This resulted in the discovery of ten new microRNAs (miRNAs), along with 76 conserved miRNAs, and many small interfering miRNAs. Several of these sRNAs were found to have been induced specifically by HLB, which means that they can potentially be developed into early diagnosis markers for the disease. This is important because if trees can be diagnosed with HLB and treated before symptoms start to become apparent, then money spent by the global citrus industry on additional treatments might be saved.
In particular, miR399, which is induced by P starvation in other plant species, was discovered to be induced by HLB infection in the diseased citrus trees. It is known that miR399 is important for P translocation in plants by suppressing a P signalling pathway gene. The study found that the phosphorus level in leave of HLB-positive plants was on about 65% of that in healthy plants, suggesting that HLB is associated with P starvation in the citrus plants, which may in turn contribute to the expression of HLB symptoms.
Dr Jin writes, "we hypothesized that applying P solutions to the Las-positive trees would reduce HLB symptoms and improve tree performance." Phosphorus solutions were applied to HLB-positive sweet orange trees in a field trial three times per year for more than three years. Aft
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