Rusts are plant diseases caused by pathogenic fungi of the order Puccini ales (previously known as Ordinals). An estimated 168 rust genera and approximately 7,000 species, more than half of which belong to the genus Puccini, are currently accepted.
Rust fungi are highly specialized plant pathogens with several unique features. Taken as a group, rust fungi are diverse and affect many kinds of plants.
However, each species has a very narrow range of hosts and cannot be transmitted to non-host plants. In addition, most rust fungi cannot be grown easily in pure culture.
A single species of rust fungi may be able to infect two different plant hosts in different stages of its life cycle, and may produce up to five morphologically and biologically distinct spore-producing structures viz., spermatogonia, AECID, Medina, Celia, and basilica in successive stages of reproduction. Each spore type is very host specific, and can typically infect only one kind of plant.
Infections begin when a spore lands on the plant surface, germinates, and invades its host. Infection is limited to plant parts such as leaves, petioles, tender shoots, stem, fruits, etc.
Rust fungi grow intracellularly, and make spore-producing fruiting bodies within or, more often, on the surfaces of affected plant parts. Some rust species form perennial systemic infections that may cause plant deformities such as growth retardation, witch's broom, stem canker, galls, or hypertrophy of affected plant parts.
The Roman agricultural festival Regalia (April 25) has ancient origins in combating wheat rust. Rusts are considered among the most harmful pathogens to agriculture, horticulture and forestry.
Rust fungi are major concerns and limiting factors for successful cultivation of agricultural and forest crops. All rusts are obligate parasites, meaning that they require a living host to complete their life cycle.
They generally do not kill the host plant but can severely reduce growth and yield. Cereal crops can be devastated in one season; oak trees infected in the main stem within their first five years by the rust Consortium Quercus often die.
These serve mainly as non-repeating, eukaryotic, asexual spores, and go on to infect the primary host. They are often profuse, red / orange, and a prominent sign of rust disease.
They usually do not infect a plant directly; instead they germinate to produce basilica and basidiospores. These wind borne haploid spores often infect the alternate host in Spring.
In macro cyclic and tricyclic life cycles, the rust may be either host alternating (heterogeneous) (i.e., the aerial state is on one kind of plant but the tell state on a different and unrelated plant), or non-host alternating (autonomous) (i.e., the aerial and tell states on the same plant host). This can be contrasted with an autonomous fungus which can complete all parts of its life cycle on a single host species.
Understanding the life cycles of rust fungi allows for proper disease management. There are definite patterns of relationship with host plant groups and the rust fungi that parasitize them.
Some genera of rust fungi, especially Puccini and Produces, comprise species that are capable of parasitizing plants of many families. The spores of rust fungi may be dispersed by wind, water or insect vectors.
A rust spores typically germinates on a plant surface, growing a short alpha called a germ tube. This germ tube may locate a stoma by a touch responsive process known as thigmotropism.
This involves orienting to ridges created by epidermal cells on the leaf surface, and growing directionally until it encounters a stoma. From the underside of an appressorium, a slender alpha grows downward to infect plant cells It is thought that the whole process is mediated by stretch-sensitive calcium ion channels located in the tip of the alpha, which produce electric currents and alter gene expression, inducing appressorium formation.
An iron and phosphorus rich neck band bridges the plant and fungal membranes in the space between the cells for water flow, known as the apples, thus preventing the nutrients reaching the plant's cells. The fungus continues growing, penetrating more and more plant cells, until spore growth occurs.
The process repeats every 10 – 14 days, producing numerous spores that can be spread to other parts of the same plant, or to new hosts. The control methods of rust fungus diseases depend largely on the life cycle of the particular pathogen.
Macro cyclic Disease : Developing a management plan for this type of disease depends largely on whether the repeating stage (urediniospores) occur on the economically important host plant or the alternate host. Removal of the alternate host disrupts the life cycle of the rust fungi Consortium ridicule, preventing the formation of basidiospores which infect the primary host.
Infected tissue is removed from white pines and strict quarantines of Tribes SPP. Puccini grains is a macro cyclic heterogeneous fungus that causes wheat stem rust disease.
The repeating stage in this fungus occurs on wheat and not the alternate host, barberry. The repeating stage allows the disease to persist in wheat even though the alternate host may be removed.
Although the disease cannot be stopped by removal of the alternate host, the life cycle is disrupted and the rate of mutation is decreased because of reduced genetic recombination. This allows resistance bred crops to remain effective for a longer period of time.
Tricyclic Disease : Because there is no repeating stage in the life cycle of tricyclic fungi, removal of the primary or the alternate host will disrupt the disease cycle. Cedar-apple rust disease, for example, can persist despite removal of one of the hosts since spores can be disseminated from long distances.
Some organic preventative solutions are available and sulfur powder is known to stop spore germination. High standards of hygiene, good soil drainage, and careful watering may minimize problems.
Any appearance of rust must be immediately dealt with by removing and burning all affected leaves. Composting, or leaving infected vegetation on the ground will spread the disease.
The process is expensive and fungicide application is best reserved for seasons when foliar diseases are severe. Research indicates, the higher the foliar disease severity, the greater the return from the use of fungicides.
Southern rust's distinguishing characteristic is that pustules form mostly on the upper leaf surface and spores are more orange. Southern rust spreads more quickly and has a higher economic impact when hot, humid weather conditions persist.
High moisture levels may exacerbate rust disease symptoms. The avoidance of overhead watering at night, using drip irrigation, reducing crop density, and using fans to circulate air flow may decrease disease severity.
For example; Puccini anti infects the flowering plant cockle bur (Anthem). Recently, a total of 95 rust fungi belonging to 25 genera associated with 117 forest plant species belonging to 80 host genera under 43 host families were reported from the Western Ghats, Kerala, India.
Rust fungus, Puccini urticaria on the surface of a nettle leaf Utopia Antique: Readings of the Golden Age and Decline at Rome.
^ Dating, H.B., S. Werner, and M. Berlitz, The role of fungal oppressors in plant infection. ^ Zhou, X.L., et al., A mechanosensitive channel in whole cells and in membrane patches of the fungus Produces.
“The Genetics and Expression of Resistance in Plants to Rusts of the Genus Puccini”. “Fine Mapping of Ur-3, a Historically Important Rust Resistance Locus in Common Bean”.
White Pine Blister Rust : Consortium ridicule . Â From the term oxidation, â€ one can assume that oxygen is involved in the process of rust formation.
Â And, true enough, oxygen is the main chemical that sort of initiates the formation of rust on metals. Â And when this happens, iron will react in a way that rust will form on many parts of its surface.
Â This is the simple reason that people always associate rust with a reddish color. Â There are other metals that are quite resistant to oxidation, and so they do not rust easily.
Â But in the strictest sense, rust could actually form in a different color. But since the most commonly used metal is iron, most rust that people see is reddish.