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Eighteen years of Clearfield™ rice in Brazil: what have we learned?
- Luis Antonio de Avila, Enio Marchesan, Edinalvo R. Camargo, Aldo Merotto, Jr., André da Rosa Ulguim, José Alberto Noldin, André Andres, Carlos H. P. Mariot, Dirceu Agostinetto, Sylvio H. B. Dornelles, Catarine Markus
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- Journal:
- Weed Science / Volume 69 / Issue 5 / September 2021
- Published online by Cambridge University Press:
- 30 July 2021, pp. 585-597
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Clearfield™ (CL) rice (Oryza sativa L.) is a weedy rice (Oryza spp.; synonym = red rice) control tool that has been used in Brazil since 2003. This system includes the use of an imidazolinone (IMI)-tolerant cultivar and the application of IMI herbicides. In this review article, Brazilian weed scientists evaluate the challenges and lessons learned over 18 yr of CL use. CL system benefits include selective weedy rice control, better crop establishment during the most advantageous period of the year, and more efficient fertilizer use. In Rio Grande do Sul state, the CL system, in conjunction with other improvements, has contributed to rice grain yield gains from 5,500 kg ha−1 before 2002 to around 8,400 kg ha−1 currently. In contrast, the main problem that has arisen over this period is the rapid evolution of IMI-resistant weedy rice, caused by gene flow from CL rice cultivars. The off-label use (rate and continuous use) of IMI herbicides has contributed to the evolution of resistance in Echinochloa spp. and other weeds. IMI herbicide carryover has also affected susceptible crops grown after CL rice. Crop rotation with soybean [Glycine max (L.) Merr.] is increasing, ensuring system sustainability. The importance of minimum tillage has also become apparent. Such cultivation includes applying nonselective herbicides before sowing or just before crop emergence (at the spiking stage to eliminate as much weedy rice as possible and other weeds at an early growth stage). It also includes the use of certified seeds free of weedy rice, following label instructions for IMI herbicides, applying the herbicide PRE followed by POST, and complementary weedy rice management practices, such as roguing of surviving weedy rice plants.
Weedy rice (Oryza spp.) diversity in southern Brazil
- Leonard Bonilla Piveta, José Alberto Noldin, Nilda Roma-Burgos, Vívian Ebeling Viana, Lariza Benedetti, Jesus Juares Oliveira Pinto, Fabiane Pinto Lamego, Luis Antonio de Avila
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- Journal:
- Weed Science / Volume 69 / Issue 5 / September 2021
- Published online by Cambridge University Press:
- 22 March 2021, pp. 547-557
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Weedy rice (Oryza spp.) is one of the most troublesome weeds affecting rice (Oryza sativa L.) production in many countries. Weedy rice control is difficult in rice fields, because the weed and crop are phenotypically and morphologically similar. Weedy rice can be a source of genetic diversity for cultivated rice. Thus, this study aimed to characterize the morphological diversity of weedy rice in southern Brazil. Qualitative and quantitative traits of 249 accessions from eight rice-growing mesoregions in Rio Grande do Sul (RS) and Santa Catarina (SC) states were analyzed. For each accession, 24 morphological descriptors (14 qualitative and 10 quantitative) were evaluated. All 249 accessions from RS and SC are of indica lineage. Considering all the phenotypic traits evaluated, the accessions separated into 14 distinct groups. One of the largest groups consisted of plants that were predominantly tall with green leaves, intermediate shattering, and variable flowering time. Distinct subgroups exist within larger clusters, showing discernible phenotypic diversity within the main clusters. The variability in flowering time was high (77 to 110 d after emergence), indicating high potential for flowering synchrony with rice cultivars and, consequently, gene flow. This indicates the need to remove escapes when planting herbicide-resistant rice. Thus, weedy rice populations in southern Brazil are highly diverse, and this diversity could result in variable response to weed management.
Status of weedy rice (Oryza spp.) infestation and management practices in southern Brazil
- Luis Antonio de Avila, José Alberto Noldin, Carlos H. P. Mariot, Paulo F. S. Massoni, Marcus V. Fipke, Vinicios R. Gehrke, Aldo Merotto, Jr, Flavia M. Tomita, André B. Matos, Gelson Facioni, Edinei B. Vieira, Eduardo S. Rosa, Roger P. Santis, Edinalvo R. Camargo, Giovani Theisen, Nilda Roma-Burgos
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- Journal:
- Weed Science / Volume 69 / Issue 5 / September 2021
- Published online by Cambridge University Press:
- 22 March 2021, pp. 536-546
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Weedy rice (WR) (Oryza spp.) is the most troublesome weed infesting rice paddies in Brazil. Several changes have occurred in this region regarding crop management, especially WR control based on the Clearfield® (CL) rice production system launched in 2003. This survey’s objective was to evaluate the WR infestation status by assessing the producers’ perception and the management practices used in southern Brazil after 18 yr of CL use in Brazil. Rice consultants and extension agents distributed a questionnaire to 213 producers in the Rio Grande do Sul (RS) and Santa Catarina (SC) states in the 2018 to 2019 growing season. In RS, most farms are larger than 150 ha, and farmers have adopted the CL system for more than 2 yr and use minimal or conventional tillage, permanent flooding, clomazone PRE tank-mixed with glyphosate at the rice spiking stage, and crop rotation with soybean [Glycine max (L.) Merr.] or pasture. In SC, rice farms are small, averaging from 20 to 30 ha, farmers predominantly plant pre-germinated rice and do not rotate rice with other crops, and roguing is practiced. Comparing both states, the CL system is used in 99.5% and 69.3% of the total surveyed rice areas in RS and SC, respectively. Imidazolinone-resistant WR is present in 68.4% and 26.6% of rice farms in RS and SC, respectively. Rice cultivation in Brazil is currently coexisting with WR with minimal integration of control methods. However, integrated practices can control this weed and are fundamental to the sustainability of systems based on herbicide-resistant rice cultivars.