From the Clearfield® to the Provisiatm system for rice production: Challenges and management opportunities

Abstract

Background: The development of imidazolinone-resistant rice (Clearfield®) enabled selective weedy rice control. However, the evolution of imidazolinone(IMI)-resistant weedy rice (WR-R) made this system ineffective for weedy rice control. Provisia™ rice was developed as an alternative to Clearfield® rice to sustain rice production. Objective: This review addresses the challenges and management opportunities of using Provisia™ rice, especially regarding: 1) gene flow; 2) strategies to reduce IMI-resistant weedy rice soil seedbanks; 3) imidazolinone herbicide carryover; and 4) herbicide tank mixing. Results: The rapid evolution of WR-R is mainly attributed to pollen-mediated gene flow between Clearfield® rice varieties and weedy rice. Therefore, to avoid the same problem from happening to Provisia™ technology, it is crucial to mitigate (or delay) the evolution of quizalofop- resistant weedy rice. IMI-resistance associated with some weedy rice traits has allowed the increase of WR-R soil seedbanks. Thus, strategies are necessary to hinder the development of WR-R soil seedbanks, such as alternating soybean and Provisia™ rice. The IMI persistence and soil residual activity can reduce the grain yield of non-CL rice (such as Provisia™ rice). Therefore, detection of IMI soil concentration at levels with potential reduction of rice grain yield or herbicide safeners can help guide the transition from Clearfield® to Provisia™. Quizalofop has a narrow weed control spectrum, requiring herbicide tank mixing, so the choice of the tank-mix partner will be critical to avoid plant escape. Conclusions: The correct management of this new technology, considering the topics covered, can contribute to extend the use of Provisia™ and revive the use of Clearfield® rice.