|BRLANSKY, RONALD - University Of Florida|
Submitted to: Citrus Industry
Publication Type: Trade Journal
Publication Acceptance Date: 10/30/2015
Publication Date: 11/15/2015
Citation: Schneider, W.L., Roy, A., Hartung, J.S., Shao, J.Y., Brlansky, R. 2015. Citrus blight research. Citrus Industry. page 12-14.
Technical Abstract: With HLB now occurring throughout Florida citrus groves, citrus blight has been getting less attention even though the problem still exists. In fact, the combination of HLB and citrus blight has compounded the problem that the citrus industry is facing with decreased yields, small fruit size and tree loss. The presence of both diseases in groves and even in the same trees is now a common occurrence. Both diseases cause severe decline in the health and productivity of trees although the symptomology differs.Over the last two years our research on citrus blight, funded by the Citrus Research and Development Foundation, has shown the presence of virus sequences in blight affected trees and even in some healthy trees. These sequences are very similar to those of endogenous pararetroviruses. Viruses in this particular group have been found inserted into the genome of many plants without causing any noted disease. However when some other plants are exposed to certain stresses such as drought, pruning, changes in light intensity or flowering, the virus sequences may be activated, beginning infections that generate active virus genomes and often particles. When this happens in other pararetrovirus systems, the plant reacts to the virus with symptoms. It is quite possible this is also the case for the citrus blight pararetrovirus as well. In our work we have identified similar virus sequences both in the genome as well as outside of the genome of blight affected plants, consistent with the presence of an active pararetrovirus. In the spring of 2015 we took 250 samples from 50 blight-affected and healthy trees in groves in three different citrus growing areas of Florida. We have been able to detect the virus sequences in leaf samples. In the 250 samples active pararetrovirus was found in the leaves and roots of all of the blight affected trees but none of the healthy trees. We have also analyzed the sequence data sets of trees known to be affected by HLB and blight as compared with sequence data from healthy trees. We have identified a number of genes that are expressed at high levels in blight-affected, but not in healthy or HLB-affected trees. We are testing these preliminary results against the larger set of 50 trees sampled in the spring of 2015.