User:Igriego11/Pathogenic fungus

Pathogenic fungi of plants are one of most common causes of plant disease and damage to crops. With over 100,000 known species, around only 10,000 can cause disease in plants. Compared to the 300 species of fungi that infect humans and animals. If you are looking for pathogenic fungi of humans and animals click here. Most of the pathogenic fungi belong to the phyla Ascomycota and Basidiomycota. Using spores that are produced through Sexual reproduction or Asexual reproduction spreading disease from one host to another. while some soil fungi can be Saprotrophic for part of their life cycle. pathogenic fungi start by invading the plant cells and either begin a Biotrophic lifestyle that colonizes living tissue and manipulates the plants metabolism to retrieve nutrients while keeping the plant alive. Or the fungi can become necrotrophic, Where once inside the plant cell begins to secrete a toxin that decays the plant tissue into available nutrients killing the plant in the process.

Pathogenic fungi and their diseases
Groups and species of fungi within the ascomycota and basidiomycota cause different diseases in plants. Some fungi are specific to a certain species or to only a certain part of a plant. While other fungi species like fusarium are more broad with their range of infection being able to infect many species or multiple parts of a plant. All start by penetrating the Cell wall, the plants first line of defense to allow colonization and infection. Fungi once inside colonizes the cell growing filamentous tubes of Hypha throughout. The virulence of the fungal pathogen depends on the ecological niche of the fungi infecting and the type of plant it is infecting. Infection also depends on host compatibility with pathogen using gene-for-gene resistance called Resistance (R) genes, that signals the plant to send out defensive responses. The function of the R gene is dependent on the genotype of the fungi/pathogen.

Ascomycota:

 * Botrytis cinerea (grey mold)
 * Erysiphales (Powdery mildew)
 * Fusarium (Fusarium ear blight, Panama disease)
 * Sclerotinia sclerotiorum ( cottony rot, Stem rot)
 * Magnaporthe grisea (Rice blast, pitting disease)
 * Verticillium (Verticillium wilt)



Basidiomycota

 * Armillaria (white root rot)
 * Phakopsora pachyrhizi (Soybean rust)
 * Puccinia (Rust)
 * Rhizoctonia (Brown patch, Sheath blight)
 * Ustilago (Smut)

Fungal like organisms that cause pathogens
Oomycetes were originally thought to be fungi due to their morphology and life cycle, as well as having similar ways of acquiring nutrition and similar ecological roles of "true fungi. Oomycetes are fungal like heterotrophs that live in marine, freshwater and terrestrial environments, having species that are plant pathogens that cause major economic damage to crops.

Oomycota

 * Pythium (Root rot)
 * Phytophthora (Sudden Oak Death, Downy mildew)

Sexual reproduction
When 2 multinucleate cells come together with their hyphael to reproduce. In ascomycota undergoes Meiosis creating many haploid spores that are released through ascospores that are meiotic. In Basidiomycota haploid spores are created in the Basidium and basidiocarp. Both types of fungi have rapid dispersal of spores into the environment allowing them to spread around rapidly. Sexual reproductions allows for new genes within the fungi to overcome plant resistance.

Asexual reproduction
Fungi cells undergo haploid nuclear division to create asexual spores called Conidia. These spores are often short lived but produced in mass amounts to ensure the dispersal of spores to new hosts where they can Germinate. Asexual reproduction allows for the benefit of not needing a mate to pass on spores to a new host. The negative affect of asexual reproduction of the fungi is it does not allow new genes to overcome the plants resistance to the pathogen.

Economic Damage
Diseases fro plant pathogens have caused major economic toll to agriculture causing $21 billion in damage to crops in the United states alone annually. With black stem rust of wheat being reoccurring and causing damage every year. Historically fungal diseases in plants have devastated crops such as Panama disease in Bananas that saw the end of the Gros Michel banana cultivar which was the main banana type until the 1950s. Panama Disease in Honduras led to a loss of 30,000 Hectare s from 1940 to 1960 with each hectare costing around $2,000 to $5,000 to plant. While other diseases are monitored to reduce the risk of an outbreak to crops such as soybean rust which was found in the United states for the first time in 2004 estimating if an Disease outbreak occurred losses annually would be $240 million to $2 billion in the United States.