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Effect of Sugarcane Mosaic caused by Sorghum mosaic virus on Sugarcane in Louisiana

Michael Grisham: USDA-ARS, SRU

<div>To determine the effect of mosaic caused by the S<em>orghum mosaic virus </em>on sugarcane<em>, </em>experimental field plots were planted with seed cane with mosaic symptoms (mosaic plots) or without mosaic symptoms (control plots). Commercial (Ho 05-961 and HoCP 09-804) and advanced candidate (Ho 09-832, L 08-88, and L 09-117) sugarcane cultivars were included. The plant-cane (first-year crop) and three subsequent ratoon crops were harvested annually from 2013 through 2016. Cane and sugar yields were determined using total plot weights and laboratory determined theoretically recoverable sucrose (TRS). The average cane yield (Mg ha<sup>-1</sup>) was numerically lower among all mosaic plots in plant-cane compared to control plots. Average cane yields were reduced in mosaic plots across all crops for Ho 05-961, HoCP 09-804, and L 08-88, except in the first ratoon of HoCP 05-961. Because average TRS (kg Mg<sup>-1</sup>) was higher in many mosaic plots compared to control plots, sugar yields (kg ha<sup>-1</sup>) were not reduced in some crops where cane yields were reduced. Across all crops, mosaic reduced sugar yields in L08-88 and HoCP 09-804 by 21% and 7% as compared to the controls, respectively. Mosaic incidence (% shoots with symptoms) was determined each spring. Natural spread of mosaic was noted among control plots of all cultivars resulting in mosaic incidence increasing from crop to crop. In the third ratoon, mosaic incidence among control plots ranged from 16 to 47%.</div>