology and other issues that relate to the management of water hyacinth: a global perspective with focus on Europe1

Water hyacinth reproduces vegetatively and sexually and seeds are numerous and long‐lived. Rates of vegetative growth are high (weight and numbers can double in less than 1 week in optimal conditions) and governed by temperature and available nutrients. The period from germination to setting seed can be less than 12 weeks. Dispersal of propagules is by flow, man and machines. Biomass of living material is high 90 to > 800 tonnes/ha and comprises around 95% water, and the weed often grows in inaccessible areas. Consequently, social, economic and environmental impacts of water hyacinth are often large and management of the problem becomes very important. However, management of water hyacinth is difficult, and utilization of this weed should not be mistaken as a control measure. Containment and eradication from a catchment may only be accomplished if the invasion is very young, small, isolated and accessible, and if the short‐term resource commitment is high. Most infestations are non‐eradicable because once noticed reaction time is too long. However, in Europe, as the weed invades new areas on the edges of its ecological range, eradication of new infestations could (should) be attempted as this is the most cost effective way to deal with the weed. In addition, pathway shut‐down and awareness campaigns should seek to reduce further new introductions, which, for spread to new regions, are mostly anthropogenic. For established populations the removal of accessible floating biomass can be accomplished using herbicides (if permitted) and by mechanical means. Both are expensive because re‐growth ensures repeated action is necessary. Biological control is a useful tool in warmer climates, less so in cooler climates. It may be more useful in cooler areas if integrated with other management techniques. Additional biological control agents are being studied to improve and broaden the value of biological control. The lack of policies to permit the use of biological control for weeds in Europe limits the ability to manage this weed.     

Cacao resistance to Phytophthora: Effect of pathogen species, inoculation depths and pod maturity

Two species of Phytophthora (P. palmivora and P. capsici) and inoculations at two depths (3 mm and 9 mm) were tested each on 10 clones of Theobroma cacao to determine their effects on pod resistance. Ripe and unripe pods were also assessed to determine the influence of physiological status of the pod on the expression of resistance. The two pathogens tested (P. palmivora and P. capsici) differed significantly in their reactions on pods, with P. palmivora being more aggressive than P. capsici. However, the lack of interaction between clones and pathogen species and the similarity in the ranking of clones based on lesion size suggested that selection for resistant clones can be based on one of the two pathogens, preferably the more aggressive one. Pod reactions differed between inoculation depths (3 mm and 9 mm), and between pod maturity stages (ripe and unripe pods) with relatively larger lesions being recorded at 9 mm depth and on unripe pods as compared to those observed at 3 mm depth and on unripe pods, respectively. The magnitude of increase in lesion sizes, however, varied with genotypes, indicating that inoculation depth and pod maturity stage should be standardized in screening cacao germplasm for resistance to Phytophthora.     

Production and Germination of Conidia of Trichoderma stromaticum, a Mycoparasite of Crinipellis perniciosa on Cacao

ABSTRACT Growth characteristics of the fungus Trichoderma stromaticum, a mycoparasite on the mycelium and fruiting bodies of Crinipellis perniciosa, the causal agent of witches'-broom disease of cacao, were evaluated under controlled environmental conditions. The ability of T. stromaticum to produce conidia and germinate on dry brooms was evaluated at three constant temperatures (20, 25, and 30 degrees C) and two constant relative humidities (75 and 100%). T. stromaticum produced abundant conidia on brooms at 100% relative humidity and incubation temperatures of 20 and 25 degrees C, but none at 30 degrees C. Sporulation of T. stromaticum was not observed at 75% relative humidity at any temperature. At 100% relative humidity and either at 20 or 25 degrees C, treatment of brooms with T. stromaticum suppressed C. perniciosa within 7 days. In contrast, at 30 degrees C, treatment with T. stromaticum had no effect on the pathogen in brooms maintained at either 75 or 100% relative humidity. Mycelium of C. perniciosa grew from brooms at all temperatures at 100% relative humidity. Conidial germination on broom tissue approximated 80% at temperatures from 20 to 30 degrees C. Results suggest that applying T. stromaticum under high-moisture conditions when the air temperature is below 30 degrees C may enhance the establishment of this mycoparasite in cacao plantations.     

Distribution of a chemical following its application at a point source in an irrigation system

The development of large complex irrigation systems presents problems of pest control which are likely to become increasingly difficult to solve by established application methods. By applying a chemical at one point in such a system use can be made of the flow of water through the system to effect the necessary distribution. This technique has been used most effectively with the molluscicide Frescon (N-tritylmorpholine). However, the complexity of many irrigation systems precludes the optimisation of the necessary rate of addition of molluscicide by any simple method. In this paper a mathematical model of an irrigation system is described which enables a detailed study of this type of application to be made with speed and economy. An analogue computer has been used to solve the equations subject to the operating conditions of the irrigation system.     

历史时期东北地区农业系统的发展动因研究

作为不断进化的开放系统,农业系统具有较强的内在有机性和外部关联性。依据东北农业系统发展的阶段性特征,可将其演化进程划分为如下四个阶段:渔猎系统同采集系统的分化阶段,农牧系统同渔猎系统的分化阶段,农牧渔猎长期共存互补阶段以及农耕系统同畜牧系统的分化阶段。在每个发展阶段,农业系统的结构形式和功能表现均有所不同。驱动东北农业系统不断发展演化的因素有:生态制约与气候扰动,战争灾荒与农牧政策,人口迁徙与经济转型,文化互动与技术传播,宗教信仰与饮食习俗,交通条件与市场交换等。     

The impact of global warming on plant diseases and insect vectors in Sweden

Cold winters and geographic isolation have hitherto protected the Nordic countries from many plant pathogens and insect pests, leading to a comparatively low input of pesticides. The changing climate is projected to lead to a greater rise in temperature in this region, compared to the global mean. In Scandinavia, a milder and more humid climate implies extended growing seasons and possibilities to introduce new crops, but also opportunities for crop pests and pathogens to thrive in the absence of long cold periods. Increased temperatures, changed precipitation patterns and new cultivation practices may lead to a dramatic change in crop health. Examples of diseases and insect pest problems predicted to increase in incidence and severity due to global warming are discussed.     

Ensuring validation in diagnostic testing is fit for purpose: a view from the plant virology laboratory

Plant diagnostic laboratories are facing increasing demands for accreditation of their testing activities from both private and public organizations. For diagnostics, validating tests for the intended use is one of the key elements of accreditation. Thus far, validation has mainly focused on tests with a fixed scope, i.e. a test for organism X in matrix Y by method Z, suitable for the analysis of targeted samples. In many laboratories, however, targeted samples only form a minority of the samples. The majority consists of symptomatic (non‐targeted) samples including a huge variety of pest, host and matrix combinations. Since it is impossible to validate all tests used for the analysis of these non‐targeted samples, ensuring the reliability of the final results needs a different approach. This paper describes such an approach for diagnostic testing in plant virology, where the extent of validation of a test is determined based on the risks of a false result within the context of the diagnostic process. Examples illustrate how this risk‐based system approach relies on a tight inter‐relationship of validation, expertise and quality assurance within the diagnostic laboratory.     

Control of plant diseases by natural products: Allicin from garlic as a case study

This review aims to increase awareness of the potential for developing plant protection strategies based on natural products. Selected examples of commercial successes are given and recent data from our own laboratory using allicin from garlic are presented. The volatile antimicrobial substance allicin (diallylthiosulphinate) is produced in garlic when the tissues are damaged and the substrate alliin (S-allyl-l-cysteine sulphoxide) mixes with the enzyme alliin-lyase (E.C.4.4.1.4). Allicin is readily membrane-permeable and undergoes thiol-disulphide exchange reactions with free thiol groups in proteins. It is thought that these properties are the basis of its antimicrobial action. We tested the effectiveness of garlic juice against a range of plant pathogenic bacteria, fungi and oomycetes in vitro. Allicin effectively controlled seed-borne Alternaria spp. in carrot, Phytophthora leaf blight of tomato and tuber blight of potato as well as Magnaporthe on rice and downy mildew of Arabidopsis. In Arabidopsis the reduction in disease was apparently due to a direct action against the pathogen since no accumulation of salicylic acid (a marker for systemic acquired resistance, SAR) was observed after treatment with garlic extract. We see a potential for developing preparations from garlic for use in organic farming, e.g. for reducing the pathogen inoculum potential in planting material such as seeds and tubers. We have tested various encapsulation formulations in comparison to direct treatment. Note added in proof: The complete chemical synthesis of azadirachtin has now been achieved. Nature (2007) 448: 630–631     

Control of foliar diseases in barley: towards an integrated approach

Barley is one of the world??s most important crops providing food and related products for millions of people. Diseases continue to pose a serious threat to barley production, despite the use of fungicides and resistant varieties, highlighting the impact of fungicide resistance and the breakdown of host plant resistance on the efficacy of control measures. This paper reviews progress towards an integrated approach for disease management in barley in which new methods may be combined with existing measures to improve the efficacy of control in the long-term. Advances have been made in genetic mapping of resistance (R) genes and in identifying novel sources of genes in wild barley populations and land races. Marker assisted selection techniques are being used to pyramid R genes to increase the durability of resistance. Elicitors to induce host resistance used in combination with fungicides can provide effective disease control in the field and could delay the evolution of fungicide insensitivity. Traits that may contribute to disease tolerance and escape have been identified and the extent of genetic variation within barley germplasm is being determined. Tools are being developed to integrate the above methods via an assessment of the risk of economic injury occurring from disease to guide decisions on the requirement for fungicide treatment. Barriers exist to the adoption of integrated management approaches from growers and end-users further down the supply chain (e.g. acceptance of variety mixtures) and policy incentives from government may be required for it to be taken up in practice.     

Potato diseases caused by soft rot erwinias: an overview of pathogenesis

Three soft rot erwinias, Erwinia carotovora ssp. carotovora , E. carotovora ssp. atroseptica and E. chrysanthemi are associated with potatoes causing tuber soft rot and blackleg (stem rot). Latent infection of tubers and stems is widespread. As opportunistic pathogens, the bacteria tend to cause disease when potato resistance is impaired. Pathogenesis or disease development in potato tubers and stems is discussed in terms of the interaction between pathogen, host and environment, microbial competition and recent findings on the molecular basis of pathogenicity. Emphasis is placed on the role of free water and anaerobiosis in weakening tuber resistance and in providing nutrient for erwinias to multiply. Blackleg symptoms are expressed when erwinias predominate in rotting mother tubers, invade the stems and multiply in xylem vessels under favourable weather conditions. Soft rot erwinias tend to out-compete other bacteria in tuber rots because of their ability to produce larger quantities of a wider range of cell wall-degrading enzymes. However, despite extensive studies on their induction, regulation and secretion, little is known about the precise role of the different enzymes in pathogenesis. The putative role of quorum-sensing regulation of these enzymes in disease development is evaluated. The role certain pathogenicity-related characters, including motility, adhesion, siderophores, detoxifying systems and the hrp gene complex, common to most bacteria including symbionts and saprophytes, could play in latent and active infections is also discussed.     

Altered pesticide use on transgenic crops and the associated general impact from an environmental perspective

The large-scale commercial cultivation of transgenic crops has undergone a steady increase since their introduction 10 years ago. Most of these crops bear introduced traits that are of agronomic importance, such as herbicide or insect resistance. These traits are likely to impact upon the use of pesticides on these crops, as well as the pesticide market as a whole. Organizations like USDA-ERS and NCFAP monitor the changes in crop pest management associated with the adoption of transgenic crops. As part of an IUPAC project on this topic, recent data are reviewed regarding the alterations in pesticide use that have been observed in practice. Most results indicate a decrease in the amounts of active ingredients applied to transgenic crops compared with conventional crops. In addition, a generic environmental indicator -- the environmental impact quotient (EIQ) -- has been applied by these authors and others to estimate the environmental consequences of the altered pesticide use on transgenic crops. The results show that the predicted environmental impact decreases in transgenic crops. With the advent of new types of agronomic trait and crops that have been genetically modified, it is useful to take also their potential environmental impacts into account.