Distribution and incidence of sugarcane mosaic in Louisiana and evaluation of recovery from infection
Jancee Rice: Louisiana State University
<div>In Louisiana, sugarcane mosaic is currently caused by Sorghum mosaic virus (SrMV). Development of resistant cultivars has resulted in low mosaic incidence. Recently, resistance selection has relied on distinguishing susceptibility/resistance based on natural infections. With decreased infection pressure, susceptibility may escape detection, and mosaic was detected in advanced selections and a new cultivar HoCP 09-804. To prevent mosaic from re-emerging as an important problem, multiple lines of research were undertaken. Field surveys were conducted in 2016 and 2017 in breeding program yield trials and cultivar increase plots to determine disease incidence and distribution. Mosaic was detected in two of three areas, and incidence in HoCP 09-804 fields ranged from 0% to 10%. Runs analysis detected aggregation of infected plants in surveyed fields suggesting the source of infection was infected seed cane. Increases in incidence during 2017 ranged from -62 to +97%, and incidence ranged from 0.2 to 9.4%. "Recovery" evaluated as the production of asymptomatic plants from buds on symptomatic stalks was compared for two cultivars by planting single symptomatic and asymptomatic stalks. L 10-147 had a 19% frequency of asymptomatic plants growing from symptomatic stalks compared to 2% for HoCP 09-804. When apparently recovered plants were assayed by reverse transcription polymerase chain reaction, 67% of HoCP 09-804 and 95% of L 10-147 samples tested negative for SrMV.</div>
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