Effects of silicon on resistance to bacterial fruit blotch and growth of melon

• Silicon supplied to soil elevated the resistance to bacterial fruit blotch in melon plants.
• Silicon application strongly modified the chemical soil attributes.
• Silicon did not affect Acidovorax citrulli directly.
• Silicon played an important role in melon nutrition, alleviating disease symptoms.

Melon bacterial fruit blotch (BFB) caused by Acidovorax citrulli is responsible for substantial yield losses in Northeastern Brazil, and management options for this disease are limited. Since silicon has been shown to suppress a number of plant diseases including some caused by bacteria, a study was conducted to determine if this element might reduce BFB development. Yellow melon hybrid AF 4945 plants were grown in plastic pots containing soil supplemented with calcium silicate (0.00, 0.12, 0.24, 0.71 and 1.41 g Si kg−1 of soil) and inoculated with A. citrulli 20 days after plant emergence. Incidence (INC) and severity were evaluated every 4 days up to 20 days after inoculation. In addition, the incubation period (IP), disease index (DI), and area under the disease progress curve (AUDPC) were determined. Plant growth along with macro- and micro-nutrient accumulation also were determined from 45-day-old plants. The highest Si dose significantly reduced INC (50%), DI (89%), and AUDPC (85%) and increased the IP (192%) in comparison to the control. This dose also elevated soil Si levels, soil pH and Ca + Mg respectively by 62, 17 and 29%, whereas H + Al was reduced by 62%. Plant height (9%), shoot (24%) and root (49%) fresh weights as well as shoot dry weights (33%) were also significantly increased by 1.41 g Si kg−1 of soil. At this dose, Ca and Mg shoot concentrations reached 124 and 59%, respectively, and Si content increased up to the 0.24 g Si (39%) in comparison to the control. Supplying Si to melon plants clearly enhanced resistance to BFB but also elevated Ca and Mg levels in the plant tissue. Improved plant nutrition in melon appears to play an important role in helping to suppress BFB development.