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Citrus huanglongbing disease is the greatest threat to the world citrus industry today. The cornerstone of disease control programs is the production of healthy grafted seedlings for transplantation into citrus groves, but it was not certain whether or not the pathogen can infect seed and be transmitted to seedlings. If this were the case, the disease control program would be compromised. This research was undertaken to determine whether or not the pathogen can be transmitted through seed. Fruit affected by citrus Huanglongbing were collected in Florida and seed obtained from them were grown in screened greenhouses in both Florida and Maryland. In Florida, the seedlings were maintained for 6-10 months, observed for symptoms and tested for the pathogen using the best testing method available. In Maryland the seedlings were observed for symptoms and tested repeatedly over the course of three years. Symptoms of huanglongbing were not observed in any of the 700 seedlings included in this study, even after 3 years of growth.
Nor were any of the diagnostic tests positive for the pathogen. Some sour orange seedlings in Beltsville displayed unusual growth and development. The unusual growth patterns were demonstrated to be associated with natural genetic recombination and not with infection by the pathogen. Thus no evidence of transmission of the citrus huanglongbing pathogen was obtained in this study and we conclude that the pathogen is not transmitted through seed. This research is of significance to the world-wide citrus industry. To obtain a full copy of the research publication Click here.
For more information about citrus pathogens please contact Dr. John Hartung
For more information concerning growing citrus please contact Cristina Paul