Fungal Pathogens and Spores Study Guide Exam 2

Local Infections and Spore Types

• Local infections occur on the surface of plants, leading to the perception of a systemic spread.
  • The perceived spread is due to additional spores being dispersed to various locations, where they induce spore generation.

Types of Spores in Diseases

• Discussion centers around spore types for specific diseases.
  • Wheat disease has five spore types.
  • Cedar apple rust has four spore types.

Pathogen Life Cycle and Hosts

• Both wheat disease and cedar apple rust require two hosts, classifying them as heteroecious pathogens.
  • The term "heteroecious" denotes needing two different hosts.

Spore Production and Life Cycle Types

• The life cycle of the pathogen can be divided based on the number of spores produced:
  • Macrocyclic: Produces five spores.
  • Microcyclic: Produces two spores.
  • Demicyclic: Produces four spores.

Pathogenic Classification

• Cedar apple rust is identified as Gymnosporangium juniperi.
  • Macrocyclic spores lead to significant spore production, which can be remembered using the term "macro" for big.
  • Microcyclic spores are associated with fewer spore types and smaller production.

Different Pathogen Groups

• Discusses various spores and their classifications:
  • Autoecious pathogens infect a single host.
  • Example provided of horn diseases, which are microcyclic and produce fewer spores.

Lower Fungi and Characteristics

• The study moves into lower fungi classification, encompassing:
  • Zygomycetes (true fungi).
  • Oomycetes (fungal-like organisms).
  • They can move using flagella at certain life stages.
  • Characteristics include lacking cross-walls and being broadly defined as semichitinous.

Reproductive Structures in Oomycetes

• Zoospores are the asexual motile spores, distinguished by:
  • Two flagella used for movement in water.
  • Produced inside a zoosporangium (a specialized structure).
• Sexual reproduction involves oogonia (female) and antheridia (male) forming an oospore after fertilization.
  • Unique characteristic of unequal sized gametes in this reproduction.

Rhizopus Species and Disease

• The Zygospore is a significant characteristic of zygomycetes, formed from two equal-sized gametes.
  • Soft rot is identified with Rhizopus species, a notable disease associated with zygomycetes.

Identification of Deuteromycetes Structures

• Discusses structures associated with Deuteromycetes:
  • Produce asexual conidia through various structures:
  • Conidiophore (spore-producing structure).
  • Pycnidia (thick-walled, pear-shaped structure).
  • Acervulus (saucer-shaped structure).
  • Sporangium and chlamydospore (resting spores).
  • Chlamydospores are formed by differentiation of a fungal cell and burst through plant surfaces.

Ascomycetes Characteristics

• Ascomycetes produce ascospores within an ascus, a structure that provides protection during spore development.
  • They generate fruiting bodies (mushrooms) visible when mature, housing ascospores in multiples of eight.
  • Differentiation between structures includes cleistothecium, perithecium, and apothecium.

Comparison and Distinctions of Fungal Pathogens

• Distinctions between structures like perithecium and pycnidium are essential for identification.
• Basidiomycetes offer basidiospores formed from teliospores, highlighting their lifecycle differences.
  • Disease mechanisms discussed include wheat stem rust with its specific lifecycle and spore types.

Recognition of Disease Symptoms

• Emphasis on recognizing and memorizing distinct disease symptoms and names shown on study guides or exams.
• Instructors will provide diseases in recognizable formats for easier identification.

Study Guide Suggestions

• Students are encouraged to review their notes, emphasizing:
  • Symptoms for each disease, distinguishing characteristics, and spore structure understanding.
• Exam format will include visual recognition or multiple-choice questions based on their guide.

Additional Topics

• Discussion on typical fungal diseases includes:
  • Early blight in tomatoes (concentric brown rings).
  • Asymmetric wilting and distinct symptoms associated with tomato diseases.
  • Review of other diseases and their characteristic shapes or structures as identified in their study materials.