Silicon and Fungicide Effects on Anthracnose in Moderately Resistant and Susceptible Sorghum Lines.

This study aimed to evaluate the effect of silicon ( Si) and its interaction with fungicide on the management of sorghum anthracnose. The experiments were carried out in Si-deficient soil in the 2008/2009 and 2009/2010 growing seasons in a randomized, complete block, split-split plot design with four replications. Calcium silicate ( CS) and lime ( L), at the rates of 6 and 5 ton/ha, respectively, were randomly assigned to the main plot. Two sorghum lines, BR-008 (resistant) and BR-009 (susceptible), were assigned to the split plots. The split-split plots corresponded to with or without the fungicide Opera® (epoxiconazole + pyraclostrobin). The residual effect of CS and L from the 2008/2009 growing season was evaluated in the 2009/2010 growing season. For the 2008/2009 growing season, the area under anthracnose progress curve ( AUAPC) was reduced by 39 and 42% for lines BR-008 and BR-009, respectively, with the application of CS. In the presence of the fungicide, the AUAPC was reduced by 35 and 42% for the CS and L treatments, respectively. Calcium silicate with and without fungicide contributed to decreasing the AUAPC by 44 and 37%, respectively. The fungicide spray decreased the AUAPC by 50 and 39% for lines BR-008 and BR-009, respectively. Without fungicide, the AUAPC decreased by 88% for line BR-008 compared with line BR-009; however, with fungicide, the reduction reached 90%. The Si leaf tissue concentration significantly increased with the CS application (5.9 g/kg) compared with the L application (0.3 g/kg), regardless of the sorghum line. The yield increased by 0.6 ton/ha with the CS compared to the L application. The fungicide increased yield by 0.48 ton/ha compared with the non-fungicide spray treatment. The residual effect of CS in the soil increased Si leaf tissue concentration and yield as well as reduced the intensity of anthracnose in the 2009/2010 growing season. [ABSTRACT FROM AUTHOR]