Table_1_A biotroph sets the stage for a necrotroph to play: ‘Candidatus Phytoplasma solani’ infection of sugar beet facilitated Macrophomina phaseolina root rot.DOCX

‘Candidatus Phytoplasma solani’ (stolbur phytoplasma) is associated with rubbery taproot disease (RTD) of sugar beet (Beta vulgaris L.), while Macrophomina phaseolina is considered the most important root rot pathogen of this plant in Serbia. The high prevalence of M. phaseolina root rot reported on sugar beet in Serbia, unmatched elsewhere in the world, coupled with the notorious tendency of RTD-affected sugar beet to rot, has prompted research into the relationship between the two diseases. This study investigates the correlation between the occurrence of sugar beet RTD and the presence of root rot fungal pathogens in a semi-field ‘Ca. P. solani’ transmission experiment with the cixiid vector Reptalus quinquecostatus (Dufour), in addition to naturally infected sugar beet in the open field. Our results showed that: (i) Reptalus quinquecostatus transmitted ‘Ca. P. solani’ to sugar beet which induced typical RTD root symptoms; (ii) Macrophomina phaseolina root rot was exclusively present in ‘Ca. P. solani’-infected sugar beet in both the semi-field experiment and naturally infected sugar beet; and that (iii) even under environmental conditions favorable to the pathogen, M. phaseolina did not infect sugar beet, unless the plants had been previously infected with phytoplasma.</p

Soil chemical properties.

<p>Soil chemical properties.</p

CAT, APx, GPx and GST activities in the leaves (A) and roots (B) of sugar beets after exposure to drought stress.

<p>*dark bars–<i>Control</i>, light gray bars—<i>Drought 1</i>, gray bars—<i>Drought 2</i>. Enzymes activities are expressed in units of enzyme activity per milligram of protein. Different letters in the same chart indicate significant differences between treatments according to Fisher’s test (p < 0.05), representing the means of three independent measurements ± SD.</p

Proline content in sugar beet leaves.

<p>Different letters indicate significant differences between treatments according to Fisher’s test (p < 0.05), representing the means of three independent measurements ± SD.</p

Photosynthetic and transpiration rate of treated plants.

<p>Photosynthetic and transpiration rate of treated plants.</p

FNP particle size distribution measurements by DLS.

<p>DLS size distributions for FNPs at 2 concentrations and time points: 700 μmol/L FNP (black line-30 min, blue line-24h); 70 μmol/L FNP (red line-30 min, green line-24h).</p

TEM image of FNP solution.

<p>TEM image of FNP solution.</p

Fresh weight of leaves and roots and saccharose content in roots.

<p>Fresh weight of leaves and roots and saccharose content in roots.</p

Soil mechanical composition.

<p>Soil mechanical composition.</p

Malondialdehyde (MDA) and reduced glutathione (GSH) content in the leaves (A) and roots (B) of sugar beets after exposure to drought stress.

<p>*dark bars–<i>Control</i>, light gray bars—<i>Drought 1</i>, gray bars—<i>Drought 2</i>. MDA and GSH contents are expressed per milligram of protein. Different letters in the same chart indicate significant differences between treatments according to Fisher’s test (p < 0.05), representing the means of three independent measurements ± SD.</p