P-170 - Development of Species-Specific Primers for Detecting Zasmidium citri-griseum in Citrus Fruit Exhibiting Greasy Green-like Symptoms in Florida

Greasy green is a citrus disorder in Florida characterized by green coloration on the fruit peel that is not removed by standard degreening practices. The fungal disease greasy spot-rind blotch (GSRB), caused by Zasmidium citri-griseum, presents similar fruit symptoms, but the typical foliar symptoms of GSRB are absent. While GSRB has historically caused defoliation and yield loss, greasy green is hypothesized to result from Z. citri-griseum infections exacerbated by environmental and physiological changes as well as management practices related to Huanglongbing. This study investigated the role of Z. citri-griseum in greasy green and developed a species-specific translation elongation factor (tef1-α) primer for its detection. 84 isolates from leaf litter collected from Florida groves were analyzed using a conventional polymerase chain reaction assay with genomic regions of the tef1-α gene of Z. citri-griseum. Of these, 28 isolates were successfully sequenced and compared with an ongoing study using universal fungal primers targeting the internal transcribed spacer, large subunit, and tef1-α for multilocus analysis. Flush development was recorded using a shoot maturity index, and fruit were degreened with 5 ppm ethylene and assessed for epiphytic fungal growth. Significant shoot growth (P < 0.05) and fungal growth were observed in both seasons. Detection of Z. citri-griseum using the tef1-α primer in symptomatic fruit and leaf samples will confirm its role in greasy green. The findings will clarify infection timing and improve disease diagnosis and management in Florida.