Sess08 7 lucy moleleki   soft rot enterobacteria and root knot nematodes - two emerging pathogens of potatoes
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Sess08 7 lucy moleleki soft rot enterobacteria and root knot nematodes - two emerging pathogens of potatoes






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    Sess08 7 lucy moleleki   soft rot enterobacteria and root knot nematodes - two emerging pathogens of potatoes Sess08 7 lucy moleleki soft rot enterobacteria and root knot nematodes - two emerging pathogens of potatoes Presentation Transcript

    • Soft Rot Enterobacteria and Root Knot Nematodes:Two Emerging Pathogens of Potatoes Lucy Moleleki University of Pretoria
    • Background South African potato production is approximately 50 000 ha ◦ There are 16 potato producing regions ◦ The different sectors are seed, table, export and processing Like other crops, potatoes are susceptible to many pests and pathogens including fungi, nematodes, bacteria and viruses. Clean seed is crucial for successful potato production. The advent of PCR-based methods in identification – Focus on Root Knot Nematodes and Soft Rot Enterobacteriaceae.
    • Root Knot Nematodes (Meloidogyne spp) • The ability to identify and distinguish these different species is important for implementation of appropriate control majors, crop rotations, resistant cultivars and for quarantine purposes. • Traditionally, Root knot nematodes are identified and distinguished based on morphology, but this can be difficult for non specialist • Difficulty in identifying emerging highly virulent species such as M. enterolobii • Seed tubers may have low levels of RKN and no apparent symptoms. • There is a need for a sensitive, rapid and accurate method of RKN detection and identification.
    • Soft rot enterobacteria (SRE) Formerly known as Erwinia spp The former E. carotovora has now been reclassified as Pectobacterium spp and the former E. chrysanthemii is now Dickeya spp. There are five Pectobacterium species but the use of PCR based methods has facilitated identification of new and novel species. Dickeya spp are divided into six species and several pathovars, D. solani is a highly aggressive new novel species that has now been identified in Europe and Israel. Therefore it is important to constantly utilise molecular based techniques to screen for presence of these aggressive species.
    • Approach mdh gapA genebank
    • Interaction between SRE and RKN Both RKN and SRE pose a significant threat to potato production. There are no effective chemical treatments for SRE and systemic nematicides are being withdrawn from the market. It is likely that RKN populations will grow in the rhizosphere. Nematodes are known to form synergies and complexes with other pathogens in the soil increasing diseases incidences of those pathogens.
    • bacteria • Rhizosphere interactions • Nematodes are relatively large • repeated thrusting causes wounds and mechanical damage • RKN also form complexes with other pathogens • RKN and Ralstonia solanacearum • RKN and Alternaria alternata • Increased disease severity
    • One of the challenges in establishing whether an interaction exists between two pathogens is the dependence on symptoms as a measure of such interactions We developed fluorescent protein tagged strains of soft rot enterobacteria to establish interaction with root knot nematodes
    • RKN wounds increase SRE in planta
    • Potato resistance to SRE and RKN Resistant cultivars for SRE and the RKN present a desirable alternative over harmful chemicals We screened potato cultivars for resistance to blackleg disease A B
    • C D E A B
    • Kubheka, G., Coutinho T., Moleleki N and Moleleki L (2013) Phytopathology Accepted for publication F G H I
    • Summary and concluding remarks The use of PCR based detection systems indicated presences of two Pectobacterium spp: More screening is still necessary P. wasabiae and P. brasiliense A comprehensive survey of RKN in potatoes identified five Meloidogyne spp including the highly virulent M. enterolobii. The interaction between RKN and SRE in vitro and in planta using fluorescent tagged SRE was demonstrated. There is a need to study interactions between RKN and other pathogens using a similar system. A cultivar with resistance to blackleg was identified and differences in colonisation of the SRE on the susceptible and resistant cultivars were observed. Trials to determine if this cultivar is resistant to RKN or combined infections between RKN and SRE are ongoing.
    • Acknowledgements