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Poster: Diseases of Plants: Crop Loss Assessment


Impact of stalk rot diseases on sweet sorghum sugar concentration and content.
A. BANDARA (1), T. Tesso (1), D. Wang (1), K. Zhang (1), C. Little (1) (1) Kansas State University, U.S.A.

The sugar-rich nature of sweet sorghum [Sorghum bicolor (L.) Moench] makes it an attractive bioethanol feedstock. Fusarium stalk rot (Fusarium thapsinum, FT) and charcoal rot (Macrophomina phaseolina, MP) are high priority fungal diseases of sorghum, which can potentially affect sweet sorghum biofuel traits. The objective of this study was to test the effects of FT and MP on sweet sorghum sugar concentration and content. Seven parental lines and 12 hybrids were field evaluated in 2014 and 2015. At 14 d after flowering, plants were inoculated with FT, MP, and phosphate-buffered saline (control). Plants were harvested at 35 d after inoculation and measured for disease severity using stem lesion length. Juice volume (per plant) extracted from stalks was measured and subjected to HPLC to determine sugar concentration (mg/mL). ANOVA revealed non-significant pathogen main or simple effects on glucose and fructose concentration and significant genotype × pathogen effect on sucrose concentration. Pathogens did not significantly affect the total sugar concentration (= ∑ sucrose, glucose, fructose). However, when analyzed for content (g/plant), genotype × pathogen and environment × pathogen effects were evident for total sugars and sucrose. Pathogens affected glucose and fructose content in an environment-specific manner. Therefore, in general, stalk rot pathogens do not affect the concentration of major sweet sorghum sugars, but do affect sugar content.