PLANTS AND FUNGI

ENZYMES

PROBLEM

ENZYMES THAT ARE IN FUNGI

CAUSE DAMAGES ON THE CELULAR WALL OF PLANTS

Why is plant pathology important?

Food quantity

Food quality

Agronomic practices – tillage, pesticide use

Diversity and stability of ecosystems

beauty

Fungal pathogenicity on plants

Plant pathogens can be biotrophic (rusts and smuts) or necrotrophic (opportunistic)

Necrotrophs can display high levels of host specificity, e. g. Magnaporthe grisea

Saprotroph“Weak”Facultative parasite

Necrotroph“Strong”Facultative parasite

BiotrophObligate parasite

Increasing specialization Increasing host range

When a living organism's cells or tissues die or degenerate, the condition is called necrosis. In a plant, necrosis causes leaves, stems and other parts to darken and wilt. Necrosis weakens the plant and makes it more susceptible to other diseases and pests. Some plant diseases caused by a specific agent have the word "necrosis" in their name, such as tomato pith necrosis. However, necrosis is typically considered a symptom rather than a disease.

Symptom types -- Necrosis

Symptom types -- necrosis

Blumeriella on plum Alternaria solani – early blight of potato

Refers to the loss of rigidity of non-woody parts of plants. This occurs when the turgor pressure in non-lignified plant cells falls towards zero, as a result of diminished water in the cells. The rate of loss of water from the plant is greater than the absorption of water in the plant. The process of wilting modifies the leaf angle distribution of the plant (or canopy) towards more erectophile conditions.

Symptom types – Wilt

Symptom types – Wilt

Ophiostoma novo-ulmi

Panama disease: Fusarium oxysporum f.sp. cubense

Symptom types – Hormone Induced

Fusarium moniliforme = Gibberella fujikuroi gibberellins

Etiolation Bakanae of rice

Symptom types – Hormone Induced

Taphrina deformans

Synchytrium endobioticum

Abscission (from the Latin ab, meaning away, meaning to cut)

It is a term used in several areas of biology to mean shedding of various parts of an organism.

In plant sciences, it most commonly refers to the process by which a plant drops one or more of its parts, such as a leaf, fruit, flower, or seed.

Symptom types – Abscission

Symptom types – Abscission

Hemileia vastatrix

Symptom types – sterilization

Claviceps purpurea – ergot

Ustilago maydis

Interactions between Plants and their Pathogens

In humans, the skin forms the first line of defense against infection. In plants, this outer defense layer is the cuticle, a layer of waxy material above the epidermis. This stops many would-be plant pathogens from getting in on the act.

However, there is a weak spot in the plant’s defense. In order to exchange carbon dioxide and oxygen for photosynthesis, plants have pores on their leaf surface called stomata. These pores are ideal back-door entrances for fungal pathogens to get in.

Other fungi have an enzyme called CUTINASE which seems to cut up the cuticle so the fungi can get in.

Top view (point to activate).

Side view (point to activate).

the next lines of defence are molecules called phytoanticipins. These are ready-made and act in a general way against the fungi.

an example of a phytoanticipin is the saponin, this is found in tomatoes, and is toxic to most fungal pathogens, as it mixes with the fats in fungal cell membranes and causes the cells to leak.

But fungi have a massive biochemical toolkit, and some fungi have developed an enzyme that can break down the saponin and as a result, they can grow on the plants.

Interactions between Plants and their Pathogens

The next part of the plant’s defense against fungi is structural. Plant cell walls are characterized by being rigid, and full of cellulose and other polysaccharides.

When a plant is infected by a fungus that grows as hyphae the cell wall can thicken dramatically to form a papilla, which grows around the invading hyphae, preventing them from going any further.

However, the fungi have enzymes capable of breaking down the cellulose-based papillae, so plants often add lignin, the brown wood polymer. This is difficult for most fungi to break down, as many decomposer fungi know. Lignin is made of many phenolic compounds, similar to the type we use as antiseptics, and these tend to saturate the area around the invading fungus, often killing it.

Interactions between Plants and their Pathogens

The plant produce molecules called phytoalexins.

These molecules often act in a similar way to antibiotics, by inhibiting fungal enzymes and blocking the synthesis of important molecules in the invading fungus.

Some phytoalexins however activate some of the host’s own enzymes, such as CHITINASE, which breaks down the fungal cell wall.

Interactions between Plants and their Pathogens

Host resistance and basic compatibility

Most plants are not attacked by the vast majority of potential pathogens

Preformed defenses Potential pathogens secrete chemicals

during growth that can be detected

How to fight fungal crops

Using:• The non-systemic fungicides or

contact • Systemic fungicides • Bacteria to protect crops from

fungal

Using -- Fungicides

Fungicides are biocidal chemical compounds or biological organisms used to kill or inhibit fungi or fungal spores.

Fungi can cause serious damage in agriculture, resulting in critical losses of yield, quality, and profit.

Fungicides are used both in agriculture and to fight fungal infections in animals.

Chemicals used to control oomycetes, which are not fungi, are also referred to as fungicides as oomycetes use the same mechanisms as fungi to infect plants.

Using – Fungicides – Non-Systemic fungicides or contact

The no contact or systemic fungicides remain on the surface of the sheet and drop the fungal spores can not 'sprout', introduced into it.

Should always be applied before symptoms appear, in seasons with favorable conditions for infection to occur, often with high humidity and mild temperatures.

If the fungus has entered (infected), these products do not do anything because they are preventive.

Using – Fungicides – Non-Systemic fungicides or contact

Using – Fungicides – Systemic fungicides

Systemic fungicides, unlike contact fungicides ,not remain on the surface of the sheet; but penetrate into the plant and, because of sap, are distributed within.

It has curative effects occur after infection.

Using – Fungicides – Systemic fungicides

Effectiveness of certain bacteria to protect crops from fungi, what and how they act.

Wheat is one of the most important crops worldwide. It has been part of global economic development and is, par excellence, the most widely cultivated cereal.

A recent study published by the U.S. Agricultural Research Service (ARS) found that a number of bacteria could help protect crops from wheat and barley of possible pests and plant ills. There are a number of bacteria that benefit from plant roots of wheat and barley for its development.

In addition, these bacteria could also be beneficial to protect these crops, as reported by U.S. specialists. The research focuses on the potential of bacteria to control the growth of decay-causing fungi in the roots of wheat and barley plants

The bacteria responsible

The main function is to prevent bacterial growth in two kinds of fungi, Pythium and Rhizoctonia

The benefits associated with these bacteria in plants are of the genus Pseudomonas and a total of 11 strains are included. The main function is to prevent bacteria growth of two kinds of fungi, Pythium and Rhizoctonia, primarily responsible for diseases in wheat and barley. These two fungi are able to grow in moist, cool soils without involving a problem

Role of bacteria

Bacteria with the ability to prevent fungal growth (Pseudomonas) may secrete enzymes and different biochemical with great power to help keep in check the growth of fungi. Also, some strains of this bacterium helping plants to protect themselves and stimulating an immune response against external adverse problems. Also help produce substances similar to hormones that stimulate the growth of both shoot and root, something that helps the plant to overcome the damage caused by fungi possible.

Results For the study,

greenhouse tests were made using five different strains of bacteria and the results show a significant reduction, from 50% to 92% of the rot caused by the fungus. It has studied both the wheat and barley. In both cases, the response has been excellent.

RESULTS In fungal plant pathogenesis, enzymes are playing a crucial role and

they are involved in the external and internal interactions. To restrict the development of fungal pathogens, the plants formed many defense mechanisms. They built mechanical barriers from lignin, suberin, callose and produced a lot of antimicrobial compounds with low molecular weight like phenols, alkaloids and others. Enhanced production of some enzymes and their activity increasing is one of the most important processes in plant defense. These enzymes occur frequently in many isoforms and are involved in synthesis of defense substances or have a direct antimicrobial activity.

Most natural fungicides are just as effective as chemical pesticides and fungicides but don’t have the risks that are associated with chemical products. While chemical fungicides and pesticides may be the most effective pest control for farmers, experts agree that whenever possible you should use natural pest control methods to minimize the health risks to you, your family, your neighbors, and your pets.