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QUIK STATS (last updated Oct 19, 2016 )
NOTES ABOUT THIS BIOTYPE
Red rice (Oryza sativa) cross-resistance to imidazolinone herbicides used in resistant rice cultivars grown in northern Greece
Nikolaos S. Kaloumenos, Nieves Capote, Ana Aguado, Ilias G. Eleftherohorinos
Pesticide Biochemistry and Physiology 105 (2013) 177–183
A putative resistant red rice (Oryza sativa) accession, an imidazolinone-resistant rice cultivar (Clearfield), a susceptible red rice accession and a susceptible rice cultivar were evaluated for cross-resistance to imazamox and imazethapyr in a whole-plant response experiment and seed bioassay. Additionally, a 210-bp fragment of the ALS gene was sequenced to identify mutations responsible for resistance. Also, a 574 bp of the ALS gene was sequenced and PCR for detection of the ‘Clearfield allele’ was conducted by the Andalusian Institute of Agricultural Research and Training (IFAPA, Spain). In the whole-plant response experiment, the putative resistant red rice was >23 and >21 times more resistant to imazamox and imazethapyr than the susceptible accession, respectively, whereas the respective resistance factor values based on seed bioassay were 86.4 and 141.7. Also, the respective resistance factor values for the Clearfield rice cultivar were similar with those calculated for putative resistant red rice. Additionally, the sequence of the 210 bp ALS gene fragment from the putative resistant red rice and Clearfield rice cultivar revealed the same amino acid substitution of Ser653Asn in both alleles (homozygous). Furthermore, the sequence of a 574 bp ALS gene fragment and the PCR for detection of the ‘Clearfield allele’ confirmed that the putative resistant red rice is homozygous mutant for the Ser653Asn mutation and provided additional evidence that its genetic background matches that of Clearfield rice. These findings indicate clearly that the insufficient control of the putative resistant red rice with imazamox was due to target-site resistance and particularly due to a point mutation at the Ser653 codon, which is positively identified as having been derived from the Clearfield rice cultivar.
CONTRIBUTING WEED SCIENTISTS
Resistance to protoporphyrinogen IX oxidase (PPO)-inhibitors in Amaranthus palmeri and Amaranthus tuberculatus is mainly contributed by mutations in the PPO enzyme, which renders herbicide molecules ineffective. The deletion of glycine210 (∆G210) is the most predominant PPO mutation. ∆G210-ppo2 is overexpressed in rice (Oryza sativac. ‘Nipponbare’) and Arabidopsis thaliana (Col-0). A foliar assay was conducted on transgenic T1 rice plants with 2× dose of fomesafen(780 g ha−1), showing less injury than the non-transgenic (WT) plants. A soil-based assay conducted with T2 rice seeds confirmed tolerance to fomesafen applied pre-emergence. In agar medium, root growth of WT rice seedlings was inhibited 90% at 5μM fomesafen, while root growth of T2seedlings was inhibited by 50% at 45 μM fomesafen. The presence and expression of the transgene were confirmed in the T2rice survivors of soil-applied fomesafen. A soil-based assay was also conducted with transgenic A. thaliana expressing ∆G210-ppo2 which confirmed tolerance to the pre-emergence application of fomesafen and saflufenacil. The expression of A. palmeri ∆G210-ppo2 successfully conferred tolerance to soil-applied fomesafen in rice and Arabidopsis. This mutant also confers cross-tolerance to saflufenacil in Arabidopsis. This trait could be introduced into high-value crops that lack chemical options for weed management.