Posts Tagged: greening disease

Some Genetic Resistance/Tolerance to HLB

Ed Stover and crew at USDA, Fort Pierce in Florida have been studying the response of different scions and rootstocks that have been inoculated with the HLB bacteria. As reported in the Proceedings of the International Citrus Conference (http://www.icc2016.com/images/icc2016/downloads/Abstract_Book_ICC_2016.pdf), they have found some scion/rootstock combinations more tolerant or less susceptible to the disease six years after they have been inoculated.  It turns out scions with a citron pedigree have more resistance.  Also those with a Poncirus (trifoliate) background also had lower populations of the bacterium. 

What this means is that there is resistance and possible immunity out there and there is breeding/genetic engineering material out there that can be used to improve the whole of the citrus family to HLB. Of course, this will take time, but there is hope.

Photos:

HLB symptoms and trifoliate leaves

HLB symptoms

trifoliate

Electronic “sniffer” for determining HLB

At a recent conference on Postharvest Technology Advances, Cristina Davis from the UC Davis Department of Mechanical and Aerospace Engineering presented information on the development of a device that can smell out trees infected with Huanglongbing (HLB).

Scientists at UC Davis are refining a mobile chemical sensor that can detect diseased citrus trees by sniffing their volatile organic compounds (VOCs). VOCs are emitted by all types of plants and contribute to their distinctive odors—such as the perfume of orange blossoms and pungent scent of garlic in the air. VOCs must exist at very high levels for humans to smell them, and there are some VOCs people cannot smell at all.  The machine is able to figure out the signature smells of HLB infected trees, sort of the way people evaluate wines with terms like “grassy”, “plum”, or “austere”, and distinguish them from  healthy or trees infected by other diseases.

Finding HLB-infected trees and eliminating them before Asian Citrus Psyllid (ACP) picks up the disease and spreads it to neighboring trees is a major challenge. The pathogen in the tree cannot be detected by leaf testing for three to nine months after infection, and the symptoms don’t show up in the tree for a year or more after infection. Meanwhile, the disease can be spread by ACP. Research is under way to develop early HLB detection so that infected trees can be rapidly removed.  Early detection will also allow researchers to more rapidly assess treatment programs for controlling not only the spread of the disease, but also possible cures or rootstocks or scion varieties that might have some resistance to the disease.

 

HLB infected tree showing mottling in one part of the canopy

HLB citrus

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