October 20231. Please state project objectives and what work was done this quarter to address them:The objectives are to 2) determine if the flush cycle and infection period for Z. citri-griseum have changed due to the influence of HLB on citrus physiology or changing environmental factors; 4) evaluate the potential promotion of greasy-green symptoms related to nutrition programs or to peel reactions like a chemical burn from different pesticide and combinations of pesticide tank mixes; and 5) evaluate if postharvest degreening treatments might be modified to adequately remove the green coloration while mitigating poor shelf life from anticipated longer degreening times. Objective 2: To determine whether the flush cycle and infection period for Zasmidium citri-griseum have changed due to the influence of HLB on citrus physiology and other factors such as the changing environment, a site located in Fort Pierce was selected based on feedback from growers. Last year, two blocks with different grapefruit varieties were selected at the site for monitoring. Within each block, two groups of twenty mature grapefruit trees with similar canopy health status were selected and ten flush per tree was tagged. The same blocks were used for our second year of the field trial, which has been layed out. The data from last year’s experiment, including the flush cycle and fruit size, has been processed. Preliminary results of flush stage and fruit diameter per site (east and west) were assessed every two weeks using a shoot maturity index and caliper, respectively. In the summer flush cycle, there was a significant difference in the flush stage over time. Fruit size significantly increased over time starting in May (fruit size started above 3cm) as was expected. In the white grapefruit variety, fruit were slightly larger on the west side compared to the east side. Flush and fruit size data have been collected but are not yet analyzed from the second seaseon Evaluation of epiphytic growth on fruit and leaves is still ongoing. For the epiphytic growth on fruit, 210 slides were assessed, and the results suggest that epiphytic growth started in September on both white and red grapefruit which was unexpected. The complete set of samples was evaluated and in June and July, fewer than 40% of the leaf disks had spores. The percent leaf disks with spores rose to nearly 80% by August and remained near that level until December when sampling ended. Epiphytic grow the on leaf disks was present in June and July, but at very low levels around 0.01%. In August, this increased to approximately to 40% and remained at that level until December. When the trees were sampled, there were very few symptomatic leaves present in the grove, however greasy green symptoms were present on the fruit. We did not see many spores on fruit at the beginning of September this changed by mid-month. We expect this was a sampling issue. We found many more spores on the fruit than on the leaves at all the other dates until December. Epiphytic growth was present at all sampling dates and at approximately the same levels as on fruit. The current season’s leaf and fruit samples are being collected and processed. They have not been evaluated for epiphytic growth at this time but will be soon. We learned late last week that one of our blocks was harvested without prior notification. We have been working on developing species specific primers to confirm our identifications of spores on fruit. We have found some confusing results from some of our organismal sampling and wish to sort some of this out. We have the sequence required for this and target genes. Primer design is in progress and in silico testing is underway. It has revealed that some primers may need to be redesigned because of potential primer-dimers. Objective 4: We are also trying to meet with growers to compare programs from greasy-green affected and non- or less-affected blocks. The response is that there is not much difference between blocks. Some have indicated a willing to meet, but the actual dates for those meetings are still pending.I was unable to get an update for the report from the responsible Co-PI. Objective 5: We evaluated Red and white grapefruit from greasy-green affected blocks in January after initial degreening treatment in December. Degreening (with or without the cold treatment) significantly improved peel color after 5 days, however, even the best performing treatment was not very good (still negative a/b ratio). 4 treatments of each grapefruit type. Treatment 1: Straight into degreening room – degreen for 2 days (83F, 4 ppm ethylene) Treatment 2: Cold treat at 38F for 24 hrs. + degreen for 1 day (83F, 4 ppm ethylene)Treatment 3: Cold treat at 38F for 24 hrs. + transfer to ambient conditions without ethylene) – no degreeningTreatment 4: control (hold at ambient conditions without ethylene. (high humidity) For both types of grapefruit, treatments 1 and 2 had the greatest color change (P < 0.0001) although the a/b ratio was still negative, indicating a green color to the rind 5 days post-treatment. In February, we also evaluated color development of greasy-green Red and white fruit from the IMG blocks with different lengths of degreening. While degreening improved color, even after 20 days ambient storage, peel color was still not great . The data are still under analysis. No further data has been gathered since fruit are not mature yet this season. 2. Please state what work is anticipated for next quarter: The second season of field data in Fort Pierce will continue to be collected. Samples will be evaluated for epiphytic growth and should be matched with the flush data. A new season of post-harvest evaluations will be starting very soon as harvest has started. 3. Please state budget status (underspend or overspend, and why): No over or underspend on budget currently 4. Please show all potential commercialization products resulting from this research, and the status of each: None at this date.