Rice, serving as a staple food for over half of the global population, faces significant challenges within its farming system. The most notable issues are weed management, disease control, biotic-abiotic stress, and climatic change. Among these challenges, the issue of weeds, particularly weedy rice (Oryza sativa L., red rice), stands out as a crucial problem, reducing both rice grain yield and quality. The conventional approach of applying herbicides is the common method for weed control, however, it is increasingly losing efficacy due to various factors year by year. This chemical-based weed control method is not only labor-intensive and expensive but also raises environmental concerns when applied repeatedly. On the other hand, since weedy rice is taxonomically classified as the same species as cultivated rice, its chemical control is very difficult. The development of herbicide-resistant rice systems such as Clearfield®, Provisia®, and Roxy® RPS helps manage weedy rice. However, Clearfield® began losing effectiveness soon after its introduction due to gene flow and misuse. Provisia® was introduced in 2018 but few countries utilized it up to now. Roxy® RPS is not yet available in the EU. Recognizing the potential deterioration of these systems, it becomes imperative to establish new resistance resources for deployment by European countries. Our objective was to create a novel herbicide-resistant source of rice and make it available to European farmers in the future. We developed low-dose resistant rice materials but did not achieve high-dose resistance at the commercial level. The project involved launching a new cross-breeding program intended for use in EU countries. This program focused on cross-breeding low-dose clethodim-resistant base material with various EU national rice varieties. The objective of this new breeding program is to contribute to effective weed management in rice fields for rice-growing countries within the European Union.
The project also attempted to model the potential lifetime of Clearfield® technology. For this purpose, surviving weedy rice samples were collected from fields where Clearfield® rice varieties were produced, and as a result, it was determined that there was a 22% gene flow from Clearfield varieties to weedy rice. This point, reached in a 10-year period of use in Türkiye, where is considered as a model country, reveals that the technology may become dysfunctional in the near future. These results clearly revealed the importance of the subject which new herbicide-resistant rice technologies are needed to create a diverse weedy rice management method available for rice production and move towards sustainable rice farming.
