Browsing by Author "Ghani Zadeh, Hossein"

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    Aspects of herbicide resistance in three New Zealand weed species : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Science at Massey University, Manawatu, New Zealand
    (Massey University, 2015) Ghani Zadeh, Hossein
    Herbicide resistant weeds have become a challenge in agricultural systems globally. In this thesis, aspects have been studied of three weed species which have evolved resistance to herbicides from different chemical families within New Zealand. Dicamba-resistant fathen (Chenopodium album) was recently reported by researchers in Waikato. In this thesis, the level of resistance to dicamba in two of these populations of fathen was investigated using a whole plant dose-response experiments and it ranged from 5- to 20-fold. Also, a seed-test for rapidly and reliably detecting dicamba resistant fathen has been developed. Seed tests have seldom been used for detecting resistance within weeds to auxinic herbicides. The thesis also investigated aspects of the first reported cases of glyphosate resistance in New Zealand, found in both Italian ryegrass (Lolium multiflorum) and perennial ryegrass (Lolium perenne) from vineyards. Resistance to glyphosate in two populations of Italian ryegrass (Populations A and P) and two populations of perennial ryegrass (Populations J and N) was found to be almost 10-fold, whereas it was almost 30-fold for one perennial ryegrass population (Population O). Three different quick tests (seed assays, excised tiller bioassays and shikimic acid assays) were developed for detecting glyphosate resistance in Italian ryegrass and perennial ryegrass. Of the five populations of ryegrass studied, only Population O had a target site modification at Codon 106 of the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). Translocation of radiolabelled glyphosate was studied in four of the populations (Populations A, J, O and P), and movement from treated leaves was significantly reduced in them all compared with susceptible populations (non-target site mechanism of resistance). Therefore, Population O had two mechanisms of resistance, possibly explaining the 30-fold resistance. The studied glyphosate-resistant ryegrass populations were all found to be resistant to glufosinate. Populations A, J and O were also found to be resistant to amitrole. Genetic studies showed that the restricted glyphosate translocation trait is incompletely dominant and can be transmitted via pollen. The restricted herbicide translocation was suppressed under cool conditions in experiments, suggesting that application of glyphosate during winter might improve control of glyphosate-resistant Italian ryegrass and perennial ryegrass infestations. KEYWORDs: Chenopodium album, dicamba, glyphosate, Lolium multiflorum, Lolium perenne, amitrole, glufosinate, glyphosate mechanisms of resistance, target site mechanism of resistance, restricted herbicide translocation.