Biocontrol Potential of Sclerotinia sclerotiorum and Physiological Changes in Soybean in Response to Butia archeri Palm Rhizobacteria

Sclerotinia sclerotiorum is a necrotrophic parasitic fungus that causes Sclerotinia stem rot (SSR), which is currently one of the most difficult agronomic crop diseases to control. A number of plants of the Brazilian Cerrado biome have been shown to be important sources of symbiotic microorganisms with biotechnological potential, so we decided to test the potential of bacteria isolated from the dwarf jelly palm, Butia archeri (Arecaceae) for the control of the pathogenic effects provoked by S. sclerotiorum. For this, we bioprimed seeds and evaluated the effects of this biopriming on the OJIP transient patterns prior to and following infection by the phytopathogen. Plants treated with the BA48R strain of Enterobacter sp., and in particular, those treated with the BA88R strain of Bacillus cereus presented the best results in terms of the loss/gain of the physiological and symptomatological variables evaluated. The plants bioprimed with BA88R presented high post-infection levels of total chlorophyll (33.35 FCIs) and chlorophyll a (26.39 FCIs), maintained a high Nitrogen Balance Index (NBI = 18.87), and synthesized low concentrations of flavonoids (1.39). These plants also maintained high levels of PI(ABS) (1.111) and PI(TOTAL) (1.300) following infection, and low levels of Di(0)/RC (0.602), which indicates that, in the presence S. sclerotiorum, the efficiency of the photosynthesis in the plants treated with these bacteria was less affected in the reaction centers, as confirmed by the negative amplitude recorded in the L band. The present study reconfirms the importance of the use of chlorophyll fluorescence for the diagnosis of disease and conditions of stress in crop plants, in addition to demonstrating the effectivenesss of the BA48R bacterial strain and, in particular, the BA88R strain on systemic resistance induction and suppression of S. sclerotiorum in Glycine max plants, with enormous potential for the development of more sustainable agricultural processes.