| Summary: | Peas suffer from several diseases, and there is a need for accurate, rapid in-field diagnosis. This study used proteomics to investigate the response of pea plants to infection by the root knot nematode Meloidogyne hapla, the root rot fungus Fusarium solani and the downy mildew oomycete Peronospora viciae, and to identify potential biomarkers for diagnostic kits. A key step was to develop suitable protein extraction methods. For roots, the Amey method (Chuisseu Wandji et al., 2007), was chosen as the best method. The protein content of roots from plants with shoot infections by P. viciae was less than from non-infected plants. Specific proteins that had decreased in abundance were (1->3)-beta-glucanase, alcohol dehydrogenase 1, isoflavone reductase, malate dehydrogenase, mitochondrial ATP synthase subunit alpha, eukaryotic translation inhibition factor, and superoxide dismutase. No proteins increased in abundance in the roots of infected plants. For extraction of proteins from leaves, the Giavalisco method (Giavalisco et al., 2003) was best. The amount of protein in pea leaves decreased by age, and also following root infection by F. solani and M. hapla at six weeks post-inoculation. F. solani caused a decrease in abundance of isocitrate dehydrogenase, glycerate dehydrogenase, carbonic anhydrase, oxygen evolving enhancer protein 2 (OEE2), phosphoglycerate kinase, chloroplastic and one unknown protein. Some leaf proteins increased in abundance, and included heat shock-related proteins (HSP70) and two unknown proteins. Proteins that decreased in leaves following root infection by M. hapla six week post-inoculation were RuBisCo large subunit, fructose bisphosphate aldolase 2, carbonic anhydrase, OEE1, OEE2, OEE3, RuBisCo small subunit and a 28KDa ribonucleoprotein. Some proteins increased in abundance, such as HSP70, fructose bisphosphate aldolase 1 and trypsin. In contrast to the decrease in protein observed at six weeks post-inoculation, the amount of protein increased in leaves three weeks after inoculation of roots with M. hapla. Root infection by both M. hapla and F. solani caused a reduction in leaf area, and also a reduction in fresh and dry weight of the shoot and root systems. The use of digital imaging and visible and infra-red light to study the changes in leaves was explored in this study. A clear difference was visible between leaves from healthy plants and between those from M. hapla and F. solani infected plants when imaged using a normal digital camera. In contrast, no clear differences were noticed between leaves of healthy, M. hapla and F. solani infected plants when using an infra-red camera with 850 nm wavelength light. This study indicates that specific proteins are altered in abundance in leaves following root infection, and provides the basis for future studies to develop rapid diagnostic tests.
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