Fusarium

obmar · Site Admin Joined: 14 Apr 2006 Posts: 5697

Fusarium oxysporum
wilts, rots, stem decay...
Hosts Distribution Symptoms Biology Epidemiology Management Reference

Authors

Andre K. Gonsalves, Educational Specialist

Stephen A. Ferreira, Extension Plant Pathologist

Department of Plant Pathology, CTAHR

University of Hawaii at Manoa

HOSTS

In Hawaii, hosts of Fusarium oxysporum include: potato, sugarcane, garden bean, cowpea, Prickly pear, cultivated zinnia, pansy, Assam rattlebox, Baby's breath, and Musa sp. (Raabe et al., 1981).

Like various other plant pathogens, Fusarium oxysporum has several specialized forms - known as formae specialis (f.sp.) - that infect a variety of hosts causing various diseases. In Hawaii, these include: Fusarium oxysporum f.sp. asparagi (fusarium yellows on asparagus); f.sp. callistephi (wilt on China aster); f.sp. cubense (Panama disease/wilt on banana); f.sp. dianthi (wilt on carnation); f.sp. koae (on koa); f.sp. lycopersici (wilt on tomato); f.sp. melonis (fusarium wilt on muskmelon); f.sp. niveum (fusarium wilt on watermelon); f.sp. pisi (on edible-podded pea); f.sp. tracheiphilum (wilt on Glycine max); and f.sp. zingiberi (fusarium yellows on ginger) (Raabe et al., 1981).

DISTRIBUTION

Overall, the distribution of Fusarium oxysporum is known to be COSMOPOLITAN. However, the different special forms (f.sp.) of F. oxysporum often have varying degrees of distribution.

SYMPTOMS

Fusarium oxysporum and its various formae speciales have been characterized as causing the following symptoms: vascular wilt, yellows, corm rot, root rot, and damping-off. The most important of these is vascular wilt. Of the vascular wilt-causing Fusaria, Fusarium oxysporum is the most important species (Agrios, 1988; Smith et al., 1988). Strains that are rather poorly specialized may induce yellows, rot, and damping-off, rather than the more severe vascular wilt (Smith et al., 1988).

Since fusarium wilt is the most important disease caused by F. oxysporum, the focus of this section will be on this symptom. In general, fusarium wilts first appear as slight vein clearing on the outer portion of the younger leaves, followed by epinasty (downward drooping) of the older leaves. At the seedling stage, plants infected by F. oxysporum may wilt and die soon after symptoms appear. In older plants, vein clearing and leaf epinasty are often followed by stunting, yellowing of the lower leaves, formation of adventitious roots, wilting of leaves and young stems, defoliation, marginal necrosis of remaining leaves, and finally death of the entire plant (Agrios, 1988). Browning of the [vascular tissue] is strong evidence of fusarium wilt. Further, on older plants, symptoms generally become more apparent during the period between blossoming and fruit maturation (Jones et al., 1982; Smith et al., 1988).

BIOLOGY

In solid media culture, such as potato dextrose agar (PDA), the different special forms of F. oxysporum can have varying appearances. In general, the aerial mycelium first appears white, and then may change to a variety of colors - ranging from violet to dark purple - according to the strain (or special form) of F. oxysporum. If sporodochia are abundant, the culture may appear cream or orange in color (Smith et al., 1988).

F. oxysporum produces three types of asexual spores: microconidia, macroconidia, and chlamydospores (Agrios, 1988). [Microconidia] are one or two celled, and are the type of spore most abundantly and freqeuntly produced by the fungus under all conditions. It is also the type of spore most frequently produced within the vessels of infected plants. [Macroconidia] are three to five celled, gradually pointed and curved toward the ends. These spores are commonly found on the surface of plants killed by this pathogen as well as in sporodochialike groups. [Chlamydospores] are round, thick-walled spores, produced either terminally or intercalary on older mycelium or in macroconidia. These spores are either one or two celled (Agrios, 1988).

DISEASE CYCLE

F. oxysporum is an abundant and active saprophyte in soil and organic matter, with some specific forms that are plant pathogenic (Smith et al., 1988). Its saprophytic ability enables it to survive in the soil between crop cycles in infected plant debris. The fungus can survive either as mycelium, or as any of its three different spore types (Agrios, 1988).

Healthy plants can become infected by F. oxysporum if the soil in which they are growing is contaminated with the fungus. The fungus can invade a plant either with its sporangial germ tube or mycelium by invading the plant's roots. The roots can be infected directly through the root tips, through wounds in the roots, or at the formation point of lateral roots (Agrios, 1988). Once inside the plant, the mycelium grows through the root cortex intercellulary. When the mycelium reaches the xylem, it invades the vessels through the xylem's pits. At this point, the mycelium remains in the vessels, where it usually advances upwards toward the stem and crown of the plant. As it grows, the mycelium branches and produces microconidia, which are carried upward within the vessel by way of the plant's sap stream. When the microconidia germinate, the mycelium can penetrate the upper wall of the xylem vessel, enabling more microconidia to be produced in the next vessel. The fungus can also advance laterally as the mycelium penetrates the adjacent xylem vessels through the xylem pits (Agrios, 1988).

Due to the growth of the fungus within the plant's vascular tissue, the plant's water supply is greatly affected. This lack of water induces the leaves' stomata to close, the leaves wilt, and the plant eventually dies. It is at this point that the fungus invades the plant's parenchymatous tissue, until it finally reaches the surface of the dead tissue, where it sporulates abundantly (Agrios, 1988). The resulting spores can then be used as new inoculum for further spread of the fungus.

EPIDEMIOLOGY

F. oxysporum is primarily spread over short distances by irrigation water and contaminated farm equipment. The fungus can also be spread over long distances either in infected transplants or in soil. Although the fungus can sometimes infect the fruit and contaminate its seed, the spread of the fungus by way of the seed is very rare (Agrios, 1988). It is also possible that the spores are spread by wind.

MANAGEMENT

Because F. oxysporum and its many special forms affect a wide variety of hosts, the management of this pathogen is discussed in more detail in the respective summaries. In general, some effective means of controlling F. oxysporum include: disinfestation of the soil and planting material with fungicidal chemicals, crop rotation with non-hosts of the fungus, or by using resistant cultivars (Jones et al., 1982; Agrios, 1988; Smith et al., 1988).

REFERENCES

Agrios, G.N. 1988. Plant Pathology, 3rd. ed. Academic Press, Inc.: New York. 803pp.

Farr, D.F., G.F. Bills, G.P. Chamuris, and A.Y. Rossman, eds. 1989. Fungi on plants and plant products in the United States. APS PRESS: St. Paul. 1252pp.

Jones, J.P., J.B. Jones, and W. Miller. 1982. Fusarium wilt on tomato. Fla. Dept. Agric. & Consumer Serv., Div. of Plant Industry. Plant Pathology Circular No. 237.

Raabe, R.D., I.L. Conners, and A.P. Martinez. 1981. Checklist of plant diseases in Hawaii: including records of microorganisms, principally fungi, found in the state. Hawaii Institute of Tropical Agriculture and Human Resources (CTAHR), Information Text Series 022. 313pp.

Smith, I.M., J. Dunez, D.H. Phillips, R.A. Lelliott, and S.A. Archer, eds. 1988. European handbook of plant diseases. Blackwell Scientific Publications: Oxford. 583pp.

NOVEMBER 1993

2A-FUOXY

obmar · Site Admin Joined: 14 Apr 2006 Posts: 5697

Fusarium Fungus

Fusarium fungus is regularly found in plant material and soil in tropical and subtropical areas. Without eye drop treatment, which can last two to three months, the infection can scar the cornea causing blindness. Symptoms may include blurry vision, pain or redness, increased sensitivity to light and excessive discharge from the eye.

Bausch & Lomb voluntarily suspended shipment of a contact lens solution after federal health officials linked it on April 10, 2006 to a fungal eye infection that can cause temporary blindness. Federal and state health officials have interviewed 30 of those patients. Of the 28 who wore soft contact lens, 26 reported using Bausch & Lomb's ReNu brand contact lens solution. The U.S. Centers for Disease Control and Prevention is watching the situation and said it has received reports of about 50 possible cases in 12 states this year so far.

The 109 U.S. cases the CDC is investigating involve infections from June 2005 to March and are from California, Connecticut, Florida, Georgia, Iowa, Maryland, Massachusetts, Michigan, Missouri, New Jersey, New York, North Dakota, Ohio, Pennsylvania, Tennessee, Texas and Vermont.

Singapore health officials noticed a spike in January and discovered 39 cases involving contact lens users from 2005 to February of this year. Cases have also been reported in Malaysia and Hong Kong.

To complicate matters further, the fungus is tricky to detect because diagnosis requires a lab culture not all doctors are prepared to take or read. And the fungus can be so slow-growing that it takes weeks for the culture to come back. The medicine used to treat fungal infections is not widely stocked by pharmacies and often must be ordered.

If you or a loved one wears contact lenses and you developed Fusarium fungus or any other injury as a result of Bausch & Lomb Renu MoistureLoc saline solution, contact Parker & Waichman, LLP for a free case evaluation. Call 1-800-LAW-INFO (1-800-529-4636) or fill out the short form at the right.

obmar · Site Admin Joined: 14 Apr 2006 Posts: 5697

New Pima Cottons Fight Fusarium Fungus
By Marcia Wood
February 25, 2008
Some of your favorite clothes, towels and sheets might be made with cotton, America's best-selling fabric. But cotton plants won't produce top yields of the fluffy white bolls if they're clobbered by a microbe known as FOV race 4, short for Fusarium oxysporum f.sp. vasinfectum.

Now, studies by Agricultural Research Service (ARS) scientist Mauricio Ulloa and cooperators may lead to new ways to combat the disease.

The Fusarium fungus can clog a plant's vascular system, or "plumbing," according to Ulloa. He's a geneticist at the ARS Western Integrated Cropping Systems Research Unit in Shafter, Calif.

Already, Ulloa, ARS colleague Richard Percy at College Station, Texas, and Michael Davis and Robert Hutmacher of the University of California have developed four new kinds of Fusarium-resistant pima cotton plants. Pima cotton makes premium fabrics for clothing and home.

The scientists will offer these parent pimas, known as SJ-07P-FR01 through -FR04, to cotton breeders and researchers this year. The plants rank as the first publicly owned pimas that have good resistance to race 4; good-to-superior fiber length, which is important to fabric quality; and moderate yields, according to Ulloa.

Now the scientists are testing hundreds of upland cotton plants. Upland cotton offers excellent, less expensive fibers. And, in related studies, Ulloa and co-investigators are delving more deeply into cotton's genetic makeup.

The intent? To find markers—genetic material that indicates the presence of genes of potential interest. The scientists have already identified a significant number of markers that may prove to be indicators of Fusarium resistance.

Read more about this research in the February

The Inquisitor · Joined: 17 Jun 2006 Posts: 772

uh, what are you trying to tell us, obmar?

Have you come down with some strange disease that you'd now like to share with the world??

obmar · Site Admin Joined: 14 Apr 2006 Posts: 5697

I am looking into planting trees as a new venture
and these fungus will be needed to stimulate
the trees to produce stuffs that are highly priced
in the perfume industry.

I am expected to receive delivery of the
first batch of seedlings tomorrow.

Radiate_Truth · Joined: 18 Aug 2007 Posts: 1056

If it works out...
Send us some pictures.