Curtobacterium flaccumfaciens

Curtobacterium flaccumfaciens is a Gram-positive bacterium that causes disease on a variety of plants.[1] 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 pathovars, which help to better describe the pathogen.[2]

Curtobacterium flaccumfaciens
Scientific classification
Domain:	Bacteria
Phylum:	Actinobacteria
Class:	Actinobacteria
Order:	Actinomycetales
Family:	Microbacteriaceae
Genus:	Curtobacterium
Species:	C. flaccumfaciens
Binomial name
Curtobacterium flaccumfaciens (Hedges 1922) Collins and Jones 1984
Synonyms
Bacterium flaccumfaciens Hedges 1922 Phytomonas flaccumfaciens (Hedges 1922) Bergey et al. 1923 Pseudomonas flaccumfaciens (Hedges 1922) Stevens 1925 Corynebacterium flaccumfaciens subsp. flaccumfaciens (Hedges 1922) Dowson 1942 Corynebacterium betae Keyworth et al. 1956 Corynebacterium flaccumfaciens subsp. betae (Keyworth et al. 1956) Carlson and Vidaver 1982 Corynebacterium oortii Saaltink and Maas Geesteranus 1969 Corynebacterium flaccumfaciens subsp. oortii (Saaltink and Maas Geesteranus 1969) Carlson and Vidaver 1982 Corynebacterium poinsettiae (Starr and Pirone 1942) Burkholder 1948 Corynebacterium flaccumfaciens subsp. poinsettiae (Starr and Pirone 1942) Carlson and Vidaver 1982 Corynebacterium flaccumfaciens (Hedges 1922) Dowson 1942

Hosts and symptoms

Curtobacterium flaccumfacien is a bacterial wilt pathogen. The hallmark symptoms of bacterial wilt are leaf and petiole wilting. Chlorosis 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.[3] 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.[4] 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).[5] 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.[6]

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, humidity, and soil 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.[7] For example, Curtobacterium flaccumfaciens pv. oortii survive in the vegetative propagative organs (bulbs) rather than in the seeds, like Curtobacterium flaccumfaciens pv. flaccumfaciens.[8]

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.[9] 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 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.[10]

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, is a beginners diagnostic tool used to identify this bacterium.[11] Bacteria may be detected beneath the seedcoat 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.[12] 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 procedure. There is little resistance available commercially to Curtobacterium flaccumfaciens pv. flaccumfaciens and antibiotics are ineffective.[13]

See also

• List of soybean diseases

References

1. Michelle J. Francis; Richard R. Doherty; Minoo Patel; John F. Hamblin; Samar Ojaimi; Tony M. Korman (2 May 2011). "Curtobacterium flaccumfaciens Septic Arthritis following Puncture with a Coxspur Hawthorn Thorn". Journal of Clinical Microbiology. 49 (7): 2759–2760. doi:10.1128/JCM.00340-11. PMC 3147839. PMID 21562106.
2. George N. Agriosrman (October 9, 2005). Agrios g.n. 2005. plant pathology 5th edition. Academic Press, New York, USA.
3. U.F. Sammer; K. Reiher (2012). "Curtobacterium flaccumfaciens pv. flaccumfaciens on Soybean in Germany–A Threat for Farming". Journal of Phytopathology. 160 (6): 314–316. doi:10.1111/j.1439-0434.2012.01902.x.
4. R. M. Harveson; H. F. Schwartz; U. Mazzucchi (2007). "Bacterial diseases of dry edible beans in the Central High Plains". Plant Health Prog. 8: 35. doi:10.1094/PHP-2007-0125-01-DG.
5. C. Allen; P. Prior; A.C. Hayward (2005). Bacterial wilt disease and the Ralstonia solanacearum species complex. American Phytopathological Society.
6. M.J. Davis (1986). "Taxonomy of plant-pathogenic coryneform bacteria". Annual Review of Phytopathology. 24 (1): 115–140. doi:10.1146/annurev.phyto.24.1.115.
7. T. S. Júnior; D. R. Negrão; A. T. Itako; J. M. Soman; A. C. Maringoni (2012). "Survival of Curtobacterium Flaccumfaciens pv. Flaccumfaciens in Soil and Bean Crop Debris". Journal of Plant Pathology. 94 (2): 331–337.
8. C. Allen; P. Prior; A.C. Hayward (2005). Bacterial wilt disease and the Ralstonia solanacearum species complex. American Phytopathological Society.
9. George N. Agriosrman (October 9, 2005). Agrios g.n. 2005. plant pathology 5th edition (PDF). Academic Press, New York, USA. Retrieved 4 December 2016.
10. P. R. Miller; H. L. Pollard (1976). Multilingual compendium of plant diseases. American Phytopathological Society.
11. George N. Agriosrman (October 9, 2005). Agrios g.n. 2005. plant pathology 5th edition. Academic Press, New York, USA.
12. A. Calzolari; M. Tomesani; U. Mazzucchi (1987). "Comparison of immunofluorescence staining and indirect isolation for the detection of Corynebacterium flaccumfaciens in bean seeds". EPPO Bulletin. 17 (2): 157–163. doi:10.1111/j.1365-2338.1987.tb00021.x.
13. OEPP/EPPO (1982). "Data sheets on quarantine organisms No. 48, Corynebacterium flaccumfaciens". Bulletin OEPP/EPPO Bulletin. 12 (1).