13356 - General Vegetal Pathology

Learning outcomes

Students will acquire knowledge on the general aspects of plant pathology, such as biology, symptomatology and diagnostics of the major infective diseases of crops (caused by virus, viroids, mollicutes, bacteria and fungi) and of the abiotic stress alterations.

Course contents

A) Prerequisites

Students attending this course will have good knowledge of agricultural chemistry, biology physiology, genetics and microbiology. Such skills are provided by the courses of the first year.

B) Teaching Units

Module 1 –General plant pathology (5 CFU):

1. Pathogenesis and disease (total teaching unit 8 hours)

1.1 Historical insights and definitions

Major achievements of the plant pathology history. Definitions and specific terms to be used in plant pathology. Disease triangle and pyramid. Koch’s postulates.

1.2 Pathogenesis

Parasitism and saprophytism. Biotrophic and necrotrophic pathogens. Disease cycle; inoculation, penetration, colonization, reproduction egression. Primary and secondary cycle. Symptoms.

Knowledge acquired in the teaching unit 1:

• Student knows the specific terms to be used during disease description. He/She knows the disease cycle phases and specificity of the different type of pathogen.

2. Pathogens (total teaching unit 20 hours)

2.1 Fungi

Structural, biochemical morphological feature of fungal cell with respect to the main fungi and oomycetes classes; Micelium and hyphae; hyphal modification; growth, nutrition and reproduction. Classification. Life cycle feature of fungi and omycetes classes. Infection mode: penetration, colonization, quiescence. Fungal diseases symptoms. Identification and diagnosis.

2.2 Bacteria

Structural, biochemical morphological feature of bacterial cell with respect to systematic classification. Infection mode: dissemination, penetration, quorum sensing. Types of bacteriosis (parenchimal, vascular and mixed). Main symptoms, Identification and diagnosis.

2.3 Mollicutes

Phytoplasms and Spiroplasms. Cellular features. Insights on the reproduction and infection modes.

2.4 Viruses

Hystorical insights, structural and molecular features, Classification and taxonomy. Symptoms. Infection cycle: replication, transmission with vectors. The Polymyxa case. Identification and diagnosis.

Knowledge acquired in the teaching unit 2:

• Student knows the main types of pathogens of plants and their infection characteristics, their cellular structure, growth, nutrition and reproduction and their taxonomic organization. She/he recognizes the main types of symptoms.

3. Plant resistance (total teaching unit 6 hours)

3.1. Innate Immunity

Resistance types: – Preformed and induced, structural and biochemical resistance. ROS and oxidative stress. Phenolic compounds.

3.2. Plant –pathogen recognition and resistance.

Host and non-host resistance. – Zig-zag model. Molecular recognition and signal transmission, Gene x gene theory and co-evolution. Stability and durability of resistance.

Knowledge acquired in the teaching unit 3:

• Student knows the main types of plant resistance, the genetic bases, the molecular mechanisms and the necessary signals for activation.

4. Abiotic stress (total teaching unit 3 hours)

Abiotic stress importance and classification – Recognition and symptoms – Adaptability and acclimation.

Thermal stress – Thresholds. Cold stress: cellular mechanisms and reversibility. Symptoms. Heat stress. Symptoms.

Water stress – Nutritional stresses - Other stresses – Symptoms

Knowledge acquired in the teaching unit 4:

• Student knows the main abiotic stress and the mechanisms associated to the cold stress development. She/he recognizes the main stress symptoms.

• 5. Mycotoxin (total teaching unit 3 hours)

  Biochemical features – Formulas, persistency and stability, toxicity mechanisms and thresholds.

  Fungi producing mycotoxins – Aspergillus, Penicillium, Fusarium, Claviceps.

  Knowledge acquired in the teaching unit 5:

• Student knows the main mycotoxins, the mechanisms of action and toxicity to humans and animals, the prevention and control actions.

6. Teaching support activity to Module 1 (total teaching unit 10 hours)

Laboratory activity (it will be divided in different turns)

This will be focused on two activities: i) demonstration of Koch’s postulates and ii) fungal pathogens recognition at optical microscope. For the first activity artificial infection on plant tissues will be performed using in vitro cultivated fungal inoculum. The developed symptoms will be observed in the subsequent turn and the pathogen will be re-isolated in vitro. In the second activity, the student will prepare some slides of fungal material and observe the fungal structure in vitro. At the end of the unit, students will be invited to write a brief report.

Consolidation activity

This part of the course will be dedicated to the consolidation of the knowledge provided during the lessons, with particular attention to the needings raised by the students.

Modulo 2 – Practical activity (1 CFU):

The practical activities will take place at the laboratories and greenhouses of the Department of Agricultural Sciences, in one or more turns according to the number of students.

Laboratory activities:

A serological diagnostic test will be performed to specifically detect the presence of proteins produced by pathogens (viruses, bacteria or fungi) in a plant matrix. Plant samples will be "blinded" provided to the students who will perform all the important steps of the assay assisted by the teacher and other expert staff. The final results will be discussed and interpreted with the teacher.

Activity in the greenhouse:

A bioassay will be achieved for the detection of viral agents. The students will perform a mechanical inoculation of one or more viruses on appropriate test plants. The plant material will be provided by the teacher or, alternatively, may be procured by students. These results will be interpreted by students led by the teacher

Knowledge acquired in the module 2:

The student knows the practical and applied aspects of two important diagnostic methods, such as DAS-ELISA and biological assay, to detect the presence of pathogens. He can interpret the results obtained.

Readings/Bibliography

All the material used during the lessons will be distributed online.

Books:

Belli, ‘Patologia Vegetale’, 2012, PICCIN editore, Padova.

Agrios, ‘Plant Pathology’, 2004, ELSEVIER Academic Press editore

Teaching methods

1. Class lectures: through the class lectures the student will acquire the knowledge necessary to understand the general characters of plant pathogens and the resistance forms of plants. This knowledge will be monitored during the course through a continuous interaction between teacher and student. This will possibly involve also the discussion of some interesting papers on the main topics covered during the lessons. This will allow to stimulate the critical sense communication skills of the student.
2. Practical activity: the student will be directly involved in general practices commonly used in a laboratory of plant pathology in order to practically apply the theoretical knowledge acquired during lessons.
3. Guided tours: student will be accompanied in guided tours to the agricultural field of DISTAL, in Cadriano and in local farms in order to examine plant diseases symptoms.

Assessment methods

The exam of general plant pathology will be carried out together with the exam of specific plant pathology. This will be done through written or oral exams on the topics covered during the course. In particular written exams (at least two per year) and oral ones (at least five per year). The written exam consist of 30 closed questions of general and of 30 closed question of specific plant pathology, plus 4 open questions. In the oral examination the student will be evaluated on at least six questions on the covered topic of the two general and specific plant pathology courses. The academic board will evaluate the scores of each learning subject, making a weighed mean of them (5 CFU general plant pathology, 1 CFU practical activity, 3 CFU specific plant pathology and 3 CFU defense) to express the final score.

Teaching tools

Overhead projector, personal computer and projector will be used for class lectures.

Laboratory exercises will take place in the teaching laboratories of BIO1 (first floor, via Fanin 44/46).

Office hours

See the website of Elena Baraldi

See the website of Claudio Ratti