Poster Session: Diseases of Plants - Disease Detection and Diagnosis

407-P

Incidence and impact of dual infection by Panicum mosaic virus and its satellite virus in switchgrass breeding fields.
C. L. Stewart (1), C. Jochum (1), G. Y. YUEN (1), K. Vogel (2), J. D. Pyle (3), K. B. G. Scholthof (3)
(1) University of Nebraska, Lincoln, NE, U.S.A.; (2) USDA-ARS (retired), Lincoln, NE, U.S.A.; (3) Texas A&M University, College Station, TX, U.S.A.

Panicum mosaic virus (PMV) and satellite panicum mosaic virus (SPMV) were detected in field-grown switchgrass (Panicum virgatum) in Nebraska in 2012. Mixed infection by PMV+SPMV in other grasses heightens symptom expression over PMV alone. This study aimed to assess PMV- or PMV+SPMV-infection incidence and associated symptoms in biofuel switchgrass breeding fields in Nebraska. PMV and SPMV were detected by ELISA and RT-PCR, respectively, in leaf samples from randomly selected plants. Symptom severity was assessed on these plants using a 1 to 5 scale (1 = no symptoms; 5 = plants stunted and >50% foliage with mottling). PMV-infection incidence varied widely among fields and switchgrass populations within fields, e.g. 11% and 77% PMV infection occurred in ‘Kanlow’ and ‘Summer’, respectively, in one field. Common among sampled populations was dual infection by PMV and its satellite virus. Plants infected with PMV alone exhibited none to moderately severe symptoms (1 to 3 rating). There also were many PMV+SPMV-infected plants that exhibited none to mild symptoms, although other plants infected with both viruses displayed severe symptoms (ratings of 4 or 5). These results suggest that while SPMV might enhance PMV transmission and establishment in switchgrass, it heightens symptom expression in a host-dependent manner. Furthermore, resistance to PMV within current switchgrass populations may be useful in developing more productive biofuel cultivars.