Review on Concepts in Biological Control of Plant Pathogens

Biological disease control is an attractive alternative strategy for the control of plant diseases. Meanwhile, it also provides practices compatible with the goal of a sustainable agricultural system. Understanding the mechanisms of biological control of plant diseases through the interactions between antagonists and pathogens may allow us to select and construct the more effective biocontrol agents and to manipulate the soil environment to create a conducive condition for successful biocontrol. Many factors have to be considered in deciding whether a biological system is feasible for the control of a particular pathogen. Of prime importance is the availability of a suitable antagonist capable of maintaining itself on the host plant. The environment under which the crop is grown will play a significant part in determining whether effective population levels of an antagonist can be established in competition with the existing microflora. Environment may also govern the choice of antagonist; for example, yeasts can survive on leaves more readily than non-spore-forming bacteria under adverse humidity conditions. It is essential that the primary mechanism by which antagonism is brought about should be known. A variety of biological controls are available for use, but further development and effective adoption will require a greater understanding of the complex interactions among plants, people and the environment. With people turning more health conscious Biological control seem to the best alternative to disease suppression. Bio-agents bring the disease suppression with no environmental hazards. Research has proved that the bio agents trigger the growth of plants. Bio agents themselves being non-pathogenic to plants need to be formulated in a way that favours the activity and survival of microbe it contains. Moreover, the organism that suppresses the pathogen is referred to as the biological control agent (BCA). More broadly, the term biological control also has been applied to the use of the natural products extracted or fermented from various sources. These formulations may be very simple mixtures of natural ingredients with specific activities or complex mixtures with multiple effects on the host as well as the target pest or pathogen. And, while such inputs may mimic the activities of living organisms, non-living inputs should more properly be referred to as biopesticides or biofertilizers, depending on the primary benefit provided to the host plant. Over the past few years, the novel applications of molecular techniques have broadened our insight into the basis of biological control of plant diseases. New molecular approaches have been available for assessment of interaction between the antagonist and pathogen, ecological traits of antagonists in rhizosphere and improving the efficacy of bacterial, fungal and viral biocontrol agent. Currently, biological control will thus be an alternative strategy for the control of plant diseases given the history of fungicides in the near future. However, other methods in IPM for crop disease control are still necessary in various environmental conditions, because an agro-ecosystem is a variable and functioning system that includes several factors that influence disease and crop development. Consequently, for economic threshold, other control strategies of IPM besides biological control should be also considered and applied to effectively reduce the disease development and the yield loss of crops in the different crop systems. Keywords: Biocontrol, biofumigation, microbial antagonism, natural compounds, pathogen

Optimal Multiphase Investment Strategies for Influencing Opinions in a Social Network

We study the problem of optimally investing in nodes of a social network in a competitive setting, where two camps aim to maximize adoption of their opinions by the population. In particular, we consider the possibility of campaigning in multiple phases, where the final opinion of a node in a phase acts as its initial biased opinion for the following phase. Using an extension of the popular DeGroot-Friedkin model, we formulate the utility functions of the camps, and show that they involve what can be interpreted as multiphase Katz centrality. Focusing on two phases, we analytically derive Nash equilibrium investment strategies, and the extent of loss that a camp would incur if it acted myopically. Our simulation study affirms that nodes attributing higher weightage to initial biases necessitate higher investment in the first phase, so as to influence these biases for the terminal phase. We then study the setting in which a camp's influence on a node depends on its initial bias. For single camp, we present a polynomial time algorithm for determining an optimal way to split the budget between the two phases. For competing camps, we show the existence of Nash equilibria under reasonable assumptions, and that they can be computed in polynomial time

Social contagions on interdependent lattice networks

Although an increasing amount of research is being done on the dynamical processes on interdependent spatial networks, knowledge of how interdependent spatial networks influence the dynamics of social contagion in them is sparse. Here we present a novel non-Markovian social contagion model on interdependent spatial networks composed of two identical two-dimensional lattices. We compare the dynamics of social contagion on networks with different fractions of dependency links and find that the density of final recovered nodes increases as the number of dependency links is increased. We use a finite-size analysis method to identify the type of phase transition in the giant connected components (GCC) of the final adopted nodes and find that as we increase the fraction of dependency links, the phase transition switches from second-order to first-order. In strong interdependent spatial networks with abundant dependency links, increasing the fraction of initial adopted nodes can induce the switch from a first-order to second-order phase transition associated with social contagion dynamics. In networks with a small number of dependency links, the phase transition remains second-order. In addition, both the second-order and first-order phase transition points can be decreased by increasing the fraction of dependency links or the number of initially-adopted nodes.This work was partially supported by National Natural Science Foundation of China (Grant Nos 61501358, 61673085), and the Fundamental Research Funds for the Central Universities. (61501358 - National Natural Science Foundation of China; 61673085 - National Natural Science Foundation of China; Fundamental Research Funds for the Central Universities)Published versio

When viruses play team sports : mixed infections in plants

Altres ajuts: Generalitat de Catalunya/CERCA ProgrammeThe pathological importance of mixed viral infections in plants might be underestimated except for a few well-characterized synergistic combinations in certain crops. Considering that the host ranges of many viruses often overlap and that most plant species can be infected by several unrelated viruses, it is not surprising to find more than one virus simultaneously in the same plant. Furthermore, dispersal of the majority of plant viruses relies on efficient transmission mechanisms mediated by vector organisms, mainly but not exclusively insects, which can contribute to the occurrence of multiple infections in the same plant. Recent work using different experimental approaches has shown that mixed viral infections can be remarkably frequent, up to the point that they could be considered the rule more than the exception. The purpose of this review is to describe the impact of multiple infections not only on the participating viruses themselves but also on their vectors and on the common host. From this standpoint, mixed infections arise as complex events that involve several cross-interacting players, and they consequently require a more general perspective than the analysis of single-virus/single-host approaches for a full understanding of their relevance

Social media in marketing research : Theoretical bases, methodological aspects, and thematic focus

The widespread use of social media as a marketing tool during the last decade has been responsible for attracting a significant volume of academic research, which, however, can be described as highly fragmented to yield clear directions and insights. We systematically synthesize and critically evaluate extant knowledge of social media marketing extracted from 418 articles published during the period 2009–2021. In doing so, we use an organizing framework focusing on five key areas of social media marketing research, namely, social media as a promotion and selling outlet, social media as a communication and branding channel, social media as a monitoring and intelligence source, social media as a customer relationship management and value cocreation platform, and social media as a general marketing and strategic tool. Within each of these areas, we provide important theoretical, methodological, and thematic insights, as well as future research directions. We also offer useful managerial implications derived from the articles reviewed.© 2022 The Authors. Psychology & Marketing published by Wiley Periodicals LLC. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.fi=vertaisarvioitu|en=peerReviewed

Advent of Trichoderma as a bio-control agent- A review

Trichoderma spp are free living filamentous fungi. They are cosmopolitan and versatile in nature. They have the potential to produce several enzymes that can degrade the cell wall materials. Also, they release a number of fungi toxic substances that can inhibit the growth of the fungal pathogens. Many mechanisms have been described on how Trichoderma exert beneficial effects on plants as a bio-control agent. But due to its versatile nature, its potential cannot be explored to its full extent. And it is a developing science in the field of bio-control with its new discoveries adding to the usefulness of the fungi as a bio-control agent. Its development as a bio-control agent passes through many phases and each phase adding novel ideas that will help in the development of an efficient bio-agent which in turn will help in the crop improvement and disease management. The studies on their various aspects responsible for bio-control will open a flood gate to the development of Trichoderma as an efficient and reliable bio-agent and provide a better scope for implementation in crop and disease management. The in vitro antagonistic activity of Trichoderma viride against phytopathogens (Sclerotium rolfsii, Fusarium oxysporum f.s.p. ciceri, Fusarium oxysporum f.s.p. udum) was studied and it was found to be potentially effective against F. oxysporum f.s.p. ciceri followed by F. oxysporum f.s.p. udum and Sclerotium rolfsii