Plant Gene and Traits 2024, Vol.15, No.4, 162-173 http://genbreedpublisher.com/index.php/pgt 163 Glufosinate is a broad-spectrum herbicide used to control a wide range of weeds, including weedy rice. The development of glufosinate-tolerant rice varieties has been a focus of research to enhance weed management in rice fields. Studies have shown that certain weedy rice accessions exhibit reduced sensitivity to glufosinate, indicating potential for breeding glufosinate-tolerant rice (Shrestha et al., 2019). However, the bidirectional gene flow between transgenic glufosinate-resistant rice and weedy rice raises concerns about the emergence of herbicide-resistant weedy rice populations, which could pose significant agro-ecological risks (Chen et al., 2004; Lu et al., 2014; Zhang et al., 2018; Shrestha et al., 2020). The agronomic performance of hybrids between weedy rice and transgenic glufosinate-resistant rice suggests that gene flow from cultivated rice to weedy rice can occur under natural conditions, further complicating weed management (Song et al., 2011). This review aims to evaluate the breeding potential of glufosinate-tolerant rice accessions for developing herbicide-resistant rice varieties, assess the challenges associated with the introgression of glufosinate tolerance from weedy rice to cultivated rice, investigate the genetic diversity and agronomic performance of weedy rice accessions with varying levels of glufosinate tolerance, and explore the implications of gene flow between transgenic glufosinate-resistant rice and weedy rice on weed management and rice production sustainability. By addressing these objectives, this review hope to provide insights into the potential and challenges of utilizing weedy rice in breeding programs for herbicide-resistant rice, contributing to more effective and sustainable weed management strategies in rice cultivation. 2 Background on Weedy Rice 2.1 Characteristics and distribution Weedy rice is a significant weed in rice cultivation, known for its competitive traits that make it more resilient and persistent than cultivated rice. These traits include rapid growth, high tillering, enhanced fertilizer uptake, asynchronous maturation, ease of shattering, and high seedbank longevity (Nadir et al., 2017; Shrestha et al., 2019). Weedy rice is found in rice-growing regions worldwide, with its distribution closely linked to areas where rice is cultivated (Figure 2) (Nadir et al., 2017). The first reference to weedy rice in the literature was reported by Biroli in 1807 and its occurrence in the USA was reported in 1898 (Nadir et al., 2017). In Korea, weedy rice was observed in 1916, where it was called “sharebyeo” by local farmers. A representative type of weedy rice is “Lu-tao” in China, which was commonly found in the lower Yangtze River (Anhui and Jiangshu provinces) (Chen and Suh, 2015). The presence of weedy rice is particularly problematic in regions that have adopted direct seeding methods, as opposed to traditional transplanting, which had been more effective in controlling weedy rice populations (Gressel and Valverde, 2009). Figure 2 Global distribution of weedy rice. The red circles denote the regions where weedy rice has been reported (Nadir et al., 2017)
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