Fungus Hemileia Vastatrix Research Articles

Respuesta de la roya (Hemileia vastatrix) frente a condiciones climáticas y aplicaciones de fungicidas en el cultivo de café (Coffea arabica) bajo sombra

Coffee leaf rust (Hemileia vastatrix) was first reported in 1869 on a plantation on the island of Sri Lanka, Asia, and has since spread to all coffee-growing regions far from its center of origin. The coexistence between the coffee plant, primarily Coffea arabica, and the fungus Hemileia vastatrix leads to coevolution, which manifests in significant genetic variability in the plant’s resistance to the disease and the fungus’s virulence towards the plant (Avelino and Rivas, 2013). The trophic relationships between the fungus and the host are influenced by soil moisture, fruit load, genetic resistance, precipitation, relative humidity, and temperature; these are the main factors affecting plant colonization (Filho and Astorga, 2015). In this study, the behavior of H. vastatrix was recorded through sampling to describe the relationship between disease incidence and environmental conditions, such as precipitation, temperature, and relative humidity, over an 18-month period at the Santa Lucía Experimental Farm (FESL) in Heredia, Costa Rica. The main findings demonstrated that the use of triazole fungicides and copper hydroxide can maintain disease incidence below 7%, despite contributions to its development from precipitation and increased temperatures, but not from increased relative humidity. Proper management of coffee leaf rust and the presence of shade can help reduce the incidence of the disease in the coffee plantation at FESL.

Use of artificial intelligence in the detection of coffee rust: An exploratory systematic review

Coffee rust, caused by the fungus Hemileia vastatrix, is a fungal disease that affects coffee production and quality, so its early detection is crucial to prevent massive outbreaks and protect production. This article analyzes the most effective factors, the algorithms used, the accuracy of the models, and the challenges in the detection of coffee rust, through an exploratory systematic review of 35 empirical articles obtained from Scopus, IEEE Xplore and SciELO. The review identifies that the most determinant factors for detection include humidity, temperature and the presence of shade. The most commonly used algorithms are Convolutional Neural Networks (CNN), Support Vector Machines (SVM) and Random Forest, highlighting CNN for its ability to process and analyze images with an accuracy of 99.57%, followed by Artificial Neural Networks (ANN) with 98% and SVM with 96%. However, it is concluded that challenges remain such as the need for high quality labeled datasets, variability in environmental conditions and implementation costs. This study provides a comprehensive overview of recent advances and areas for improvement in coffee rust detection, providing information for researchers, practitioners and decision makers in the agricultural sector.

Unravelling the role of key genes involved coffee leaf rust resistance

The biotrophic fungus Hemileia vastatrix is the pathogen responsible for coffee leaf rust, a devastating disease in several coffee-producing countries. Despite the importance of studying the interaction between Coffea and H. vastatrix, a more comprehensive understanding of the mechanisms involved in this pathosystem is necessary. The role of eight candidate genes was analyzed aiming at identifying and validating new important coffee resistance genes and understanding their interaction with H. vastatrix. These genes were identified in the most important sources of coffee resistance, the Híbrido de Timor CIFC 832/2 and CIFC 832/1. Previous works found six resistance genes and, in our research, other two new genes were identified in BAC clones and validated by RT-qPCR during compatible and incompatible interactions between Coffea and H. vastatrix. An interactome approach was performed using Coffea-H. vastatrix and Coffea-Coffea proteins to better understand the biological process and the interaction of the host-pathogen. Two networks of interactions from the compiled data were built focused on candidate genes associated with pre-haustorial resistance (12 and 24 h.a.i) in coffee plants against the pathogen. The results showed, for the first time, differentially expressed proteins (DEPs) positively regulated in the incompatible interaction Coffea-H. vastatrix. These coffee proteins interact with each other and with secreted and/or transmembrane pathogen proteins. The obtained results also show that DEPs found are involved in important plant defense pathways such as pathways associated with the response to wounds, signaling, regulation of the innate immune response and the transmembrane receptor protein serine/threonine kinase pathway. The present work shows the involvement of genes in both pathogen recognition and signaling cascades, which act in pre-haustorial defense mechanisms of HdT coffee. Therefore, the candidate genes analyzed, together with the biological processes elucidated, have the potential to contribute to the development of new control strategies against the fungus H. vastatrix within coffee breeding programs aiming to develop cultivars with durable resistance.

Leaf surface microbiota transplantation confers resistance to coffee leaf rust in susceptible Coffea arabica.

Coffee leaf rust, caused by the fungus Hemileia vastatrix, has become a major concern for coffee-producing countries. Additionally, there has been an increase in the resistance of certain races of the fungus to fungicides and breeding cultivars, making producers use alternative control methods. In this work, we transplanted the leaf surface microbiota of rust-resistant coffee species (Coffea racemosa and Coffea stenophylla) to Coffea arabica and tested whether the new microbiota would be able to minimize the damage caused by H. vastatrix. It was seen that the transplant was successful in controlling rust, especially from C. stenophylla, but the protection depended on the concentration of the microbiota. Certain fungi, such as Acrocalymma, Bipolaris, Didymella, Nigrospora, Setophaeosphaeria, Simplicillium, Stagonospora and Torula, and bacteria, such as Chryseobacterium, Sphingobium and especially Enterobacter, had their populations increased and this may be related to the antagonism seen against H. vastatrix. Interestingly, the relative population of bacteria from genera Pantoea, Methylobacterium and Sphingomonas decreased after transplantation, suggesting a positive interaction between them and H. vastatrix development. Our findings may help to better understand the role of the microbiota in coffee leaf rust, as well as help to optimize the development of biocontrol agents.

Antifungal Activity of Phyllospheric Bacteria Isolated from Coffea arabica against Hemileia vastatrix.

Peru is one of the leading countries that produce and export specialty coffees, favorably positioned in the international markets for its physical and organoleptic cup qualities. In recent years, yellow coffee rust caused by the phytopathogenic fungus Hemileia vastatrix stands out as one of the main phytosanitary diseases that affect coffee culture yields. Many studies have demonstrated bacteria antagonistic activity against a number of phytopathogen fungi. In this context, the aim of this work was to select and characterize phyllospheric bacteria isolated from Coffea arabica with antagonistic features against coffee rust to obtain biocontrollers. For that purpose, a total of 82 phyllospheric bacteria were isolated from two coffee leaf rust-susceptible varieties, typica and caturra roja, and one tolerant variety, catimor. Of all the isolates, 15% were endophytic and 85% were epiphytes. Among all the isolates, 14 were capable of inhibiting the mycelial radial growth of Mycena citricolor, and Colletotrichum sp. 16S rRNA gene sequence-based analysis showed that 9 isolates were related to Achromobacter insuavis, 2 were related to Luteibacter anthropi and 1 was related to Rodococcus ceridiohylli, Achromobacter marplatensis and Pseudomonas parafulva. A total of 7 representative bacteria of each group were selected based on their antagonistic activity and tested in germination inhibition assays of coffee rust uredinospores. The CRRFLT7 and TRFLT8 isolates showed a high inhibition percentage of urediniospores germination (81% and 82%, respectively), similar to that obtained with the chemical control (91%). An experimental field assay showed a good performance of both strains against rust damage too, making them a promising alternative for coffee leaf rust biocontrol.

Advancing Coffee Leaf Rust Disease Management: A Deep Learning Approach for Accurate Detection and Classification Using Convolutional Neural Networks

Coffee Leaf Rust (CLR), caused by the fungus Hemileia vastatrix, poses a severe threat to global coffee production. Timely detection is critical for effective control measures. This study employs Convolutional Neural Networks (CNNs) to enhance CLR detection accuracy. Traditionally, this task relies on expert assessment. DL emerges as a promising approach, capable of autonomously extracting salient features. Our model, trained on a diverse dataset, accurately identifies CLR. Using 1365 meticulously curated images, the model undergoes rigorous preprocessing and augmentation. The DL-based approach achieves remarkable accuracy (98.89%), precision (99.00%), recall (98.07%), and an F1 score of (98.55%). These outcomes establish the CNN model as a proficient system for precise, real-time CLR diagnosis. This study contributes to the creation of an efficient system, safeguarding coffee orchard vitality and productivity.

First Occurrence of Coffee Leaf Rust Caused by Hemileia vastatrix on Coffee in Saudi Arabia

Coffee leaf rust (CLR) is a major disease of Arabica coffee caused by the biotrophic fungus Hemileia vastatrix. Jazan region in Saudi Arabia has long been one of the last coffee-producing regions in the world free of this disease. In August 2023, CLR was initially observed in coffee plantations located in Fyfa district one of the main coffee-producing mountains of Jazan region. The source of the infection is unknown, however CLR could have entered Jazan from the nearest coffee-producing locations that haven the pathogen. During a scheduled survey in August 2023, symptoms were observed including yellowish-orange lesions that frequently combined to form chlorotic lesions and exhibited the powdery appearance of yellow uredospores on the abaxial surface of leaves. The uredospores and teliospores were microscopically examined and their morphology matched the previously published description for H. vastatrix. The identity of H. vastatrix specimens was further confirmed based on PCR amplification and sequencing of ITS, sharing a 99–100% identity with previously published sequences, as belonging to H. vastatrix. The pathogenicity of H. vastatrix specimens was investigated on Coffee arabica plants under growth chamber conditions, and all were pathogenic relative to control, with 100% of disease incidence, therefore fulfilling Koch’s postulates. Based on our findings, this is the first documentation of H. vastatrix causing CLR in Saudi Arabia.

The coffee leaf rust pandemic: An ever‐present danger to coffee production

AbstractCoffee leaf rust (CLR) is caused by the biotrophic pathogenic fungus Hemileia vastatrix. Despite being the most researched coffee disease, mysteries still exist relating to its epidemiology and biology. The objective of this work is to highlight past and present events concerning this prominent coffee disease. We start with an historical overview of the homeland of Coffea arabica, the Afromontane forest of south‐west Ethiopia, and then follow its journey across the globe linked to colonial trade and power struggles. We report the relevance of CLR to coffee production today, with a focus on the Americas and summarize unproven hypotheses in relation to the cause of recent epidemics. We present an original hypothesis concerning the first major outbreak occurring in 1869 in Ceylon (Sri Lanka), based on geopolitical connections to global trade. We review old and new options for management of the disease. The likelihood of a yet undetected alternate host of H. vastatrix is also considered as an additional piece of the epidemiological puzzle. Finally, we reflect on the interactions between H. vastatrix and a changing climate. By better understanding past events, linked to CLR, we may be better prepared for future outbreaks.

Essential Oils and Antagonistic Microorganisms as Eco-Friendly Alternatives for Coffee Leaf Rust Control.

Coffee leaf rust (CLR) is caused by the biotrophic fungus Hemileia vastatrix Berk. & Br., a disease of economic importance, reducing coffee yield up to 60%. Currently, CLR epidemics have negatively impacted food security. Therefore, the objective of the present research study is to show a current framework of this disease and its effects on diverse areas, as well as the biological systems used for its control, mode of action, and effectiveness. The use of essential plant oils and antagonistic microorganisms to H. vastatrix are highlighted. Terpenes, terpenoids, and aromatic compounds are the main constituents of these oils, which alter the cell wall and membrane composition and modify the basic cell functions. Beneficial microorganisms inhibit urediniospore germination and reduce disease incidence and severity. The antagonistic microorganisms and essential oils of some aromatic plants have great potential in agriculture. These biological systems may have more than one mechanism of action, which reduces the possibility of the emergence of resistant strains of H. vastatrix.

Genome sequence of Hemileia vastatrix Berk. and Br. (Race I), the causal agent of coffee leaf rust, isolate from Risaralda, Colombia.

Coffee leaf rust, caused by the fungus Hemileia vastatrix (Basidiomycota; Pucciniomycota), is a devastating disease spread worldwide. To improve the available genomes, we use PacBio HiFi sequencing enhanced by Dovetail Omni-C chromatin conformation capture to assemble a highly contiguous 747.98 Mb genome of an isolate collected from Coffea arabica.

Intensity of Leaf Rust Disease on Four Robusta Coffee Clones in Natar, South Lampung

Lampung Province is the producer and exporter of coffee in Indonesia. Leaf rust disease is an important disease in coffee and is caused by fungus Hemileia vastatrix Berk & Br. This disease has spread to all coffee cultivation areas worldwide, including Indonesia. The incidence of this disease can cause production losses and reducing productivity up to 50%. The aim of the study was to determine the intensity of leaf rust disease in four Robusta coffee (Coffea canephora) clones in Natar, South Lampung Regency, Lampung Province, namely BP 436, BP 534, BP 939 and SA 203. The experiment was conducted in a completely randomized block design, with four clones, 30 replicates, and 30 evaluation samples. The intensity of disease attacks was calculated using Townsend-Heuberger formula. The results indicated that the intensity of disease attack on four clones was classified as a mild attack, with the lowest attack level was on BP 534 clone (5.63%). Robusta coffee is relatively tolerant to leaf rust disease, however management of this disease must be applied to prevent greater yield losses.

Genetic diversity and structure of the coffee leaf rust fungus Hemileia vastatrix across different coffee management systems in Ethiopia.

Although coffee leaf rust (CLR), caused by Hemileia vastatrix, poses an increasing threat to coffee production in Ethiopia, little is known regarding its genetic diversity and structure and how these are affected by coffee management. Here, we used genetic fingerprinting based on sequence-related amplified polymorphism (SRAP) markers to genotype H. vastatrix samples from different coffee shrubs, across 40 sites, covering four coffee production systems (forest coffee, semi plantation coffee, home garden coffee, and plantation coffee) and different altitudes in Ethiopia. In total, 96 H. vastatrix samples were successfully genotyped with three primer combinations, producing a total of 79 scorable bands. We found 35.44% of amplified bands to be polymorphic, and the polymorphic information content (PIC) was 0.45, suggesting high genetic diversity among our CLR isolates. We also found significant isolation-by-distance across the samples investigated and detected significant differences in fungal genetic composition among plantation coffee and home garden coffee and a marginally significant difference among plantation coffee and forest coffee. Furthermore, we found a significant effect of altitude on CLR genetic composition in the forest coffee and plantation systems. Our results suggest that both spore dispersal and different selection pressures in the different coffee management systems are likely responsible for the observed high genetic diversity and genetic structure of CLR isolates in Ethiopia. When selecting Ethiopian coffee genotypes for crop improvement, it is important that these genotypes carry some resistance against CLR. Because our study shows large variation in genetic composition across relatively short geographical distances, a broad selection of rust isolates must be used for coffee resistance screening.

Isolation and identification of antagonistic fungi on coffee leaf rust in the Dieng highlands of Banjarnegara, Indonesia

BackgroundCoffee is an important plantation crop in Indonesia. The coffee cultivation process was disrupted due to the fungus Hemileia vastatrix which causes rust disease. Biological control has the potential to suppress disease development. The diversity of antagonistic fungi such as Trichoderma in nature is very abundant, so it is necessary to explore and find Trichoderma which has the potential as a biological agent in controlling coffee leaf rust. The research aimed to obtain antagonist fungi that have the potential as biological agents in controlling coffee leaf rust naturally in the coffee plant ecosystem.ResultMorphology of a local antagonist fungus isolate, coded TBK1, was identified as Trichoderma atroviride which had the potential to naturally control coffee leaf rust by H. vastatrix through a mycoparasitic mechanism.ConclusionIn the Dieng Plateau, Banjarnegara Indonesia, an antagonistic fungus as a biological agent, T. atroviride, was found to control H. vastatrix coffee leaf rust.

Growth of Four Varieties of <i>Coffea arabica</i> L. Biofertilized with <i>Rhizophagus intraradices</i> and <i>Azospirillum brasilense</i> in Nursery

Coffee production has decreased due to environmental and management factors. The current plantations are old and unproductive, also due to the rust problem, caused by the fungus Hemileia vastatrix Berk & Br. Furthermore, the shade in the production systems has decreased with the consequent increase in soil erosion, in addition to the increase in agrochemicals. Currently, the planting of new varieties with resistance to the fungus is increasing. Furthermore, it has been shown that various biofertilized perennial crops in nursery favor their growth. In this study, the effect of applying two beneficial microorganisms, Rhizophagus intraradices and/or Azospirillum brasilense, to the planting of four varieties of Coffea arabica L. was evaluated. The coffee varieties marseillase, geisha, sarchimor and costa rica 95 were established in bags with the following treatments: 1) control, 2) R. intraradices, 3) A. brasilense, 4) R. intraradices + A. brasilense. Morphological and physiological yield components were recorded 168 days after transplanting. Data was analyzed statistically and differences between treatments were compared according to Tukey (p ≤ 0.05). The results indicate that individual or combined biofertilization of microorganisms favors dry matter allocation compared to the control and the same is differentially assigned to the stem and root. The Specific Leaf Area (SLA) also showed differential response between applications of the microorganisms, in two varieties it increased when they were applied alone and in the others when they were applied together.

Antifungal activity of poly(ε-caprolactone) nanoparticles incorporated with Eucalyptus essential oils against Hemileia vastatrix.

Coffee (Coffea L.) is one of the main crops produced globally. Its contamination by the fungus Hemileia vastatrix Berkeley and Broome has been economically detrimental for producers. The objective of this work was to extract and characterize the essential oils from Eucalyptus citriodora Hook, Eucalyptus camaldulensis Dehn and Eucalyptus grandis Hill ex Maiden, produce and characterize nanoparticles containing these essential oils and evaluate the invivo and invitro antifungal activity of free and nanoencapsulated essential oils. The principal constituent of the essential oil from E. citriodora was citronellal; that from E. grandis was α-pinene; and that from E. camaldulensis was 1,8-cineol. The invitro antifungal activity against the fungus H. vastatrix was 100% at a concentration of 1000 μl l-1 for all the oils and nanoparticles containing these natural products. The sizes of the nanoparticles produced with the essential oils from E. citriodora, E. camaldulensis and E. grandis were 402·13 nm, 275·33 nm and 328·5 nm, respectively, with surface charges of -11·8 mV, -9·24 mV and - 6·76 mV, respectively. Fourier transform infrared analyses proved that the encapsulation of essential oils occurred in the polymeric matrix of poly(ε-caprolactone). The incorporation of essential oils into biodegradable poly(ε-caprolactone) nanoparticles increased their efficiency as biofungicides in the fight against coffee rust, decreasing the severity of the disease by up to 90·75% after treatment with the nanoparticles containing the essential oil from E. grandis.

HOLISTIC RISK INDEX FOR DECISION-MAKING IN MANAGEMENT OF RUST Hemileia vastatrix IN COFFEE PLANTATIONS IN HONDURAS

One of the diseases that most affect coffee plantations (Coffea arabica) is the fungus Hemileia vastatrix, which causes rust. The lack of a decision-making method with a holistic approach limits the effective management of this disease. Therefore, this study aimed to determine the Holistic Risk Index (HRI) for rust in coffee-growing zones of El Lago de Yojoa, El Paraíso and Olancho, Honduras. First, a participatory diagnosis of coffee industry was implemented; surveys were conducted to determine the socioeconomic status of 43 coffee producers, also their coffee farms were sampled. The diagnosis indicated that deficient management of the coffee plantations, the incidence of pests and a precarious economy for coffee growers were the most important problems. One threat variable (leaves with rust); three vulnerability variables (altitude, coffee variety and shade); and three response capacity variables (technification, harvesting and productive coffee trees) were identified. The HRI and resilience were related by means of a power equation and from that result the criteria for categories were determined. When comparing the three coffee-growing zones with a multivariate analysis of variance and a canonical discriminant analysis for the set of HRI component values, the El Paraíso coffee-growing zone was different from the Lago de Yojoa zone, but these two zones did not differ from the Olancho zone. The same result was found for the response capacity, where the harvest and technification variables had a greater influence in El Paraíso and the productive category variable of coffee trees was more important in Olancho. Finally, a work plan was proposed to reduce the risk and increase the resilience of producers to rust.

Coffee Leaf Rust (Hemileia vastatrix) from the Recent Invasion into Hawaii Shares a Genotypic Relationship with Latin American Populations.

Hawaii has long been one of the last coffee-producing regions of the world free of coffee leaf rust (CLR) disease, which is caused by the biotrophic fungus Hemileia vastatrix. However, CLR was detected in coffee farms and feral coffee on the island of Maui in February 2020 and subsequently on other islands of the Hawaiian archipelago. The source of the outbreak in Hawaii is not known, and CLR could have entered Hawaii from more than 50 coffee-producing nations that harbor the pathogen. To determine the source(s) of the Hawaii inoculum, we analyzed a set of eleven simple sequence repeat markers (SSRs) generated from Hawaii isolates within a dataset of 434 CLR isolates collected from 17 countries spanning both old and new world populations, and then conducted a minimum spanning network (MSN) analysis to trace the most likely pathway that H. vastatrix could have taken to Hawaii. Forty-two multilocus genotypes (MLGs) of H. vastatrix were found in the global dataset, with all isolates from Hawaii assignable to MLG 10 or derived from it. MLG 10 is widespread in Central America and Jamaica, making this region the most probable source of inoculum for the outbreak in Hawaii. An examination of global weather patterns during the months preceding the introduction of CLR makes it unlikely that the pathogen was windborne to the islands. Likely scenarios for the introduction of CLR to Hawaii are the accidental introduction of spores or infected plant material by travelers or seasonal workers, or improperly fumigated coffee shipments originating from Central America or the Caribbean islands.

Double-Staining Method to Detect Pectin in Plant-Fungus Interaction.

Plant cells use different structural mechanisms, either constitutive or inducible, to defend themselves from fungal infection. Encapsulation is an efficient inducible mechanism to isolate the fungal haustoria from the plant cell protoplast. Conversely, pectin, one of the polymeric components of the cell wall, is a target of several pectolytic enzymes in necrotrophic interactions. Here, a protocol to detect pectin and fungal hyphae through optical microscopy is presented. The pectin-rich encapsulation in the cells of coffee leaves infected by the rust fungus Hemileia vastatrix and the mesophyll cell wall modification induced by Cercospora coffeicola are investigated. Lesioned leaf samples were fixed with the Karnovsky solution, dehydrated, and embedded in glycol methacrylate for 2-4 days. All steps were followed by vacuum-pumping to remove air in the intercellular spaces and improve the embedding process. The embedded blocks were sectioned into 5-7 µm thick sections, which were deposited on a glass slide covered with water and subsequently heated at 40 °C for 30 min. Next, the slides were double-stained with 5% cotton blue in lactophenol to detect the fungus and 0.05% ruthenium red in water to detect pectin (acidic groups of polyuronic acids of pectin). Fungal haustoria of Hemileia vastatrix were found to be encapsulated by pectin. In coffee cercosporiosis, mesophyll cells exhibited dissolution of cell walls, and intercellular hyphae and conidiophores were observed. The method presented here is effective to detect a pectin-associated response in the plant-fungi interaction.

Detecting Hemileia vastatrix using Vision AI as Supporting to Food Security for Smallholder Coffee Commodities

The loss of food crops during the COVID-19 pandemic threatens food security in Indonesia as one of the world’s top coffee producers. This affects the insecurity of coffee commodities which is influenced by several factors other than the pandemic such as pests, plant diseases, and extreme weather. Plant diseases, such as leaf rust, are a significant factor in the insecurity problem in coffee commodities. The fungus Hemileia vastatrix B et Br causes leaf rust disease, which is a pest that frequently damages coffee plants. This disease not only interferes with plant growth but also causes a decrease in coffee quality and quantity. This initial research aims to carry out early prevention of these diseases as supporting to food security in smallholder coffee commodities. An AI-based visual detection application is the result of this research. We collected 100 images of coffee leaves from various coffee plants. The image is reshaped to 256 x 256 pixels and randomly trimmed to 224 x 224 pixels to fulfill the size requirements of a standard Deep Learning technique. Each image was classified into two classes by a plant pest and disease specialist. The dataset was divided into training, validation, and testing series with a ratio of 60:20:20 for training procedures. The Convolutional Neural Network (CNN) research method used a variation of the ResNet CNN model with 18 layers. The best model validation was 59%.

An Overview of the Mechanisms Involved in Coffee-Hemileia vastatrix Interactions: Plant and Pathogen Perspectives

Coffee is one of the most consumed beverages in the world. It is also one of the most globally traded commodities. Coffee leaf rust (CLR), caused by the biotrophic fungus Hemileia vastatrix, is the most important disease affecting Arabica coffee growing worldwide, leading to significant yield losses if no control measures are applied. A deep understanding of the complex mechanisms involved in coffee-H. vastatrix interactions, such as the pathogen variability and the mechanisms governing plant resistance and susceptibility, is required to breed efficiently for durable resistance and design new approaches for crop protection. Here we summarize our current understanding across multiple areas related to pathogen infection, variability and candidate effectors, breeding for disease resistance, and the various components of the coffee immune system, by reviewing a comprehensive body of research on CLR and the advances recently made. We also update information about the defense responses activated by the application of plant resistance inducers, a promising alternative to fungicides in the control of CLR. Moreover, we identify and discuss future directions for further research.