Low-Cost Sampling Approaches for Measuring Induced VOCs of Citrus

Huanglongbing (HLB) is a pathogen that devastates citrus crops; growers and public response agencies need a portable, sensitive, in-field device to detect this pathogen in citrus crops. However, there are no low-cost, robust diagnostic tests currently available for early identification of this or other citrus pathogens under field conditions. Quantitative polymerase chain reaction (qPCR) testing is the current regulatory decision-making standard for detection of HLB in citrus. qPCR has an evidence-based threshold value that is conservative enough to avoid excess false positives that could undermine trust. However, for decision-making by a grower, qPCR is not ideal. Early diagnosis is difficult to achieve because of highly non-uniform distribution of the bacteriumin a tree and there are seasonal and cultivar variations in bacterial llevels.There are strong motivations to find diagnostic processes that are based on changes in the plant that are induced systemically throughout the plant, making sampling less problematic. This programdirectly responds to the need to reduce the impact of plant pathogens and insect pests on citrus crops by developing a means of early detection. One approach that we are taking is analysis of the odor provide of healthy and diseased trees. We will develop an odorsampling protocol that will be low-cost and user-friendly, applicable to both grove owners as well as residential owners who have citrus on their residential property. We propose to develop a sampling technology and process that does not require highly-trained technicians and expensive equipment. This program will develop robust HLB signature libraries targeting accuracies of 0.9 or better on a tool that will have high throughput and be automated for low-cost operation (about 1/3 the cost of current qPCR testing).