The overexpression of antifungal genes enhances resistance to rhizoctonia solani in transgenic potato plants without affecting arbuscular mycorrhizal symbiosis

FERNANDEZ BIDONDO, L.; ALMASIA, N.; BAZZINI, A.; COLOMBO, R.; HOPP, E.; VAZQUEZ-ROVERE, C.; GODEAS, A.

CROP PROTECTION

ELSEVIER SCI LTD

Año: 2019 vol. 124

0261-2194

Abstract: Biological control of fungal diseases by using geneticallymodified (GM) plants could decrease the input of chemical pesticides.With the aim of avoiding losses in potato (Solanum tuberosum) yield, themost important tuber crop worldwide, due to the plant susceptibility tosoil fungal pathogens, the production of potato transgenic lines whichexpress genes encoding antifungal proteins has been conducted. However,all GM crops must be monitored in their potentially detrimental effectson non-target soil microorganisms. Arbuscular mycorrhizal (AM) fungi aregood candidates for this type of analysis, as they are good indicators ofa normal rhizosphere structure and functionality.In this work, potato lines, with over-expression of genes encodingpeptides with antifungal properties, have been monitored on their effectson the soil-borne fungal pathogen Rhizoctonia solani and on AM fungi.Six GM potato lines (AG-1, AG-3, RC-1, RC-5, AGRC-8 and AGRC-12) werechallenged against a highly virulent strain of R. solani, showing higherreduction in infection indexes when compared to untransformed plants. InRC-1, RC-5 and AGRC-12 lines growth was almost not affected by thepathogen, showing the maximum inhibition of R. solani infection. Level ofroots colonization by the AM fungus Rizophagus intraradices (pure invitro isolated) did not significantly differ between transgenic lines andwild potato lines under in vitro and microcosm conditions. An increase inmycorrhization was observed with the addition of potato biomass residuesof these GM lines when compared to residues of wild type potato line. Inaddition to R. intraradices assays, soil samples from sites with atleast100 year history of potato crop were collected as source of inoculumfor microcosm assays with potato lines. A significantly higher level ofnative mycorrhization and arbuscules development in roots of AGRC-12 GMline was detected. In general, potato lines seem to be less receptive ofR. intraradices pure inoculum than of AM species from the natural inoculum. In this work, non-adverse effect of selected GM potato lines onthe colonization by AM fungi was observed.