EFFECT OF TREATMENTS TO ELIMINATE SYSTEMIC PATHOGENS FROM SUGARCANE SETTS

摘要

Treatments were evaluated for the elimination of systemic pathogens of sugarcane from one-budded setts. Two sugarcane varieties were used, CC84-75 infected with Xanthomonas albilineans, the causal agent of leaf scald, and B69-613 infected with both Leifsonia xyli subsp. xyli, the causal agent of ratoon stunting disease (RSD), and Sugarcane yellow leaf virus (SCYLV), the causal agent of yellow leaf. The following treatments were evaluated alone and in various combinations: hot water treatment (HWT; 3 h/50℃ for X. albilineam, and 30 min/52℃ for L. xyli subsp xyli and SCYLV), plantlet thermotherapy (PT, 3 weeks at 41℃ after planting into trays) and meristem tissue culture (MTC), together with an untreated control treatment. The final incidence of the pathogens after eight months of growth in the field was determined on a percentage of infected stalks basis by dot blot immunoassay for X. albilineam and L. xyli subsp. xyli and by tissue blot immunoassay for SCYLV. The combination of H WT, PT and MTC resulted in the lowest incidence of X. albilineans (2% final incidence) and the other treatments gave similar degrees of control, compared with 80% for the untreated plants. Similarly, the combined use of HWT, PT and MTC resulted in the lowest incidence of SCYLV, 19%, compared with 78% for the untreated plants. For L. xyli subsp. xyli, all treatments eliminated the causal agent completely, whereas there was a 97% incidence in the untreated plants. The mean effect of treatments to control RSD and SCYLV in variety B69-613 was to increase cane yield by 27%. There was some evidence of a depressing effect of SCYLV on sugarcane yield.