2012 Annual Report
1a.Objectives (from AD-416):
The objective of this study is to determine the likelihood of seed transmission of sugarcane pathogens with the ultimate goal of changing the permit restrictions on importation of true sugarcane seed.
1b.Approach (from AD-416):
Seed transmissibility of pathogens will be explored by conducting a series of crosses with diseased female clones. Plants will be inoculated with domestic sugar cane disease pathogens, including Leifsonia xyli subsp. xyli (Ratoon Stunting Disease –RSD), Xanthomonas albilineans, (leaf scald), Sugar Cane yellow leaf virus (SCYLV), and Sugar Cane mosaic virus (SCMV), and Sorghum mosaic virus (SrMV), induced to flower, and subsequently crossed to produce seed. In addition, seed will be collected from foreign sources which originated from plants infected with pathogens (e.g. phytoplasma) not found in the United States. Seedlings produced from the infected plants will be grown out and analyzed to determine the likelihood of transmitting disease through sugarcane seed. Seed containing pathogens not presently in the U.S. will be grown out in the federal sugarcane quarantine facility (APHIS) and other APHIS approved greenhouse and lab facilities (ARS) in Beltsville, MD. Seedlings obtained from crosses of pathogen infected parents will be analyzed using real-time polymerase chain reaction (PCR) or PCR analysis for the detection of disease pathogens and determination of transmission rates. If it is determined that the risk of transmission is low, steps will be taken to change APHIS regulations to allow importation of foreign seed and will alleviate industry fears regarding the introduction of exotic diseases. Ultimately, the importation of foreign seed will allow the United States access to germplasm containing valuable traits for use in domestic sugarcane breeding programs.
Seeds were collected from plants that were infected with sorghum mosaic virus, the causal agent of mosaic, or sugarcane yellow leaf virus, the causal agent of yellow leaf, or Xanthomonas albilineans, the bacterium that causes leaf scald. The seed were germinated and the resulting plants were examined to determine if the pathogens were transmitted through the seed to the next generation of plants. Of the diseases under study, none appeared to be transmitted through seed with the exception of Sugarcane yellow leaf virus. The progress of this study was monitored through the Sugarcane Crop Germplasm Committee. The researchers involved in this study presented their results during a conference call on February 24, 2012 and made a final report to the Sugarcane Crop Germplasm Committee on June 20, 2012.