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Title: A POTENTIAL NEW STRAIN OF SORGHUM MOSAIC VIRUS IN LOUISIANA

Author
item Grisham, Michael
item Pan, Yong-Bao
item Dufrene, Edwis

Submitted to: American Society of Sugar Cane Technologists
Publication Type: Abstract Only
Publication Acceptance Date: 5/20/2003
Publication Date: 6/20/2003
Citation: Grisham, M.P., Pan, Y., Dufrene Jr, E.O. 2003. A potential new strain of sorghum mosaic virus in Louisiana [abstract]. Sugar Journal. 66(1):33.

Interpretive Summary:

Technical Abstract: Ten strains of sugarcane mosaic virus (SCMV) and three strains of sorghum mosaic virus (SrMV) have been shown to cause sugarcane mosaic in Louisiana; however, surveys conducted between the 1970s and 1995 identified strains of SrMV only. In 2002, plants of an advanced breeding cultivar, HoCP 98-743, from an off-station test nursery were found to have severe symptoms of mosaic. The results of reverse transcriptase-polymerase chain reaction (RT-PCR) designed to distinguish between SCMV and SrMV indicated that a SrMV isolate was associated with the diseased cultivar. A restriction fragment length polymorphism (RFLP) analysis of the RT-PCR product was performed in an attempt to identify the strain of the virus isolate. The RFLP banding pattern, however, did not match any known strain of SrMV. The virus isolate was successfully transmitted by mechanical inoculation to `Rio¿ sweet sorghum on which severe mosaic symptoms developed. Healthy plants of HoCP 98-743, LCP 85-384 and CP 70-321 (the two most widely planted cultivars Louisiana), HoCP 96-540 (released in 2003), and six former commercial Louisiana cultivars including three historic cultivars known to be susceptible to SCMV and SrMV were mechanically inoculated with the infected juice from diseased sweet sorghum leaves. Fortunately, no inoculated plant of LCP 85-384 or HoCP 96-540 developed symptoms, and only one of 12 plants of CP 70-321 became infected. Approximately 10% of the plants of HoCP 98-743 and two former commercial cultivars, CP 72-370 and CP 79-318, became infected, while no plant of former cultivar, LHo 83-153, developed symptoms. The older historic cultivars known to be susceptible to SCMV and SrMV appeared to be the most highly susceptible among the cultivars tested with over 60 percent of plants becoming infected. The pathogenicity tests conducted with the virus isolate from HoCP 98-743 does not indicate that the new strain is an immediate threat to the leading cultivars of sugarcane in Louisiana. However, the discovery of an isolate with different molecular and pathological characteristics emphasizes the potential for new strains of the mosaic-causing viruses to develop, and in an industry such as Louisiana that is dependent on a single cultivar, LCP 85-384, for 85% of its production, a new strain of virus can pose a serious threat. Monitoring of virus strain development will continue.