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Bioinstrumentation and BioMEMS Laboratory

Sensor System Development for Precision Agriculture

Plants emit back into the atmosphere a significant amount of their fixed carbon as volatile organic compounds (VOCs), which are associated with internal plant physiology changes. For example when plants are attacked by insects, the direct defense response is often to release volatile organic compounds, attracting insect predators. These emitted volatile compounds can also be referred to as induced VOCs (IVOCs). IVOCs are released from plants not only under biotic attack but also during abiotic stresses that can cause a temporarily increase of total carbon emissions.

The IVOCs appear to play an important role in plant-to-plant communication, herbivore defense, resistance to biotic stress and a host of other functions. The composition of the IVOCs, which number in the thousands, appears to contain information of the underlying biochemical processes on-going within the plants themselves. A hallmark of plant response is activation of several systemic signaling pathways that regulate expression of many genes, and thus which VOCs are liberated from the plant into the environment. Almost 1,700 volatile compounds have been isolated from more than 90 plant families and constitute ~1% of plant secondary metabolites. They include fatty acid and amino acid derivatives, terpenoids, phenylpropanoids, and others.

These volatile compounds are liberated into the environment from a variety of plant tissues, leaves, fruit, flowers, and roots. Many of these compounds act as long distance regulators of responses to pests, diseases, environmental stress, nutritional deficiencies, and other physiological events. These expressed VOCs can be monitored using analytical chemical sensors, through which we may gain insight from these observed metabolomic VOC phenotypes that represent a summation metabolic processes ongoing within a plant.

Measurement of the VOCs is therefore an attractive avenue for non-invasive monitoring of flowering, ripening, maturing, stress, and disease in plants - a host of biological "problems" that lack sufficient quantitative measurement tools.

Our research group is developing new portable VOC detection systems that can be used in the field to monitor plant VOCs for precision agriculture.


[from our paper: Dandekar AM*, Martinelli F, Bhushan A, Zhao W, Davis CE, Skogerson K, Fiehn O, Leicht E, D'Souza R. (2010) Non-destructive disease detection in citrus through the analysis of induced volatile organic compounds. Citrograph in press.]

The rapid and unabated spread of vector-borne disease within US specialty crops threatens our agriculture, our economy, and the livelihood of growers and farm workers. Early detection of vector-borne pathogens is an essential step for the accurate surveillance and management of vector-borne diseases of specialty crops. Currently, we lack the tools that would detect the infectious agent at early (primary) stages of infection with a high degree of sensitivity and specificity. Here we outline a strategy for developing an integrated suite of platform technologies to enable rapid, early disease detection and diagnosis of Huanglongbing (HLB), the most destructive citrus disease.

The research has two anticipated outcomes:

  • Identification of very early, disease-specific 'biomarkers' using a knowledge-base of translational genomic information on host and pathogen responses associated with early (asymptomatic) disease development; and
  • Development and deployment of novel sensors that capture these and other related biomarkers and aid in pre-symptomatic disease detection.


By combining these two distinct approaches, it should be possible to identify and defend the crop by interdicting pathogen spread prior to the rapid expansion phase of the disease. We believe that similar strategies can also be developed for surveillance and management of diseases affecting other economically important specialty crops.

[from our paper: Dandekar AM*, Martinelli F, Davis CE, Bhushan A, Zhao W, Fiehn O, Skogerson K, Wohlgemuth G, D'Souza R, Roy S, Reagan R, Lin D, Bruening G, Cary RB, Pardington P, Gupta G. (2010) Analysis of early host responses for asymptomatic disease detection and management of specialty crops. Critical Reviews in Immunology 30(3): 277-289.]

It is clear that technologies to diagnose plant diseases are sorely needed by commercial crop growers. A variety of diseases remain priority threats for the citrus and other agriculture industries. New sensors can play a key role in asymptomatically diagnosing these diseases for better crop management. [from our paper: Sankaran S, Mishra AR, Ehsani R*, Davis CE. (2010) A review of advanced techniques for detecting plant diseases. Computers and Electronics in Agriculture 72: 1-13.]

As one example of how our technology can work, we monitored VOCs emitted from healthy citrus fruit and those with a disorder termed "puff." We acquired gas chromatograph differential mobility spectrometry (GC/DMS) data from healthy and disordered fruit. We then deconstructed the signal space into a series of high-frequency and low-frequency domains using a technique termed wavelet analysis.


By examining unique features in the deconstructed signals, we were able to identify robust classification points in the signals to sort out disordered and healthy fruit using their VOC profiles.[from our paper: Zhao W, Sankaran S, Ibanez AM, Dandekar AM, Davis CE*. (2009) Two-dimensional wavelet analysis based classification of gas chromatogram differential mobility spectrometry signals. Analytica Chimica Acta 647: 46-53.]