Author
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Schaad, Norman |
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Submitted to: Kluwer Academic Press
Publication Type: Book / Chapter Publication Acceptance Date: 11/23/2007 Publication Date: 6/24/2008 Citation: Schaad, N.W. 2008. Emerging Plant Pathogenic Bacteria and Global Warming. In: Fatmi, M.B. editor. Pseudomonas syringae Pathovars and Related Pathogens. Dordrecht, The Netherlands: Springer Science + Business Media B.V. 369-379. Interpretive Summary: Several plant pathogenic bacteria, incuding Ralstonia, Acidovorax, and Burkholdria have emerged as serious problems world-wide. Perhaps the most destructive is R. solanacearum, a soilborne pathogen infects tomato, pepper and potato. A. Avenae, a pathogen of corn and rice has emerged as a disease of upland rice in Southern Europe during periods of high temperatures. B. glumae is emerging as a problem on rice in the southern United States and is more prevelant in southern South Korea during periods of high temperatures. Why the increase in these bacteria? One possible explanation is global warming. A common trait among them is an optimum growth temperature of 32 to 36 degrees C; most grow well up to 41 degrees C. Controlled temperature studies with A. avenae and corn have shown an increase in the night temperature from 22 to 26 degrees C resulted in 40 percent increase in disease. An increase in extreme weather conditions, including extended heat waves, long periods of rain, and storms such as hurricanes appear to favor these high-temperature bacteria. There has been a gradual increase in the mean global temperature over the past century. Recent summer temperatures in the southern US have been 1-2 degrees C higher than that which is optimum for many crops. Several heat waves have occurred in Europe and the U.S. in recent years. An increase in violent and extreme summer storms has increased the spread of bacterial pathogens. If such conditions continue, damage caused by these heat-loving bacteria should be expected to increase. Technical Abstract: Several bacteria, previously classified as non-fluorescent, oxidase positive pseudomonads, Ralstonia, Acidovorax, and Burkholdria have emerged as serious problems world-wide. Perhaps the most destructive is R. solanacearum (RS), a soilborne pathogen with a very wide host range. RS race 3, biovar 2 infects potato and geranium during cooler weather making it an additional threat. Acidovorax avenae subsp. avenae has emerged as a disease of upland rice in Southern Europe during periods of high temperatures and B. gladioli has emerged as a serious pathogen of orchids in Thailand. B. andropogonis has been identified for the first time on jojoba in eastern Australia; the plant grows under very high temperatures and the disease occurs in nursery stock grown under overhead watering. Burkholderia glumae is emerging as a problem on rice in the southern United States and the pathogen has become much more prevelant in southern South Korea during periods of high temperatures. Why the increase in these bacteria? One possible explanation is global warming. A common trait among them is an optimum growth temperature of 32 to 36 degrees C; most grow well up to 41 degrees C, whereas most other plant pathogenic bacteria grow best at lower temperatures. An increase in extreme weather conditions, including extended heat waves, long periods of rain, and storms such as hurricanes appear to favor these high-temperature bacteria. There has been a gradual increase in the mean global temperature over the past century. Recent summer temperatures in the southern US have been 1-2 degrees C higher than that which is optimum for many crops. Evidence is growing that the increase in the occurrence of extreme weather, including heat waves, continual rains, and hurricanes is caused by rising CO2 levels from expanding world economies. Several heat waves have occurred in Europe and the U.S. in recent years. The year 1995 was the warmest since global records began in 1856, and the 2003 heat wave killed hundreds in Europe. An increase in violent and extreme summer storms has occurred the past several years. Ice core studies, photographic recordings of retreating glaciers, and recorded temperatures provide solid evidence that global warming is occurring at an alarming rate. If such conditions continue, damage caused by these heat-loving bacteria should be expected to increase. |
