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Poster: Molecular & Cellular Plant-Microbe Interactions: Biochemistry & Cell Biology


Stalk sugar content and charcoal rot disease reaction in grain sorghum
A. BANDARA (1), D. Weerasooriya (1), S. Liu (1), C. Little (1) (1) Kansas State University, U.S.A.

Charcoal rot, caused by Macrophomina phaseolina (MP), is an important fungal disease in grain sorghum (Sorghum bicolor (L.) Moench). An RNA-Seq experiment was conducted to explore the molecular basis of the sorghum-MP interaction. Stalk RNA extracted from MP- and mock-inoculated resistant (SC599) and susceptible (Tx7000) sorghum lines at 2, 7, and 30 d post-inoculation (d.p.i.) was subjected to RNA-Seq. Genes involved in UDP-glucose conversion, sucrose degradation to ethanol and lactate, and fructose degradation to pyruvate and lactate metabolism were significantly up-regulated in Tx7000 at 7 d.p.i., while those of SC599 were not differentially expressed. To confirm the results, stalk juice was extracted at 7 d.p.i from two MP- and mock-inoculated resistant (SC599, SC35) and susceptible (Tx7000, BTx3042) lines and subjected to HPLC. Concentrations (mg/mL) of sucrose, glucose, and fructose in stalk juice of SC599 (95.3, 23.9, 20.7, respectively) and SC35 (66.2, 31.2, 23.4) were significantly greater than those of Tx7000 (2.7, 6.5, 4.1) and BTx3042 (9.1, 10.9, 6.9) across MP- and mock-inoculations (P < 0.0001). Moreover, the reduction of sucrose, glucose, and fructose in MP-inoculated susceptible lines was 86.4, 26.5, and 19.8%, respectively, while those of the resistant lines were 17.0, 21.5, and 7.3%. Therefore, sorghum genotypes with higher stalk sugar content along with lesser sugar reduction under MP infection appeared to be more resistant to charcoal rot disease