''Curtobacterium flaccumfaciens'' is a

Gram-positive In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. Gram-positive bac ...

bacterium Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were a ...

that causes disease on a variety of

plant Plants are predominantly Photosynthesis, photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all curr ...

s. Gram-positive bacterium characteristics include small irregular rods, lateral flagella, the ability to persist in aerobic environments, and cells containing catalase. In the interest of studying pathogenicity in plants, the species ''Curtobacterium flaccumfaciens'' is broken down further into

pathovar A pathovar is a bacterial strain or set of strains with the same or similar characteristics, that is differentiated at infrasubspecific level from other strains of the same species or subspecies on the basis of distinctive pathogenicity to one o ...

s, which help to better describe the pathogen.

Hosts and symptoms

''Curtobacterium flaccumfacien'' is a bacterial wilt pathogen. The hallmark symptoms of bacterial wilt are leaf and petiole wilting.

Chlorosis In botany, chlorosis is a condition in which leaves produce insufficient chlorophyll. As chlorophyll is responsible for the green color of leaves, chlorotic leaves are pale, yellow, or yellow-white. The affected plant has little or no ability to ...

of the leaf and tissue occurs due to the lack of water transport. ''Curtobacterium flaccumfaciens'' as a species has a wide host range not limited to kidney beans, soybeans, tulips, and tomatoes. However, the species is artificially separated into a pathovar based on host range and symptoms. One of the economically important pathovars is ''Curtobacterium flaccumfaciens'' pv. ''flaccumfaciens''. This pathovar is classified as bacterial wilt and has a primary host range of the genus ''Phaseolus'' (beans), but the pathogen can infect many other species of the ''Fabaceae''. In beans the symptoms can be devastating to the crop yield. These beans have severe foliage wilting and chlorosis. One ornamental example is ''Curtobacterium flaccumfaciens'' pv. ''oortii''. The primary host are plants from the genus ''Tulipa'' (Tulip). Although the host range differs, the symptoms are relatively similar. During flowering typical symptoms of dehydration are observed. Similarly to beans, the tulips get wilt. In severe cases, the plant eventually fails to recover from wilting and dies.

Disease cycle

Survival ''Curtobacterium flaccumfaciens'' can overwinter in plant debris, diseased plants, wild hosts, seeds, or vegetative propagative organs. The bacteria can survive only a couple of weeks as free bacteria in soil. Multiple factors go into survival of a bacterial population, including

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied on ...

humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity dep ...

, and

soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former ...

characteristics. Infected seeds cannot be used for susceptible bean crops because ''Curtobacterium flaccumfaciens'' pv. ''flaccumfaciens'' has been known to survive in dried bean pods from five years and up to 24 years in laboratory conditions. Different pathovars survive in slightly different ways. For example, ''Curtobacterium flaccumfaciens'' pv. ''oortii'' survive in the vegetative propagative organs (bulbs) rather than in the seeds, like ''Curtobacterium flaccumfaciens'' pv. ''flaccumfaciens''. Dispersal ''Curtobacterium flaccumfaciens'' causes wilting at high populations and disperses in many ways. The bacteria multiply relatively quickly which increases the possibility that ''Curtobacterium flaccumfaciens'' can shed from dying or dead plant material. The pathogen is normally dispersed via agricultural practices such as, planting saved seed and through farm equipment. In the case of beans & tulips these practices move the

propagule In biology, a propagule is any material that functions in propagating an organism to the next stage in its life cycle, such as by dispersal. The propagule is usually distinct in form from the parent organism. Propagules are produced by organisms ...

during overwriting phase of their life cycles. This is effective dispersal for the pathogen. Infection ''Curtobacterium flaccumfaciens'' usually enters the plant though a wound. Natural wounds (created by excision of flowers or genesis of lateral roots) and unnatural wounds could become entry sites. There are no reports of vectors, but the nematode ''Meloidogyne incognita'' may assist entry by providing unnatural wounds.

Management

Management varies for each between hosts. For this purpose, we will look specifically at the detection and control methods of ''Curtobacterium flaccumfaciens'' pv. ''flaccumfaciens''. Since most plant pathogens are Gram-negative detection of Gram-positive bacterium, using methods such as the

KOH test The KOH Test for ''Candida albicans'', also known as a potassium hydroxide preparation or KOH prep, is a quick, inexpensive fungal test to differentiate dermatophytes and ''Candida albicans'' symptoms from other skin disorders like psoriasis and e ...

, is a beginners diagnostic tool used to identify this bacterium. Bacteria may be detected beneath the

seedcoat A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiosperm p ...

by means of a combined cultural and slide agglutination test. Bean seed from countries where the disease is known to occur should be inspected for discoloration of the seedcoat. Immunofluorescence staining can also be used to detect the bacterium in contaminated seed lots. Control may be affected by using disease-free seed and crop rotations. Seeds grown in dry climates are usually free from infection and are, therefore, recommended for distribution. The strongest control regulations handed down by the European and Mediterranean Plant Protection (EPPO) to date was a

quarantine A quarantine is a restriction on the movement of people, animals and goods which is intended to prevent the spread of disease or pests. It is often used in connection to disease and illness, preventing the movement of those who may have been ...

procedure. There is little resistance available commercially to ''Curtobacterium flaccumfaciens'' pv. ''flaccumfaci''ens and antibiotics are ineffective.

References

External links

* {{Taxonbar, from=Q5196014 Microbacteriaceae Soil biology Soybean diseases

Hosts and symptoms

Disease cycle

Management

See also

References

External links