The Variations among Isolates of Sugarcane Mosaic Virus in Thailand as Determined by Virus-Host Interaction

Abstract

Six isolates of sugarcane mosaic virus (SCMV) were collected from infected sugarcane and their variations were studied using symptom expression in sugarcane, corn and sorghum cultivars. Virus titer of each isolate in sorghum plant was also compared. Mechanical inoculation was applied for virus infection and ELISA was used for virus titer assay. The incubation period for symptom expression of SCMV in sugarcane, corn and sorghum was 4-15 days depending on host cultivars. Virus infection rates varied from 15-92% in sorghum,17-90% in corn, and 0-88% in sugarcane. On sugarcane, symptoms mostly appeared to be chlorotic or necrotic streak, chlorotic mild mottle or mild mosaic. The UT-3 and Q-67 sugarcane were the most susceptible cultivars to SCMV isolates as evaluated by infection rate. On sorghum, three types of expressed symptom were observed as lethal necrosis, chlorotic spot, and severe mosaic associated with streak or stripe pattern. On corn, symptoms were generally whitish mosaic or
streak, mottle, except for leaf chlorosis on DK888 or CP888 commercial hybrid corn. Isolates UD7 from Udon Thani and SP9 from Supan Buri were the most aggressive isolates based on the infection rate. Isolates NP5 from Nakhon Pathom and UT6 from U-Thong were likely to be the same while NS1 from Nakhon Sawan and KB2 from Kanchanaburi were different from the others. Virus titer in individual sorghum species varied upon SCMV isolates. High titer of virus was detected in UT-1 sorghum at 10-15 days post inoculation for all isolates tested. Necrosis and severe chlorosis were observed with high virus titer for isolates NS1, UD7 and NP5. The obtained results demonstrated the variations among SCMV
isolates in Thailand and this information could be used in breeding program for SCMV resistance.