engleski

Flavescence Dorée Phytoplasma Heavily Affects Photosynthetic Pigment Content In Grapevine (Vitis vinifera) var. ‘Pinot Gris’ Leaves

The flavescence dorée phytoplasma (ribosomal group 16SrV) is one of the causative agents of grapevine yellows disease. This bacterial disease is spread by the vector, leafhopper Scaphoideus titanus in european vineyards. It causes heavy damage to plants and severely influences productivity, which heavily affects viticultural production. However, at this moment, there is no way of stopping the spread of the disease apart from removing infected plants from the affected vineyards and by using insecticides to manage the spreading of the vector. In order to investigate the pathogenic mechanisms of the flavescence dorée phytoplasma in grapevine, we evaluated whether the infection influences the content of photosynthetic pigments in infected grapevine leaves in comparison to the leaves of uninfected plants. Therefore, we sampled the leaves of symptomatic and asymptomatic plants to evaluate the dynamics of photosynthetic pigment content. Using real-time PCR, we confirmed the infection with the flavescence dorée phytoplasma in symptomatic plants. Additionally, by amplification, sequencing and phylogenetic analysis of map gene amplicons, we detected two distinct flavescence dorée phytoplasma genotypes in sampled grapevine leaves, M38 and M54, both belonging to the mapFD1 cluster. Therefore, we also analysed if the effect of the flavescence dorée phytoplasma on photosynthetic pigment content in grapevine is dependant on phytoplasma genotype. The extraction of photosynthetic pigments was performed using acetone as a solvent and the photosynthetic pigment content was measured spectrophotometrically. Results revealed the lower concentration off all photosynthetic pigments in infected plants compared to the uninfected plants. Considering that the leaf yellowing, which points to degradation of chlorophylls and other photosynthetic pigments, is the symptom of the flavescence dorée phytoplasma infection in grapevine, the drop in photosynthetic pigment content in infected plants is not surprising. Furthermore, a reduction of the chlorophyll a/b ratio was also observed in infected leaves compared to the leaves of uninfected plants. Along with chlorophylls, severe reduction was also observed for total carotenoid content, as well as the content of individual carotenoids, β-carotene and lycopene in infected leaves compared to the leaves of uninfected plants. Also, it was revealed that different phytoplasma genotypes affect the concentration of photosynthetic pigments with different severity. All results point to the degradation of photosynthetic pigments in grapevine upon infection with the flavescence dorée phytoplasma. Consequentally, this could have great effect on photosynthetic performance of grapevine leaves and cause severely lower yield. The future studies should reveal the mechanisms of interaction between the flavescence dorée phytoplasma and photosynthetic apparatus of grapevine leaves and ways to alleviate these effects in order to prevent huge losses to viticultural production.

grapevine ; photosynthesis ; phytoplasmas ; plant-pathogen interactions

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