Ecology of Pathogenic Fungi | Fungal entomopathogens’ interactions with the environment

Ecology of Pathogenic Fungi

1. ECOLOGY OF ENTOMOPATHOGENIC FUNGI

2. TABLE OF CONTENTS Introduction ( EPF) Fungal entomopathogens’ interactions with the environment Effects of environmental conditions on EPF

3. Entomopathogenic Fungi Entomopathogenic fungi are microorganisms that infect and kill insects and arthropods. Most of EPFs have been receiving increasing attention as biocontrol agents to control insect pests.

4. MODE OF INFECTION OF FUNGI

5. Ecology of Entomopathogenic Fungi EPF as biopesticides can develop more efficient and more diversified applications Knowledge of fundamental aspects of ecology is considered necessary

6. FUNGAL ENTOMOPATHOGENS INTERACTIONS WITH THE ENVIRONMENT Entomopathogenic fungi as soil-dwelling microorganisms that infect and kill insects through cuticle penetration. Used as a biocontrol agent. These interactions display how fungi can play a positive role, by directly affecting insect pest development or inducing plant resistance and defense reactions. Soil-borne fungus,  B. bassiana  is recorded to infect more than 700 insect species

7. EPF RELATIONSHIP WITH ENVIRONMENT Fungi are exploited as a feeding resource by mycophagous insects, while in turn many fungi are entomopathogenic and make use of insects as a nutrient substrate. Interactions between these organisms which, far from being merely antagonistic, may also involve mutualistic relationships.

8. EFFECTS OF ENVIRONMENTAL CONDITIONS ON EPF Environmental conditions, particularly humidity and temperature, and to lesser extent light and air are very imp in the infection and sporulation of EPF. Temperature Optimum temp =20 to 30 c Spores may tolerate High temp: 80 to 100C for approx 1 hour Low temp: 7 to 10C Deuteromycotina found in tropical and subtropical areas, tends to germinate at optimal temp. whereas entomopthorales need lower optimum temp.

9. Humidity High humidity is required for sporulation and release of conidia. EFFECTS OF ENVIRONMENTAL CONDITIONS ON EPF A film of water may be necessary for conidial germination. The microclimatic moisture greatly affects conidial production. Conidiophores are stimulated by low humidity and darkness.

10. LIGHT Short UV rays may kill spores or disperse in the air. Spore germination is less affected by light. Many EPF sporulate early in the morning

11. NUTRITIONAL ENVIRONMENT The absence , quality, quantity of nutrient, cuticlar lipids present in insect integuments may affect the spore germination So the survival of fungal propagules varies with environmental conditions and type of substrate.

12. Soil ecology of EPF: The soil environment is an important reservoir for a wide variety of EPF which can make an important contribution to the control of insect populations Many species of (Ascomycota) fungi live in the soil for most of their life cycle. Beauveria spp., Metarhizium spp and Cordyceps spp. are common genera found in agricultural and forest soils and have the greatest potential for biological control Soil properties: Soils good in acidity, the heaviness of soil texture and high organic matter content

13. Leaf litter ( dead plant material) and the soil layer under it are the main reservoirs where EPF have a chance to come into contact, with hosts that constantly live in the forest floor environmeNT Entomopathogenic fungi provide an invaluable service of suppressing pest populations and preventing pest outbreaks in forest habitats Interaction of EPF and plant’s root system: This interaction increase plant defenses, particularly against plant pathogens. For example, B. bassiana and Metarhizium spp. trigger immunity and induce several JA and SA signaling pathway genes .

14. EPFs induce systemic resistance in plants against other biotic stresses such as pathogens and phytoparastic nematodes promote plant growth increase yields improve plant nutrition boost root development and alleviate abiotic stresses such as salinity or iron (Fe) chlorosis EPF increases the bioavailability of certain nutrients such as , Cu, fe and Zn .

15. . Fe chlorosis is the yellowing of young leaves due to the inhibition of chlorophyll synthesis, which may ultimately reduce plant growth and yield In response to low Fe availability, most fungi develop specific mechanisms to obtain Fe applying Beauveria bassiana strain to tomato seeds and wheat grown on artificial substrates was found to improve Fe nutrition under certain conditions , and applying Metarhizium brunneum strain to the soils used to grow sorghum, wheat and sunflower improved the Fe bioavailability and/or plant growth....