Interactive physiological response of potato (Solanum tuberosum L.) plants to fungal colonization and Potato virus Y (PVY) infection

Abstract

Potato plants can be colonized by various viruses and by symbiotic, saprophytic and pathogenic fungi. However, the significance of interactions of viral infection and fungal colonization is hardly known. This work presents a model experiment in which the influence of three different types of fungal associations on the growth and physiology of the potato variety Pirol was tested individually or in combination with infection by PVY. It was hypothesized that simultaneous viral and fungal infections increase the biotic stress of the host plant, but mutualistic plant-fungal associations can mask the impact of viral infection. In the present study, a symbiotic arbsucular mycorrhizal fungus, Glomus intraradices, significantly stimulated the growth of plants infected with PVY. In contrast, two saprophytic Trichoderma spp. strains either did not influence or even inhibited the growth of PVY-infected plants. Also, inoculation of PVY-infected potato plants with a pathogenic strain of Colletotrichum coccodes did not inhibit the plant growth. Growth of the PVY-free potato plants was not promoted by the symbiotic fungus, whereas T. viride, T. harzianum and C. coccodes had an evident inhibitory effect. The strongest growth inhibition and highest concentration of H 2 O 2 , as an indicator of biotic stress, was observed in PVY-free potato plants inoculated with T. harzianum and C. coccodes strains. Surprisingly, ultrastructural analysis of PVY-infected plant roots colonized by G. intraradices showed virus-like structures in the arbuscules. This pointed to the possibility of mycorrhizal-mediated transmission of virus particles and has to be further

Arbuscular Mycorrhiza Changes the Impact of Potato Virus Y on Growth and Stress Tolerance of Solanum tuberosum L. in vitro

“…ROS acting as long distance signal molecules play an important role during plant adaptation to biotic stress (Sewelam et al, 2016). Interestingly, our study revealed prolonged maintenance of elevated H 2 O 2 in mycorrhizal potato plantlets, which is in line with the previously described results (Thiem et al, 2014), however the basis of this observation is unclear and requires further consideration. Nevertheless, Hause and Fester (2005) demonstrated that H 2 O 2 is produced in arbuscules and the use of ROS scavengers (e.g., ascorbic acid and salicylhydroxamic acid) reduces both H 2 O 2 level and mycorrhizal development (Kapoor and Singh, 2017).…”

“…We noticed that healthy plantlets colonized with R. irregularis displayed growth parameters similar to the control, with the only significant differences found in the higher root biomass (but not length) and higher chlorophyll content upon mycorrhization. Beneficial effect of AMF on root biomass production was already described for potato (Davies et al, 2005;Thiem et al, 2014) as well as for the other plant species (Saia et al, 2015;Chen M. et al, 2017;Jacott et al, 2017;Shao et al, 2018). We cannot exclude that enhanced biomass (but not the length) of root system could be associated with some structural changes that are known to be induced by AMF (e.g., enlargement of root cortex due to an extra cell layer development for accommodation of fungal structures) (Dreyer et al, 2014).…”

“…H 2 O 2 may play a pivotal roles in pathogen control comprising (i) induction of the oxidative burst in hypersensitive response (HR) in order to inhibit pathogen infection development and (ii) activation of biotic stress response mechanism, e.g., SAR (systemic acquired resistance) pathway (Gilroy et al, 2016;Hernández et al, 2016). On the other side, constantly maintained high concentration of endogenous H 2 O 2 may exert toxic effect on plant development and contribute to the biomass reduction (Gapper and Dolan, 2006), which is suggested in this and previous studies (Thiem et al, 2014).…”

“…Additionally, comparison of H 2 O 2 concentration in plantlet shoot and root, showed that the second one was more severely impacted by the virus. Previously, Thiem et al (2014), using the same potato cv. Pirol grown in pots, found the long-term increase in amount of endogenous H 2 O 2 to be associated with PVY presence.…”

The Contribution of Endomycorrhiza to the Performance of Potato Virus Y-Infected Solanaceous Plants: Disease Alleviation or Exacerbation?

“…Significant attenuation of virus-induced plant disease following mycorrhizal establishment was shown in two research papers (Maffei et al., 2014; Thiem et al., 2014). Maffei et al.…”