Phytoplasma diseases and climate change.

Phytoplasma associated diseases are long time know world wide as inducing severely economic damages on a variety of cultivated and wild plants. These uncultured parasites are bacteria lacking the cell wall and with transkingdom habitats such as phloem of infected plants and hemolymph of insect vectors. Their genomes are among the smallest of self replicating living organisms due to the drastic genome reduction achieved trough a degenerative evolution. The increasing threat of phytoplasma diseases worldwide comes both from emerging diseases in Africa, Latin America and the Caribbean mainly in sugarcane, corn, coconuts, papaya, and vegetables and from devastating epidemics in the rest of the world in grapevines, citrus, forest trees, oil-seed crops, alfalfa, stone and pome fruits. In both cases disease have the potential to spread to other crop species throughout the world and/or impact of global trade. There are concerns that climate changes resulting from global warming may facilitate the spread of these phytoplasma diseases to new areas and to additional crops, particularly if the vectors become more widespread and able to survive during warmer winters. Phytoplasmas usually do not kill in short time the host plant from which they are strongly metabolic dependent, however unusually cold conditions kill infected plants, while under tropical conditions asymptomatic plant presence is frequent with severe epidemiological consequences. Moreover phytoplasma-infected plants result more susceptible or to infection by other pathogens such as Venturia inequalis, Spiroplasma kunkelii, Acholeplasma palmae, and very often diverse viruses. Considering the high phytoplasma ability to adapt and colonize new ecological niches, financial losses for world economies can be foreseen if measures are not taken towards an efficient management of these diseases