Ploidy in <i>Lolium</i> spp. cultivars affects Argentine stem weevil parasitism by <i>Microctonus hyperodae</i>


  • F. Tomasetto AgResearch Ltd, Private Bag 4749, Christchurch 8140, New Zealand
  • O. Olaniyan Lincoln University, PO Box 85084, Lincoln 7647, New Zealand; University of Jos, Nigeria, P. M. B. 2084, Jos, Plateau State, Nigeria
  • S.L. Goldson AgResearch Ltd, Private Bag 4749, Christchurch 8140, New Zealand; Bio-Protection Research Centre, PO Box 85084, Lincoln University, Lincoln 7647, New Zealand



A laboratory study was conducted to: (1) advance earlier work to determine the susceptibility of Listronotus bonariensis (Argentine stem weevil) to its parasitoid biological control agent, Microctonus hyperodae, in the presence of diploid ryegrasses such as Lolium multiflorum or Lolium perenne; and (2) determine whether or not plant orientation (i.e. horizontal vs. vertical) had any effect on parasitism rates. No significant differences in parasitism rates were found in the Listronotus bonariensis populations in the two grasses. However, combining and analysing these data with those from an earlier experiment conducted in the same way showed that parasitism rates were significantly lower in diploid Lolium multiflorum cultivars than in tetraploid Lolium multiflorum. This is the first clear evidence of a ploidy effect on parasitism rates in the presence of Lolium multiflorum. Tetraploid Lolium multiflorum has fewer, more robust and larger tillers than the diploid Lolium spp. so higher parasitism rates may be related to the lack of hiding places for an evasive genetically-driven behaviourally-based resistance by Listronotus bonariensis.




How to Cite

Tomasetto, F., O. Olaniyan, and S.L. Goldson. “Gt”;. New Zealand Plant Protection 70 (July 31, 2017): 326. Accessed December 11, 2023.



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