Evidence for increased tolerance to phytoplasma disease in arbuscular mycorrhizal tomato plants
G. Berta1, G. Lingua1, N. Massa1, M. Antosiano1 and G. D'Agostino2
1DiSTA, Università del Piemonte Orientale "A. Avogadro", Alessandria - ITALY
2IFA, CNR Torino - ITALY
Phytoplasmas are prokaryotes responsible for severe diseases in wild and cultivated plants. Analyses, particularly of roots, by morphometry, light and electron microscopy, and flow cytometry showed that tomato (Lycopersicon esculentum) plants infected with the phytoplasmas (Phy) of the Stolbur group showed milder symptoms when they were colonized by the arbuscular mycorrhizal (AM) fungus Glomus mosseae. In AM plants, the phytoplasmas were often degenerated and morphometric parameters differed significantly from those of Phy plants, and were nearer to those of the uninfected controls. At each ploidy level, Phy caused a reduction of the DNA content, but in AM+Phy plants the results were identical to the controls and significantly higher than those of Phy plants. In AM+Phy plants the percentage of diploid nuclei, whose increase is a marker of pathogen-induced stress, was also intermediate between those of AM and Phy plants, although the difference was no significant.
