Tolerance increase to pear decline phytoplasma in mycorrhizal OHF-333 pear rootstock

The cultivated Pyrus communis OHF-333 rootstock is known to be moderately susceptible to Pear decline (PD) phytoplasma. The interaction between the arbuscular mycorrhizal fungus (AM) Glomus intraradices, obtained from in vitro culture, and PD phytoplasma was studied on this rootstock. During the first year, while PD-infected trees were negatively affected by the disease, the inoculation with G. intraradices significantly increased shoot length both in non-PD and PD infected pear trees. Second-year results confirmed the beneficial long-term effect of mycorrhizae. Although PD infection was detrimental to plant shoot growth no effects in plant stem diameter were found. The effect of the G. intraradices symbiosis in PD infected pear trees is discussed.