Submitted to: International Society of Sugar Cane Technologists Pathology Workshop
Publication Type: Abstract Only
Publication Acceptance Date: 3/26/2004
Publication Date: 4/1/2004
Citation: Comstock, J.C., Miller, J.D. 2004. Reliability of leaf-midrib tissue blot immunoussay to detect sugarcane yellow leaf virus and differences between cultivars in rate of spread. International Society of Sugar Cane Technologists Pathology Workshop. J. Amer. Society Sugar Cane Technologists 24:41-40. Interpretive Summary: The presence of sugarcane yellow leaf virus in sugarcane plants was determined using a leaf-midrib tissue blot that was able to sample large number of plants quickly. For three of five sugarcane cultivars sampled the results were consistent with less than 3 % false negatives while the other cultivars had 8.5 and 25 % false negatives. False positives were 5 % or less for all five cultivars. Multiple samples from the same plant may be required for some cultivars. The natural infection of plants differed among cultivars indicating a possible type of resistance and a factor that may influence the use of virus-free plants to control the disease.
Technical Abstract: The reliability of the leaf-midrib tissue blot immunoassay in detecting sugarcane yellow leaf virus (SCYLV) and the rate of spread of the virus was evaluated using five CP-cultivars. Stalks were cut from healthy and infected plants of each cultivar and were planted in a split plot design with forty blocks in March 2001. The disease state of each plot was determined in May, October and December of 2001 and in April, July and September of 2002 using the leaf-midrib tissue blot immunoassay technique. Three top visible dewlap leaf samples per plot were taken in May and October of 2001 with one sample taken the other four times for a total of 10 assays per plot. False negatives were defined as a negative assay in plants that assayed positive for four or more collection times. Interestingly, CP 89-2143 had a high number of false negatives (25 %) while the other cultivars had considerable fewer: CP 72-1210 (1.9 %), CP 80-1827 (1.7 %), CP 84-1198 (2.5 %), and CP 85-1382 (8.5 %). False positives were defined as a positive assay from a plant in 2001 that assayed negative in all assays of 2002. The percent false positive assays were: CP 72-1210 (5.7 %), CP 80-1827 (3.1 %), CP 84-1198 (2.5 %), CP 85-1382 (5.3 %) and CP 89-2143 (1.9 %). During the test, a number of healthy plots became infected with SCYLV and the infection rate differed among the cultivars. In December 2001, the percent SCYLV infected plants was 64.9 % for CP 72-1210, 25.6 % for CP 80-1827, 22.2 % for CP 84-1198, 12.5 % for CP 85-1382 and 19.5 % for CP 89-2143. The level of infection continued to increase during 2002. The results indicate that the leaf-midrib tissue blot immunoassay is effective in detecting the virus in most cultivars but either due to a low virus titer and/or non-uniform distribution of the virus in plants of CP 89-2143 there was a high number of false negative assays. Multiple samples of plants of this cultivar are required. The variable rate of disease spread between cultivars may reflect a type of resistance and will influence the effectiveness of using disease-free seedcane to control the disease.