Evolutionary and social consequences of introgression of nontransgenic herbicide resistance from rice to weedy rice in Brazil

Abstract

Several studies have expressed concerns about the effects of gene flow from transgenic herbicide‐resistant crops to their wild relatives, but no major problems have been observed. This review describes a case study in which what has been feared in transgenics regarding gene flow has actually changed biodiversity and people's lives. Nontransgenic imidazolinone‐resistant rice (IMI‐rice) cultivars increased the rice grain yield by 50% in southern Brazil. This increase was beneficial for life quality of the farmers and also improved the regional economy. However, weedy rice resistant to imidazolinone herbicides started to evolve three years after the first use of IMI‐rice cultivars. Population genetic studies indicate that the herbicide‐resistant weedy rice was mainly originated from gene flow from resistant cultivars and distributed by seed migration. The problems related with herbicide‐resistant weedy rice increased the production costs of rice that forced farmers to sell or rent their land. Gene flow from cultivated rice to weedy rice has proven to be a large agricultural, economic, and social constraint in the use of herbicide‐resistant technologies in rice. This problem must be taken into account for the development of new transgenic or nontransgenic rice technologies.

Weedy rice in sustainable rice production. A review

“…Since the adoption of Clearfield technology, weedy rice infestation has decreased in these areas. Up to 50% increases in rice production in Brazil due to Clearfield rice varieties have been reported (Merotto et al 2016). Significant increases in rice yield have been reported in Malaysia after Clearfield varieties were planted (Sudianto et al 2013).…”

“…These resistant varieties were found to have trait modifications in comparison to the historical weeds and cultivated varieties (Burgos et al 2014). In Brazil, weedy rice hybrids with several trait modifications appeared in rice fields after 3 years of Clearfield rice cultivation, which substantially increased the cost of rice production in Brazil (Merotto et al 2016). A study reported that the gene flow between Clearfield rice and weedy rice resulted in the generation of about 170 resistant plants per hectare (Shivrain et al 2007).…”

Little White Lies: Pericarp Color Provides Insights into the Origins and Evolution of Southeast Asian Weedy Rice

“…Weedy rice seedlings are often morphologically nearly identical to cultivated rice plants before they reach the reproductive stage, hindering detection and selective weeding. With a rapid growth rate, highly shattering seed, persistent seed dormancy, and dark, undesirable grains that contaminate harvests, weedy rice is considered one of the primary constraints on rice production and marketability in both temperate and tropical regions (Estorninos et al 2005; Gealy et al 2012; Merotto et al 2016). In addition, the potential for crop–weed gene flow threatens the long-term sustainability of weed control strategies that rely on herbicide-resistant rice cultivars (Pusadee et al 2013; Burgos et al 2014; Merotto et al 2016).…”

I Have a Dream: Organic Movements Include Gene Manipulation to Improve Sustainable Farming

“…First, as the phytoene synthase 2a gene is from the edible banana cultivar Asupina, any health reservation is not justified. Second, using infertile bananas excludes problems of transgene escape, in contrast to rice where outcrossing is a major problem [25].…”