Novel Effects of Leonardite-Based Applications on Sugar Beet

Abstract

The present study aimed to explore the effects of foliar application of a leonardite-based product on sugar beet (<i>Beta vulgaris</i> L.) plants grown in the field. The approach concerned the evaluation of the community compositional structure of plant endophytic bacteria through a metabarcoding approach, the expression level of a gene panel related to hormonal metabolism and signaling, and the main sugar beet productivity traits. Results indicated that plants treated with leonardite (dosage of 2,000 ml ha^-1, dilution 1:125, 4 mg C l^-1) compared with untreated ones had a significant increase (<i>p</i> < 0.05) in (i) the abundance of <i>Oxalicibacterium</i> spp., recognized to be an endophyte bacterial genus with plant growth-promoting activity; (ii) the expression level of <i>LAX2</i> gene, coding for auxin transport proteins; and (iii) sugar yield. This study represents a step forward to advance our understanding of the changes induced by leonardite-based biostimulant in sugar beet.