Xylella fastidiosa
Encyclopedia
Xylella fastidiosa, a bacterium in the class Gammaproteobacteria
, is an important plant pathogen that causes phoney peach disease in the southern United States
, oleander leaf scorch, and Pierce's disease, and citrus variegated chlorosis disease (CVC) in Brazil
.
(its vector), native to the southeast United States, was discovered in the Temecula Valley in California in 1996. It triggered a unique effort from growers, administrators, policy makers and researchers to work together in finding a solution for this immense threat. No cure has yet been found, but the understanding of Xylella fastidiosa and glassy-winged sharpshooter biology have exponentially increased since 2000, when the California Department of Food and Agriculture, in collaboration with different universities, such as University of California, Davis; University of California, Berkeley, and University of California, Riverside, and University of Houston-Downtown started to focus their research on this pest. The research explores the different aspects of the disease propagation from the vector to the host plant and within the host plant, to the impact of the disease on California's economy. All researchers working on Pierce's disease meet annually in San Diego in mid-December to discuss the progress in their field. All proceedings from this symposium can be found on the Pierce's disease website, developed and managed by the Public Intellectual Property Resource for Agriculture (PIPRA).
There are no resistant Vitis vinifera
varieties, and Chardonnay
and Pinot noir
are especially sensitive, although muscadine
grapes have a natural resistance. Pierce's disease is presently found in the southeastern United States, Mexico, Costa Rica, and Venezuela, and possibly in other parts of Central and South America. There are isolated hot spots of the disease near creeks in Napa and Sonoma in northern California.
Currently, work is underway at U.C. Davis to breed PD resistance into Vitis vinifera. The first generation was 50% high quality vinifera genes, the next 75%, the third 87% and the fourth 94%. In the spring of 2007, seedlings that are 94% vinifera were planted.
When a vine becomes infected, the bacterium causes a gel to form in the xylem
tissue of the vine, preventing water from being drawn through the vine. Leaves on vines with Pierce's disease will turn yellow and brown, and eventually drop off the vine. Shoots will also die. After one to five years, the vine itself will die. The proximity of vineyards to citrus orchards compounds the threat, because citrus is not only a host for the sharpshooter eggs, but it is also a popular overwintering site for the insect. Likewise, oleander
, a common landscaping plant in California, serves as a reservoir for Xylella.
Oleander leaf scorch is a disease of landscape oleander
s (Oleander nerium) caused by a strain of X. fastidiosa which has become prevalent in California and Arizona, USA. The disease is transmitted by another sharpshooter (Homalodisca liturata), a leafhopper.
Footnotes
Gammaproteobacteria
Gammaproteobacteria is a class of several medically, ecologically and scientifically important groups of bacteria, such as the Enterobacteriaceae , Vibrionaceae and Pseudomonadaceae. An exceeding number of important pathogens belongs to this class, e.g...
, is an important plant pathogen that causes phoney peach disease in the southern United States
Southern United States
The Southern United States—commonly referred to as the American South, Dixie, or simply the South—constitutes a large distinctive area in the southeastern and south-central United States...
, oleander leaf scorch, and Pierce's disease, and citrus variegated chlorosis disease (CVC) in Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
.
Pierce's disease
Pierce's disease was discovered in 1892 by Newton B. Pierce (1856–1916; California's first professional plant pathologist) on grapes in California near Anaheim. It became a real threat to California's wine industry and overall economy when the glassy-winged sharpshooterGlassy-winged sharpshooter
The glassy-winged sharpshooter is a large leafhopper insect from the family Cicadellidae, similar to other species of sharpshooter.-Description:These sharpshooters are about in length...
(its vector), native to the southeast United States, was discovered in the Temecula Valley in California in 1996. It triggered a unique effort from growers, administrators, policy makers and researchers to work together in finding a solution for this immense threat. No cure has yet been found, but the understanding of Xylella fastidiosa and glassy-winged sharpshooter biology have exponentially increased since 2000, when the California Department of Food and Agriculture, in collaboration with different universities, such as University of California, Davis; University of California, Berkeley, and University of California, Riverside, and University of Houston-Downtown started to focus their research on this pest. The research explores the different aspects of the disease propagation from the vector to the host plant and within the host plant, to the impact of the disease on California's economy. All researchers working on Pierce's disease meet annually in San Diego in mid-December to discuss the progress in their field. All proceedings from this symposium can be found on the Pierce's disease website, developed and managed by the Public Intellectual Property Resource for Agriculture (PIPRA).
There are no resistant Vitis vinifera
Vitis vinifera
Vitis vinifera is a species of Vitis, native to the Mediterranean region, central Europe, and southwestern Asia, from Morocco and Portugal north to southern Germany and east to northern Iran....
varieties, and Chardonnay
Chardonnay
Chardonnay is a green-skinned grape variety used to make white wine. It is originated from the Burgundy wine region of eastern France but is now grown wherever wine is produced, from England to New Zealand...
and Pinot noir
Pinot Noir
Pinot noir is a black wine grape variety of the species Vitis vinifera. The name may also refer to wines created predominantly from Pinot noir grapes...
are especially sensitive, although muscadine
Muscadine
Muscadines are a grapevine species native to the present-day southeastern United States that has been extensively cultivated since the 16th Century. It differs from Vitis spp. in its number of chromosomes and its morphology...
grapes have a natural resistance. Pierce's disease is presently found in the southeastern United States, Mexico, Costa Rica, and Venezuela, and possibly in other parts of Central and South America. There are isolated hot spots of the disease near creeks in Napa and Sonoma in northern California.
Currently, work is underway at U.C. Davis to breed PD resistance into Vitis vinifera. The first generation was 50% high quality vinifera genes, the next 75%, the third 87% and the fourth 94%. In the spring of 2007, seedlings that are 94% vinifera were planted.
When a vine becomes infected, the bacterium causes a gel to form in the xylem
Xylem
Xylem is one of the two types of transport tissue in vascular plants. . The word xylem is derived from the Classical Greek word ξυλον , meaning "wood"; the best-known xylem tissue is wood, though it is found throughout the plant...
tissue of the vine, preventing water from being drawn through the vine. Leaves on vines with Pierce's disease will turn yellow and brown, and eventually drop off the vine. Shoots will also die. After one to five years, the vine itself will die. The proximity of vineyards to citrus orchards compounds the threat, because citrus is not only a host for the sharpshooter eggs, but it is also a popular overwintering site for the insect. Likewise, oleander
Oleander
Nerium oleander is an evergreen shrub or small tree in the dogbane family Apocynaceae, toxic in all its parts. It is the only species currently classified in the genus Nerium. It is most commonly known as oleander, from its superficial resemblance to the unrelated olive Olea, but has many other...
, a common landscaping plant in California, serves as a reservoir for Xylella.
Oleander leaf scorch
Oleander
Nerium oleander is an evergreen shrub or small tree in the dogbane family Apocynaceae, toxic in all its parts. It is the only species currently classified in the genus Nerium. It is most commonly known as oleander, from its superficial resemblance to the unrelated olive Olea, but has many other...
s (Oleander nerium) caused by a strain of X. fastidiosa which has become prevalent in California and Arizona, USA. The disease is transmitted by another sharpshooter (Homalodisca liturata), a leafhopper.
Genome sequencing
The genome sequencing of X. fastidiosa was realized by a pool of over 30 research labs in the State of São Paulo, Brazil, and funded by this State's Science Foundation (FAPESP).Links
- Public Intellectual Property Resource for Agriculture Pierce's Disease Website
- APHIS. 2002. Glassy-winged Sharpshooter and Pierce's Disease in California
- Univ. of Arizona. 2006 Oleander leaf scorch
Footnotes