Impact of Anthracnose Infection on Biomass Composition and Yield of Switchgrass Cultivars.

Anthracnose, caused by Colletotrichum navitas, may negatively impact the cultivation of switchgrass (Panicum virgatum L.) in the United States for cellulosic ethanol production.  As a destructive plant pathogen, anthracnose may reduce both the quantity and quality of biomass on a yearly basis.  Research is necessary, however, to fully understand the direct influence anthracnose will have on switchgrass growth and development.  Therefore, the objectives of this study were to (i) quantify yield reductions attributed to anthracnose infection among switchgrass cultivars and (ii) determine the influence of anthracnose on quality of switchgrass biomass.  Seeded plots (5.5 x 1.8 m) were established with 16 switchgrass cultivars in 2013 at the Rutgers Plant Biology and Pathology Research and Extension Farm in Freehold, NJ.  Treatments consisted of spraying half of each plot (2.75 m) with a combination of azoxystrobin and acibenzolar-S-methyl in order to control anthracnose disease on half of the plot.  Measurements included visually rating anthracnose infection (1-10 scale, 1 = 100% anthracnose and 10 = 0% or no anthracnose), biomass yield determination at the end of the growing season, and analyzing leaf and stem samples for lignocellulosic composition.  A negative correlation was detected between biomass yield and anthracnose infection.  In addition, differences in anthracnose resistance were observed and varied by cultivar. ‘Forestburg’ was most susceptible to anthracnose and had the lowest biomass yield compared to all other cultivars in the study.  In addition, biomass composition differenced among the cultivars evaluated; however, the variability was not correlated with anthracnose infection.  Overall, this research indicates that fungicides may reduce anthracnose severity of susceptible cultivars but has little effect on cultivars exhibiting increased resistance to infection.  Therefore, selecting and breeding cultivars with improved resistance to anthracnose infection looks promising to maintaining high yields and reducing environmental impacts.