Aerobiology in plant protection

Summary The control of phytopathogenic fungi in agriculture requires sometimes excessive chemical treatments because, in many cases, reliable monitoring systems in order to assess the real risk for the cultivations are not available.Therefore, the likelihood to assess the presence and the amount of phytophatogenic fungus propagules in the air with a spore-trap has been investigated in order to evaluate their correlation with the climate and the disease occurrence. Four phytopathogenic fungi, namelyVenturia inequalis, Phytophthora infestans, Cercospora beticola andDiaporthe phaseolorum var.caulivora were taken into consideration.Practical use of airborne spore monitoring in a disease control strategy proved to be useful only forVenturia inequalis andPhytophthora infestans causal agent of apple scab and tomato late blight respectively. For the latter, the utilisation of an aerobiological monitoring system for the disease prediction can be assumed.     

Biological plant protection

Breeding of high-yielding varieties of cultivated plants has led to spectacular results in the past 30 years. Since the genetically fixed yield potential has been exhausted to a very large extent, it is necessary to take intensive plant protection measures in addition to ensuring high nutrient supply. Plant protection has made a highly recognized contribution to the impresssive development of yields in the last few decades.     

Inherited biotic protection in a neotropical pioneer plant

Chelonanthus alatus is a bat-pollinated, pioneer Gentianaceae that clusters in patches where still-standing, dried-out stems are interspersed among live individuals. Flowers bear circum-floral nectaries (CFNs) that are attractive to ants, and seed dispersal is both barochorous and anemochorous. Although, in this study, live individuals never sheltered ant colonies, dried-out hollow stems--that can remain standing for 2 years--did. Workers from species nesting in dried-out stems as well as from ground-nesting species exploited the CFNs of live C. alatus individuals in the same patches during the daytime, but were absent at night (when bat pollination occurs) on 60.5% of the plants. By visiting the CFNs, the ants indirectly protect the flowers--but not the plant foliage--from herbivorous insects. We show that this protection is provided mostly by species nesting in dried-out stems, predominantly Pseudomyrmex gracilis. That dried-out stems remain standing for years and are regularly replaced results in an opportunistic, but stable association where colonies are sheltered by one generation of dead C. alatus while the live individuals nearby, belonging to the next generation, provide them with nectar; in turn, the ants protect their flowers from herbivores. We suggest that the investment in wood by C. alatus individuals permitting still-standing, dried-out stems to shelter ant colonies constitutes an extended phenotype because foraging workers protect the flowers of live individuals in the same patch. Also, through this process these dried-out stems indirectly favor the reproduction (and so the fitness) of the next generation including both their own offspring and that of their siblings, all adding up to a potential case of inclusive fitness in plants.     

昆虫几丁质酶及其在植物保护中的应用

本文从生理学、生物化学和分子生物学３个方面综述了昆虫几丁质酶的研究进展,并概述了它在害虫防治、主要是在抗虫育种中作为重要的基因源中的应用。e     

Intellectual property protection of plant biotechnology inventions

The intellectual property protection of biotechnology-related subject matter is undergoing significant change and several countries have revised their legislation and/or patent practice as a result of challenges from industry and members of the public. Plant-related subject matter can be protected using plant variety protection, utility patents or, in the USA, by plant patent. Although easier to obtain than a utility patent, plant variety protection does not provide the same scope of protection. Protecting a plant using a utility patent is permitted only in countries that allow the patenting of higher life forms and requires a higher degree of experimental support than is required for plant variety protection, although the scope of protection is being steadily reduced.     

Design of self-processing antimicrobial peptides for plant protection

Small antimicrobial peptides are excellent candidates for inclusion in self-processing proteins that could be used to confer pathogen resistance in transgenic plants. Antimicrobial peptides as small as 22 amino acids in length have been designed to incorporate the residual amino acids left from protein processing by the tobacco etch virus'(TEVs') NIa protease. Also, by minimizing the length of these peptides and the number of highly hydrophobic residues, haemolytic activity was reduced without affecting the peptide's antimicrobial activity.     

A history of plant virology. Cross protection

Cross protection is a type of induced resistance developing in plants against viruses. Its basis is that prior infection with one virus affords protection against closely related ones. Its history started about seventy years ago, when the Dutchman Thung and the Englishman Salaman described the phenomenon independently. During the 1930s, several virologists confirmed the discovery, which was considered the first possibility to protect plants against virus infection. Growing interest also led plant virologists to formulate the first hypotheses on its mechanism, with the onset of a still unsolved debate. The hypotheses, that have been succeeded until the 1970s, included (i) antibody formation, (ii) exhaustion of essential metabolites, (iii) limited sites for virus multiplication, and (iv) specific adsorption by new cell compounds. These hypotheses were re-proposed and discussed on several occasions without arriving at a final conclusion. The statement of molecular genetics of viruses produced new interesting "theories", fundamentally based on the interference between virus strains. A model developed by the Americans Palukaitis and Zaitlin in 1984 indicates that excess of progeny positive-sense RNA of the protecting strain would sequester the minus-strand RNA of the challenging strain. Other models involve a function of the coat protein, or gene recombination. However, no model that could unify all the various facets of cross protection has hitherto been proposed. All that has not stopped the phenomenon having practical application. From the first attempts against a severe disease of cocoa in West Africa realized by Posnette in the 1940s, a number of crops (such as tomato, tobacco, citrus, cucurbits, grapevine, soybean, papaya, and so on) have been submitted to this practice. During the 1980s, cross protection came to a standstill because of the development of new resistant or tolerant cultivars. Its story is by no means ended, and much work is needed to understand its limits and possibilities.     

Mass production of entomopathogenic nematodes for plant protection

Entomopathogenic nematodes of the genera Heterorhabditis and Steinernema are commercially used to control pest insects. They are symbiotically associated with bacteria of the genera Photorhabdus and Xenorhabdus, respectively, which are the major food source for the nematodes. The biology of the nematode-bacterium complex is described, a historical review of the development of in vitro cultivation techniques is given and the current use in agriculture is summarised. Cultures of the complex are pre-incubated with the symbiotic bacteria before the nematodes are inoculated. Whereas the inoculum preparation and preservation of bacterial stocks follow standard rules, nematodes need special treatment. Media development is mainly directed towards cost reduction, as the bacteria are able to metabolise a variety of protein sources to provide optimal conditions for nematode reproduction. The process technology is described, discussing the influence of bioreactor design and process parameters required to obtain high nematode yields. As two organisms are grown in one vessel and one of them is a multicellular organism, the population dynamics and symbiotic interactions need to be understood in order to improve process management. Major problems can originate from the delayed or slow development of the nematode inoculum and from phase variants of the symbiotic bacteria that have negative effects on nematode development and reproduction. Recent scientific progress has helped to understand the biological and technical parameters that influence the process, thus enabling transfer to an industrial scale. As a consequence, costs for nematode-based products could be significantly reduced.     

Application of organic acids for plant protection against phytopathogens

The basic tendency in the field of plant protection concerns with reducing the use of pesticides and their replacement by environmentally acceptable biological preparations. The most promising approach to plant protection is application of microbial metabolites. In the last years, bactericidal, fungicidal, and nematodocidal activities were revealed for citric, succinic, α-ketoglutaric, palmitoleic, and other organic acids. It was shown that application of carboxylic acids resulted in acceleration of plant development and the yield increase. Of special interest is the use of arachidonic acid in very low concentrations as an inductor (elicitor) of protective functions in plants. The bottleneck in practical applications of these simple, nontoxic, and moderately priced preparations is the absence of industrial production of the mentioned organic acids of required quality since even small contaminations of synthetic preparations decrease their quality and make them dangerous for ecology and toxic for plants, animals, and human. This review gives a general conception on the use of organic acids for plant protection against the most dangerous pathogens and pests, as well as focuses on microbiological processes for production of these microbial metabolites of high quality from available, inexpensive, and renewable substrates.

     

Cereal production,crop protection and plant breeding*

Trends in British agriculture which have led to the eclipse of rotations, to the concentration of cereal production on wheat and barley, and to a changeover to winter cereals, have increased the vulnerability of cereal crops to disease. Epidemics have been prevented by the deployment of effective resistances and, more recently, of a wide range of crop protection chemicals. Ecological protection by means of variety mixtures and field diversification has now added a new and effective element for the defence of cereals. The problem of durability of resistances and of the continuing effectiveness of chemicals remains, and new problems of susceptibility of crop varieties to herbicides have arisen. It is possible through the combined use of genetical, chemical and ecological defence mechanisms, to maximise the period of effectiveness of resistance genes and of fungicides and insecticides. The experience of the past half-century has shown that dependence on a single protective mechanism provides only a transient solution to controlling disease.     

Contribution of cell and molecular biology and genetics to plant protection

Plants resist to the majority of their potential aggressors by opposing physical and chemical barriers: cell walls, secondary metabolites.... Phenomena of specific recognition between a plant variety and a pathovar induce on the one hand, a local (hypersensitive) reaction that tends to limit pathogen growth and, on the other hand, a cascade of signals that allows the activation of a non-specific general (systemic) resistance. The contribution of genetics to the fight against pathogens depends on the natural variability that comes from the co-evolution between plants and their aggressors. Many plant varieties resistant to one or several pathogens have been obtained and are cultivated. The use of biotechnology will facilitate the rapid generation of new, resistant cultivars and cultivars with multiple resistances. New methods in order to increase the efficiency and the durability of resistance are envisaged.     

The role of proteolytic enzymes and their inhibitors in plant protection (review)

Literature data on possible ways of involvement of proteolytic enzymes and their inhibitors in protection of plants from pests and diseases are analyzed. Certain practical applications of natural protease inhibitors to plant protection are discussed.     

Mitochondrial calcium transport and permeability transition as rational targets for plant protection

The mitochondrial permeability transition (MPT) is a death-inducing mechanism that collapses electrochemical gradients across inner mitochondrial membranes. Several studies in model plants have detailed potential MPT-dependent cell death upon abiotic stress in response to heat shock, ultraviolet radiation, heavy metal toxicity and waterlogging. However, the molecular specifics of the MPT and its possible role on plant cell death remain controversial. This review addresses previous and recent developments on the role(s) of the MPT in plants. Considering these advances, MPT targeting can constitute a plausible strategy to ameliorate cell death in plants upon abiotic stress.