Tests find trees tolerant to olive tree killer pathogen

Tests find trees tolerant to olive tree killer pathogen


Tests suggests some varieties of olive trees appear to be resistant to an invasive pathogen posing a serious risk to Europe’s olive industry.The findings came to light during a study into the host range of the bacteria, which reached Europe in 2013.The findings offer hope of limiting the impact of a disease that experts have described as one of the “most dangerous plant pathogens worldwide”.If it is not controlled, it could decimate the EU olive oil industry.The study, carried out by Italian researchers and funded by the European Food Safety Agency (EFSA), began in 2014 and consisted of two main types of experiment: artificial inoculation (via needle) and inoculation via infected vectors (insects) collected from the field.The tests were carried out on a variety of species, including a range of olive, grape, stone-fruit (almond and cherry) and oak varieties.”The first results are coming from the artificial inoculation because the field experiments began in the summer so it is only six months old, therefore only part of the results are available,” Giuseppe Stancanelli, head of the EFSA’s Plant and Animal Health Unit, told BBC News.”The key results are that, 12-14 months after artificial inoculation on different olive varieties, the team found that young plants typically grown in the region displayed symptoms of the dieback.”The research team also found evidence of the bacterium moving through the tree – towards it root system as well as towards the branches.”But he added: “What has also been shown is that some varieties have shown some tolerance.

They grow in infected orchards but do not show strong symptoms, as seen in more susceptible varieties.”They are still infected by the inoculation but this infection is much slower so it takes longer for the infection to spread, and the concentration of the bacterium in the plant is much lower.”This shows the potential for different responses (to the pathogen) in different varieties.”Dr Stancanelli added that these results were important in terms of providing information for tree breeders.However, it was too early to say whether or not the olive yields from the varieties that have displayed tolerance to the infection are nonetheless reduced or adversely affected, he observed.The EFSA Panel on Plant Health produced a report in January warning that the disease was known to affect other commercially important crops, including citrus, grapevines and stone-fruit.However, the results from the latest experiments offered a glimmer of hope.”Olives seemed to be the main host of this strain while citrus and grapes did not show infection, either in the field or by artificial inoculation,” Dr Stancanelli said.He added that the infection did not spread through the citrus and grape plants that were artificially inoculated, and the bacterium was not found beyond the point it was introduced to the plant by injection.But he added that more research was needed on stone-fruit species.”The tests on the artificially inoculated varieties of stone-fruit need to be repeated because there is a mechanism in the plants that makes artificial inoculation difficult,” Dr Stancanelli explained.”Another uncertainty we had was about (holm) oak. Quercus ilex is a typical Mediterranean oak that grows in the landscape and is natural vegetation.”At the beginning of the outbreak in 2014, some symptoms were found on oaks and the tests were positive but this was never confirmed so this was probably a ‘false positive’.”The artificial inoculation test appears to have shown that the holm oak is resistant (to the disease).”
source: BBC


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