Molecular Methods for Plant Pest/Disease Detection

Indirect Method

Indirect Method-Biomarker based disease detection

• A biomarker is a measurable characteristic in a biological system which changes due to disease, exposure to chemicals or other factors

• Metabolite profiling– measurement of hundreds or potentially thousands

of metabolites– GC-MS (Gas Chromatography-Mass Spectrometry)

• Compounds are separated by GC and then transferred to the mass spectrometer for further separation and detection

Gas Chromatography-Mass Spectrometry (GC-MS)

Taiz, L & Zeiger, E. 2010. Plant Physiology. 5th Ed. Sinauer Associates, Inc., Publishers. Sunderland-USA.

Indirect Method-Plant properties/stress based detection

• Thermal imaging– straightforward choice for visualizing stress-induced

changes in leaf transpiration• Imaging spectroscopy – Non destructive– Vegetation has a very characteristic spectral reflectance,

or signature caused by chlorophyll absorption– Field based imaging techniques as an alternative to

traditional field survey methods for crop disease and pest monitoring

• Foc on cucumber• Digital infrared

thermography (DIT) was employed to detect changes in leaf temperature

• Temperature increased as leaves infected by Foc

• 10 dpi, necrosis and chlorosis appeared

• 11 dpi, leaf dehydration and wild developed http://www.sciencedirect.com/science/article/pii/S0981942812002690

Detection of Fusarium-damaged seeds using spectroscopy technique

• Quality control for wheat grain sorting

• Hyperspectral imaging (HSI) techniques

• Differentiation between 3 type of wheat seeds– Vitreous– Fusarium-damaged– Yellow berry

http://www.sciencedirect.com/science/article/pii/S1537511013000196

Things to consider

• It is important to remember that molecular diagnostic tests should be used with traditional methods. Molecular tests are not a replacement for the Plant or Insect Diagnostician, but are another tool in the diagnostic process.

• Samples should be examined by trained professionals whom can narrow down the list of possible diseases or pests affecting a given host.

• Molecular tests should complement traditional methods such as microscopy and culturing. Molecular tests are one component of the diagnostic process.