Spread Of Fungal Pathogens Research Articles

Exploring the biocontrol and plant growth-promoting potential of Streptomyces kronopolitis isolate SA18 against durian foliar blight and dieback disease

Abstract. Kraivuttinun P, Pirapak K, Pinnak P, Pirapak W. 2024. Exploring the biocontrol and plant growth-promoting potential of Streptomyces kronopolitis isolate SA18 against durian foliar blight and dieback disease. Biodiversitas 25: 2661-2669. Actinomycetes have been extensively studied for their potential as plant growth promoters and biocontrol agents against fungal plant pathogens. In Thailand, durian is a highly valuable fruit crop, celebrated for its delectable fleshy arils. Rhizoctonia solani destruction causes foliar blight and dieback, a severe disease on durian plantations. Our investigation objective was to isolate, select, and identify actinomycetes that exhibit antagonistic properties and could improve the growth of durian. This study revealed that 37 actinomycete isolates were obtained, comprising 14 endophytic isolates and 23 soil-derived actinomycete isolates from durian plantations in Thailand's Uttaradit and Sukhothai Provinces. All actinomycete isolates demonstrated the ability to inhibit pathogen growth through in vitro antagonistic bioassay. Isolate SA18 exhibited the highest percentage inhibition of radial growth against R. solani isolate 01, achieving an impressive 92% inhibition. Furthermore, isolate SA18 demonstrated the capacity to produce 5.91 ?g/mL of indole acetic acid after seven days of culture, increasing to 45.72 ?g/mL after 14 days. This isolate also exhibited phosphate solubilization ability. In the detached leaf bioassay, isolate SA18 effectively controlled the spread of fungal pathogens, reducing disease severity significantly from 93.75% in the control treatment to 53.75% with a concentration of 108 spores/mL of isolate SA18. Morphological examination and 16S rRNA gene sequencing revealed that isolate SA18 formed smooth-surfaced spores in chains and showed a close relationship with Streptomyces kronopolitis based on the 16S rDNA sequence. This study is the first to report the presence of S. kronopolitis in soil samples collected from durian orchards in Thailand. This isolate can improve plant growth and control R. solani in bioassays. S. kronopolitis isolate SA18 can potentially be a biocontrol agent for durian plantations.

Inheritance of juvenile resistance to powdery mildew in barley accessions from Ethiopia

Background. Barley (Hordeum vulgare L.) is one of the key food crops, ranking fourth in the world in terms of sown area and production among cereals. Often, one of the main factors that reduces yield and product quality is the spread of fungal pathogens in commercial crops. Powdery mildew (causative agent: Blumeria graminis (DC.) Golovin ex Speer f. sp. hordei Marchal) is considered one of the most common and harmful among barley diseases. Plant resistance to B. graminis limits the spread of the disease, and the development of resistant cultivars prevents a decrease in plant productivity. The specificity of the host–pathogen relationship and the loss of efficiency in many genes determine the need for a continuous study of previously unexplored local barley forms and a search for new, most effective resistance genes.Materials and methods. The genetic control of juvenile resistance to B. graminis was studied in 14 accessions of spring barley from the Ethiopian (Abyssinian) center of crop origin. The natural population of the pathogen served as infectious material for infecting barley. The intensity and nature of sporulation as well as the qualitative reactions of plant tissues in response to the penetration of the fungus (necrosis and chlorosis) were accepted as indicators of resistance in the accessions. Powdery mildew resistance was assessed under laboratory and field conditions. The genetic control of the resistance trait was studied using the method of hybridological analysis followed by statistical processing.Results and conclusions. Barleys from the Ethiopian center of morphogenesis are characterized by great genetic diversity. Studying the inheritance of juvenile resistance to powdery mildew made it possible to ascertain the monogenic control of the trait in all studied forms. Ten barley accessions with one effective recessive resistance allele and four with the dominant control of the trait may be recommended for immunity-targeted breeding.

Characterization of chitinolytic bacteria isolated from Ipomea pes caprae

Chitin has substantial benefits in several sectors including agriculture. In the plant protection field, chitin can promote the growth of certain bacteria which has possibly controlled the spread of fungal pathogens. Thus, chitinolytic bacteria producing chitinase enzymes can inhibit the growth of fungi. The purpose of this study was to examine the morphological and physiological characteristics of chitinolytic bacteria which collected from Ipomea pes caprae in Makassar and its ability to produce chitinolytic enzymes on medial culture. The method started to grow the isolates on the nutrient agar which were added to colloidal chitin. Furthermore, the bacteria were identified by its color, form, elevation and edge as well as tested its physiological characteristics with KOH 3% test and catalase test. In addition, bacterial chitinolytic index was carried out by using the disc diffusion method. The results showed that each isolate had yellowish white and grayish white colors; morphological characters: round and irregular colony shapes, colony edges smooth and choppy as well as umbonature and convex elevations. The physiological test results indicate that all isolates had a positive response in the catalase test, one of the isolates reacted positively to the gram test and the others reacted negatively to the test. Each isolate had chitinolytic activity with indices of 0.10, 0.09, 0.70, and 0.11.

Transforming Polyethylene into Water-Soluble Antifungal Polymers

Petroleum-based polyolefin plastics currently possess highly unsustainable cradle-to-grave linear life cycles. Using them as a resource for the production of new functional polymers not only decreases the generated waste but also reduces our reliance on petroleum-derived monomers for traditional bottom-up synthesis of new polymeric materials. Herein, we demonstrate that polyethylene (PE), the most abundant plastic in production today, can be transformed into low-molecular-weight water-soluble antimicrobial polymers. In this proof-of-concept study, organocatalytic C–H aerobic oxidation of PE was first achieved to append reactive oxygenated and chloro functional groups onto the inert polymer chains, followed by further chemical modifications to form water-soluble amphiphilic polymers. Our first-generation polymer showed antimicrobial efficacy against opportunistic pathogenic Candida fungi without appreciable hemolysis even at high concentrations (2 mg/mL). The PE-derived antimicrobial polymer may find applications to combat the spread of fungal pathogens.

Obituary of Professor Ing. Karel Veverka, DrSc. (1943-2021)

Prof. Ing. Karel Veverka, DrSc. was an important figure in Czech agricultural phytopathology at the turn of the 20th and 21st centuries. His long, diverse experiences in the field of plant protection, combined with his excellent public speaking skills, led him to be recognized as one of the erudite experts of his time. His skillful presentations were widely appreciated at scientific conferences and seminars and at university lectures for students. All his scientific life, he kept contacts in the broader world of agricultural production, to which he was very close due to his personal experience. His expertise in chemical plant-protection products was unsurpassed. Beyond his own research and teaching activities, he always found time for the popularization of science. He published his achievements in both scientific journals and the popular-scientific press, being the author of numerous publications on plant protection, pesticides, the spread of fungal pathogens, diagnostics, and monitoring and epidemiology of phytopathogenic fungi.

The Diurnal Rhythm of Brassica napus L. Influences Contents of Sulfur-Containing Defense Compounds and Occurrence of Vascular Occlusions during an Infection with Verticillium longisporum

Reduction in atmospheric sulfur and intensified agriculture have led to sulfur deficiency, often correlated with a higher susceptibility to pathogens. The spread of fungal pathogens, such as the soil-born Verticillium longisporum, was observed. Defense responses of infected plants are linked to sulfur-containing compounds including glucosinolates (GSLs). Some pathogens infect their hosts at specific time periods during the day. To investigate the relation of sulfur-containing metabolites with diurnal effects of infection time points, Brassica napus plants cultivated at two different sulfur supplies, were infected with V. longisporum at four different time points during the day. It was demonstrated that 3, 7 and 14 days after inoculation the infected plants differed in their infection rate depending on the time point of infection. Additionally, infected plants had higher contents of sulfur-containing metabolites, such as specific GSLs, in comparison to non-infected plants. Sufficient sulfur fertilization was always reflected in higher contents of sulfur-containing compounds as well as a lower rate of infection compared to sulfur-deprived plants. On the microscopic level vascular occlusions in the hypocotyl were visible and the amount was dependent on the time point of infection. The results might be used to optimize sulfur fertilization to reduce susceptibility to V. longisporum.

Screening for Exotic Forest Pathogens to Increase Survey Capacity Using Metagenomics.

Anthropogenic activities have a major impact on the global environment. Canada's natural resources are threatened by the spread of fungal pathogens, which is facilitated by agricultural practices and international trade. Fungi are introduced to new environments and sometimes become established, in which case they can cause disease outbreaks resulting in extensive forest decline. Here, we describe how a nationwide sample collection strategy coupled to next-generation sequencing (NGS) (i.e., metagenomics) can achieve fast and comprehensive screening for exotic invasive species. This methodology can help provide guidance to phytopathology stakeholders such as regulatory agencies. Several regulated invasive species were monitored by processing field samples collected over 3 years (2013 to 2015) near high-risk areas across Canada. Fifteen sequencing runs were required on the Ion Torrent platform to process 398 samples that yielded 45 million reads. High-throughput screening of fungal and oomycete operational taxonomic units using customized fungi-specific ribosomal internal transcribed spacer 1 barcoded primers was performed. Likewise, Phytophthora-specific barcoded primers were used to amplify the adenosine triphosphate synthase subunit 9-nicotinamide adenine dinucleotide dehydrogenase subunit 9 spacer. Several Phytophthora spp. were detected by NGS and confirmed by species-specific quantitative polymerase chain reaction (qPCR) assays. The target species Heterobasidion annosum sensu stricto could be detected only through metagenomics. We demonstrated that screening target species using a variety of sampling techniques and NGS-the results of which were validated by qPCR-has the potential to increase survey capacity and detection sensitivity, reduce hands-on time and costs, and assist regulatory agencies to identify ports of entry. Considering that early detection and prevention are the keys in mitigating invasive species damage, our method represents a substantial asset in plant pathology management.

Source and spread of fungal pathogens causing crown rot disease in organic bananas

Source and spread of fungal pathogens causing crown rot disease in organic bananas

How changes in the dynamic of crop susceptibility and cultural practices can be used to better control the spread of a fungal pathogen at the plot scale?

A PDEs–ODEs model was developed to describe the spread of an airborne fungal pathogen on grapevine. The model was able to retrieve the main characteristics of the system: (1) a host growing during the whole season with time evolution in susceptibility, (2) a crop highly structured in rows with potential heterogeneities of plant growth and susceptibility within and between plots. These characteristics are modified by cultural management. Simulations were performed to test the effect of crop spatial heterogeneities, within and between plots, on the disease spread. Heterogeneities considered were the plant growth (vigour, earliness), susceptibility (susceptible vs resistant, treated vs untreated) and the spatial arrangements (patches vs rows). The main effect on disease reduction was obtained by arrangement in rows of susceptible and fully resistant plants.

Overexpression of cotton (<italic>Gossypium hirsutum</italic>) <italic>dirigent1</italic> gene enhances lignification that blocks the spread of <italic>Verticillium dahliae</italic>

Dirigent super-family abounds throughout the plant kingdom, especially vascular plants. To elucidate the function of cotton (Gossypium hirsutum) DIR genes in lignification, two cDNAs (designated GhDIR1 and GhDIR2) encoding putative dirigent proteins were isolated from cotton cDNA libraries. Real-time quantitative reverse transcription-polymerase chain reaction analysis revealed that GhDIR1 transcript was preferentially accumulated in cotton hypocotyls, whereas GhDIR2 was predominantly expressed in cotton fibers. Overexpression of GhDIR1 gene resulted in an increase in lignin content in transgenic cotton plants, compared with that of wild type. Histochemical assay revealed that the transgenic plants displayed more widespread lignification than that of wild type in epidermis and vascular bundle. Furthermore, the transgenic cotton plants displayed more tolerance to the infection of Verticillium dahliae. Our data suggest that GhDIR1 may be involved in cotton lignification which can block the spread of fungal pathogen V. dahliae.

Seasonal and Diurnal Patterns of Spore Release Can Significantly Affect the Proportion of Spores Expected to Undergo Long-Distance Dispersal

Many of the fungal pathogens that threaten agricultural and natural systems undergo wind-assisted dispersal. During turbulent wind conditions, long-distance dispersal can occur, and airborne spores are carried over distances greater than the mean. The occurrence of long-distance dispersal is an important ecological process, as it can drastically increase the extent to which pathogen epidemics spread across a landscape, result in rapid transmission of disease to previously uninfected areas, and influence the spatial structure of pathogen populations in fragmented landscapes. Since the timing of spore release determines the wind conditions that prevail over a dispersal event, this timing is likely to affect the probability of long-distance dispersal occurring. Using a Lagrangian stochastic model, we test the effect of seasonal and diurnal variation in the release of spores on wind-assisted dispersal. Spores released during the hottest part of the day are shown to be more likely to undergo long-distance dispersal than those released at other times. Furthermore, interactions are shown to occur between seasonal and diurnal patterns of release. These results have important consequences for further modelling of wind-assisted dispersal and the use of models to predict the spread of fungal pathogens and resulting population and epidemic dynamics.

Consumo de massas, biodiversidade e fitomelhoramento da banana de exportação 1920 a 1980

A exportação de banana, na América, foi constituída sob uma base genética extremamente limitada: ao longo de setenta anos, uma só variedade de banana, a Gros Michel, foi praticamente a única a ser vendida nos mercados norte-americanos. Esta variedade produzia grandes cachos, resistentes ao transporte, e dotados de um sabor e de uma casca que os consumidores norte-americanos identificavam como pertencentes a uma banana de qualidade. Entretanto, a Gros Michel também se mostrou muito suscetível a um grande número de patógenos fúngicos, incluindo o Mal do Panamá e a Sigatoka. A dinâmica histórica ocasionada, durante a primeira metade do século XX, pela propagação desse fungo, acelerou o aumentou dos índices de desmatamento, desestabilizou os sistemas de vida rural, aumentou os riscos à saúde dos trabalhadores do campo, e limitou os rendimentos das principais companhias de comércio de banana. Tais epidemias impeliram o governo britânico e a United Fruit Company a estabelecerem programas de fitomelhoramento, durante a década de 1920, tendo como meta o desenvolvimento de uma banana para exportação, que fosse resistente ao Mal do Panamá. Contudo, a criação de um híbrido que fosse capaz tanto de prosperar nas zonas tropicais, quanto de encontrar aceitação no mercado norte-americano, se mostrou uma tarefa de difícil realização. A história dos programas de melhoramento revela uma das principais contradições da agricultura do século XX: os mesmos processos de produção massificada, que tendem a reduzir a diversidade biológica a nível local e regional, permaneciam dependentes do acesso a de um banco genético "global", para manter níveis lucrativos de produção.

THE ROLE OF POTENTIAL BIOCONTROL AGENTS IN THE MANAGEMENT OF PEANUT ROOT ROT IN ARGENTINA

SUMMARY Cultural practices such as tillage and crop rotation can be used as components of pest-management programs. The appropriate combination of tillage systems and crops may favor the development of beneficial microorganisms, preventing the spread of fungal pathogens. A long-term field study was carried out to analyze the effect of crop management on the abundance of actinomycetes, Trichoderma spp., and Gliocladium spp., as potential biocontrol agents (PBAs), and their relationship with the incidence of peanut root rot caused by Fusarium solani. Soil samples were taken at sowing and harvest, and root rot incidence was evaluated at harvest. There was an inverse relationship between root rot incidence peanut PBA populations under no-till suggesting a possible role of PBAs in the control of F. solani, the incidence of root rot being low under no-till and disc harrow, associated with a high concentration of potential antagonists. However, this correlation was not observed when soybean preceded peanut, when the incidence of root rot was low despite relatively lower populations of biocontrol agents present in the soil, in comparison with maize as previous crop.