The 'Group' letters/numbers that you see throughout this web site refer to the classification of herbicides by their site of action. To see a full list of herbicides and HRAC herbicide classifications click here.
QUIK STATS (last updated Jul 16, 2018 )
NOTES ABOUT THIS BIOTYPE
CROSS-RESISTANCE TO IMAZAPIC AND IMAZAPYR IN A WEEDY RICE (Oryza sativa) BIOTYPE FOUND IN MALAYSIA Biótipos de Arroz Vermelho (Oryza sativa) com Resistência Cruzada a Imazapic DILIPKUMAR, M.* e Imazapyr Encontrados na Malásia BURGOS, N.R. CHUAH, T.S. ISMAIL, S.
ABSTRACT - The Clearfield® rice production system is an effective management tool for weedy rice and other weeds in the direct-seeded rice culture. However, ifarmers cultivating the Clearfield rice disregard stewardship recommendations, the industry could face a problem of herbicide-resistant weedy rice which would occur through the selection of outcrosses. This study aimed to confirm imidazolinoneresistant weedy rice in Malaysia. The resistant weedy rice (R-WR) was found to be 67 fold more resistant to OnDuty® (premix of imazapic and imazapyr) than the susceptible weedy rice (S-WR) based on the GR50 values (rate that causes 50% inhibition of shoot growth). The Clearfield® rice cultivar was 32-fold more tolerant to OnDuty® than the S-WR. Furthermore, the R-WR was 54 and 89 fold more resistant to imazapic and imazapyr applied separately than the S-WR, respectively. The Clearfield® rice was 140- and 40-fold more tolerant to imazapic and imazapyr, respectively than the S-WR. The R-WR biotype was susceptible to non-selective herbicides glyphosate and glufosinate, as well as the selective graminicide quizalofop. Oxadiazon controlled the R-WR biotype, but pretilachlor was ineffective. The present study documented the first case of weedy rice that was cross-resistant to imazapic and imazapyr in Malaysian Clearfield® rice field.
* Corresponding author:
Received: August 8, 2017
Approved: August 15, 2017
Planta Daninha 2018; v36:e018182239
SOCIEDADE BRASILEIRA DA
CIÊNCIA DAS PLANTAS DANINHAS
1 Rice Research Centre, Malaysian Agricultural Research and Development Institute (MARDI), MARDI Seberang Perai,
13200 Kepala Batas, Pulau Pinang, Malaysia; 2 University of Arkansas, 1366 W. Altheimer Drive, Fayetteville, AR 72704, USA;
3 University of Malaysia Terengganu, 21030 Kuala Terengganu, Terengganu, Malaysia; 4 Universiti Kebangsaan Malaysia, 43600
UKM Bangi, Selangor, Malaysia.
ISSN 0100-8358 (print)
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.