Decoding Late Blight of Potato and Tomato: Insights into Pathogen Dynamics, Host Interactions and Emerging Solutions

Competition between organisms interfere in host and pathogen dynamics in ways that are difficult to predict. By one side, competitors can reduce the food supply and cause nutritional stress. Such stress could further modulate the susceptibility to infection by altering immune response or metabolic rate of the host. Alternatively, competitors may trap pathogens before they reach the focal host, and therefore reduce, enhance, or have no effect on infection according to the competitor's susceptibility to the infection. To better understand how competition influences host and pathogen interactions, we experimentally assessed the relative importance of competition for pathogens and resources on the severity of a viral disease infecting the Pacific oysterCrassostrea gigas. We designed an open‐flow system where food enriched seawater flowed to filter‐feeding competitors (or empty controls) before being delivered to recipient oysters. We tested a range of competing species that exhibit both low (ascidians, European oysters, mussels) and high (Pacific oysters) susceptibility to the virus. We assessed the physiological condition of the recipient oysters during acclimation, we added virus‐contaminated seawater upstream of the distribution system, and we monitored host and pathogen dynamics. We found that the presence of competitors, regardless of susceptibility to the virus, indirectly reduced the infection rate of hosts by decreasing their food ingestion and growth rates. Although competitors can reduce viral particles from the seawater, this had no effect on the host population. Our data suggest that the effect of competition for food overwhelmed that of competition for pathogens, thus emphasizing the importance of considering resource availability in host and pathogen dynamics. More particularly, resource availability can have positive effects at the individual level, fostering physiological condition and growth, but negative effects at the population level, increasing magnitude of epidemics.

This review investigates Rhizoctonia species, highlighting their taxonomy, genetic diversity, and pathogenic mechanisms that pose significant challenges to agriculture and horticulture. Rhizoctonia spp. are complex pathogens capable of infecting a wide range of hosts through sophisticated infection strategies and developing resistance to commonly used fungicides, threatening global food security. Key findings reveal the necessity of integrated disease management strategies that combine cultural practices, biological control, chemical applications, and the deployment of resistant cultivars to manage these pathogens effectively. The review also emphasizes the growing impact of climate change on pathogen dynamics and disease prevalence, stressing the need for flexible and innovative management approaches. A multidisciplinary approach, integrating insights from plant pathology, genetics, soil science, and climate science, is essential to address Rhizoctonia-related diseases comprehensively. This strategy not only aims to reduce the immediate impact of Rhizoctonia on crop health and yield but also enhances the long-term sustainability and resilience of agricultural and horticultural systems amid evolving environmental conditions, contributing to global efforts in maintaining food security.

The dynamics of directly transmitted pathogens in natural populations are likely to result from the combined effects of host traits, pathogen biology, and interactions among pathogens within a host. Discovering how these factors work in concert to shape variation in pathogen dynamics in natural host-multi-pathogen systems is fundamental to understanding population health. Here, we describe temporal variation in incidence and then elucidate the effect of hosts trait, season and pathogen co-occurrence on host infection risk using one of the most comprehensive studies of co-infection in a wild population: a suite of seven directly transmitted viral and bacterial respiratory infections from a 4-year study of 200 free-ranging African buffalo Syncerus caffer. Incidence of upper respiratory infections was common throughout the study-five out of the seven pathogens appeared to be consistently circulating throughout our study population. One pathogen exhibited clear outbreak dynamics in our final study year and another was rarely detected. Co-infection was also common in this system: The strongest indicator of pathogen occurrence for respiratory viruses was in fact the presence of other viral respiratory infections. Host traits had minimal effects on odds of pathogen occurrence but did modify pathogen-pathogen associations. In contrast, only season predicted bacterial pathogen occurrence. Though a combination of environmental, behavioural, and physiological factors work together to shape disease dynamics, we found pathogen associations best determined infection risk. Our study demonstrates that, in the absence of very fine-scale data, the intricate changes among these factors are best represented by co-infection.

Lysosome disruption associated with hypersensitive reaction in the potato- Phytophthora infestans host-parasite interaction

Chapter 14 - Forecasting Diseases and Insect Pests for a Value-Added Agroadvisory System

[This retracts the article DOI: 10.1007/s12298-012-0157-z.].

The oomycete, Phytophthora infestans, is one of the most important plant pathogens worldwide. Much of the pathogenic success of P. infestans, the potato late blight agent, relies on its ability to generate large amounts of sporangia from mycelia, which release zoospores that encyst and form infection structures. Until recently, little was known about the molecular basis of oomycete pathogenicity by the avirulence molecules that are perceived by host defenses. To understand the molecular mechanisms interplay in the pathogen and host interactions, knowledge of the genome structure was most important, which is available now after genome sequencing. The mechanism of biotrophic interaction between potato and P. infestans could be determined by understanding the effector biology of the pathogen, which is until now poorly understood. The recent availability of oomycete genome will help in understanding of the signal transduction pathways followed by apoplastic and cytoplasmic effectors for translocation into host cell. Finally based on genomics, novel strategies could be developed for effective management of the crop losses due to the late blight disease.

In Europe, two fastidious phloem-limited pathogens, 'Candidatus Phytoplasma solani' (16SrXII-A) and 'Candidatus Arsenophonus phytopathogenicus', are associated with rubbery taproot disease (RTD) and syndrome basses richesses (SBR) of sugar beet, respectively. Both diseases can significantly reduce yield, especially when accompanied by root rot fungi. This study investigates the presence, geographic distribution and genetic traits of fastidious pathogens and the accompanying fungus, Macrophomina phaseolina, found on sugar beet across four geographically separated plains spanning seven countries in Central Europe. The survey revealed variable incidences of symptoms linked to these fastidious pathogens in the Pannonian and Wallachian Plains, sporadic occurrence in the North European Plain, and no symptomatic sugar beet in the Bohemian Plain. Molecular analyses unveiled the occurrence of both 'Ca. P. solani' and 'Ca. A. phytopathogenicus' throughout Central Europe, with a predominance of the phytoplasma. These fastidious pathogens were detected in all six countries surveyed within the Pannonian and Wallachian Plains, with only a limited presence of various phytoplasmas was found in the North European Plain, while no fastidious pathogens were detected in Bohemia, aligning with observed symptoms. While 16S rDNA sequences of 'Ca. P. solani' remained highly conserved, multi-locus characterization of two more variable loci (tuf and stamp) unveiled distinct variability patterns across the plains. Notably, the surprising lack of variability of tuf and stamp loci within Central Europe, particularly the Pannonian Plain, contrasted their high variability in Eastern and Western Europe, corresponding to epidemic and sporadic occurrence, respectively. The current study provides valuable insights into the genetic dynamics of 'Ca. P. solani' in Central Europe, and novel findings of the presence of 'Ca. A. phytopathogenicus' in five countries (Slovakia, Czech Republic, Austria, Serbia, and Romania) and M. phaseolina in sugar beet in Slovakia. These findings emphasize the need for further investigation of vector-pathogen(s)-plant host interactions and ecological drivers of disease outbreaks.

Understanding the dynamics of multihost pathogens, such as Mycobacterium tuberculosis complex (MTC), requires considering not only host interaction patterns but also variation in infectiousness across species. Network analysis is a useful tool to assess contact structure and disease risk, but it often depends on invasive methods. Camera trapping offers a noninvasive alternative to build co‐occurrence networks in complex communities. In this study, we applied a novel approach that integrates shedding into ecological networks, weighing links between species pairs according to their co‐occurrence frequency and shedding capacity, to evaluate tuberculosis (TB) risk across 18 study sites in the Iberian Peninsula. At the community level, TB risk was positively associated with mean strength‐out, a local centrality measure of the frequency of interspecific contacts and their infectious potential. Species‐specific models revealed that community TB risk increased with the strength‐out of wild boar, red deer, and cattle, and with the closeness of red fox and badger. Furthermore, the community TB risk was jointly explained by shedding‐weighted connectivity and spatial aggregation of wild boar, whereas red deer mainly contributed through their local abundance. In contrast, shedding‐weighted centrality of badgers, foxes, and cattle explained TB risk, suggesting that ecological and management factors may influence TB spread. We defined epidemiological scenarios according to latitude, population factors, and infection pressure. These findings highlight the importance of including host infectiousness in ecological network analyses, as well as combining centrality measures and population data to understand and manage TB risk in complex host communities, with potential applications to other wildlife diseases and multihost systems.

Pathogen and human host interaction dynamics are often more complicated in the presence of co-pathogens. Co-infection can occur either as the presence of pre-existing pathogen which is accelerated by the new pathogen and more complications happened. In this study, we look at the burden of HIV/HCV viremia and the efficacy of treatment in reducing the severity of HIV/HCV co-infection patterns. Disease-free equilibrium and endemic equilibrium are two equilibrium states determined in the absence of drugs. The basic reproduction number is computed and the stability of the disease-free equilibrium of the model is analyzed using it. Here we have also incorporated the optimal drug therapy to control the co-infection disease progression. The efficacy of treatment has also been found to influence the natural progression of HCV in HIV/HCV co-infection. The numerical results suggest that the HIV viral load impacts the severity of the HCV infection impressively. This research is significant to develop antiviral therapy strategies to control HIV/HCV co-infection. The most effective way to control the co-infection with the minimum side effects is to take the combination of three medications with optimal dosing.

absent

BackgroundPlant-pathogenic oomycetes are responsible for economically important losses in crops worldwide. Phytophthora palmivora, a tropical relative of the potato late blight pathogen, causes rotting diseases in many tropical crops including papaya, cocoa, oil palm, black pepper, rubber, coconut, durian, mango, cassava and citrus.Transcriptomics have helped to identify repertoires of host-translocated microbial effector proteins which counteract defenses and reprogram the host in support of infection. As such, these studies have helped in understanding how pathogens cause diseases. Despite the importance of P. palmivora diseases, genetic resources to allow for disease resistance breeding and identification of microbial effectors are scarce.ResultsWe employed the model plant Nicotiana benthamiana to study the P. palmivora root infections at the cellular and molecular levels. Time-resolved dual transcriptomics revealed different pathogen and host transcriptome dynamics. De novo assembly of P. palmivora transcriptome and semi-automated prediction and annotation of the secretome enabled robust identification of conserved infection-promoting effectors. We show that one of them, REX3, suppresses plant secretion processes. In a survey for early transcriptionally activated plant genes we identified a N. benthamiana gene specifically induced at infected root tips that encodes a peptide with danger-associated molecular features.ConclusionsThese results constitute a major advance in our understanding of P. palmivora diseases and establish extensive resources for P. palmivora pathogenomics, effector-aided resistance breeding and the generation of induced resistance to Phytophthora root infections. Furthermore, our approach to find infection-relevant secreted genes is transferable to other pathogen-host interactions and not restricted to plants.

In this review, we explore how ecological concepts may help assist with applying microbial biocontrol agents to oomycete pathogens. Oomycetes cause a variety of agricultural diseases, including potato late blight, apple replant diseases, and downy mildew of grapevine, which also can lead to significant economic damage in their respective crops. The use of microbial biocontrol agents is increasingly gaining interest due to pressure from governments and society to reduce chemical plant protection products. The success of a biocontrol agent is dependent on many ecological processes, including the establishment on the host, persistence in the environment, and expression of traits that may be dependent on the microbiome. This review examines recent literature and trends in research that incorporate ecological aspects, especially microbiome, host, and environmental interactions, into biological control development and applications. We explore ecological factors that may influence microbial biocontrol agents’ efficacy and discuss key research avenues forward.

This article is a review of modern conceptions concerning the interaction between a pathogen and a host plant at the molecular level. In particular, the basic principles of plant immunity and the mechanisms by which pathogens overcome this immunity are described. In this respect, special attention is paid to information about the interaction of the causative agent of late blight disease oomycete Phytophthora infestans (Mont.) de Bary with its host potato. This is due to the fact that late blight is the largest economically significant problem for modern potato farming. Despite the fact that the causative agent of late blight has been known to science for a long time, there are many unresolved issues related to the biology of this pathogen. Therefore, to create new potato varieties with high resistance to late blight, it is necessary to obtain new knowledge about the interaction of the polygenic plant resistance system with the determinants of pathogenicity of P. infestans.

Three Solanaceae hosts (TSHs), S. tuberosum, N. benthamiana and S. lycopersicum, represent the three major phylogenetic clades of Solanaceae plants infected by Phytophthora infestans, which causes late blight, one of the most devastating diseases seriously affecting crop production. However, details regarding how different Solanaceae hosts respond to P. infestans are lacking. Here, we conducted RNA-seq to analyze the transcriptomic data from the TSHs at 12 and 24 h post P. infestans inoculation to capture early expression effects. Macroscopic and microscopic observations showed faster infection processes in S. tuberosum than in N. benthamiana and S. lycopersicum under the same conditions. Analysis of the number of genes and their level of expression indicated that distinct response models were adopted by the TSHs in response to P. infestans. The host-specific infection process led to overlapping but distinct in GO terms and KEGG pathways enriched for differentially expressed genes; many were tightly linked to the immune response in the TSHs. S. tuberosum showed the fastest response and strongest accumulation of reactive oxygen species compared with N. benthamiana and S. lycopersicum, which also had similarities and differences in hormone regulation. Collectively, our study provides an important reference for a better understanding of late blight response mechanisms of different Solanaceae host interactions.