Spatial and temporal evolution of imidazolinone-resitant red rice in 'Clearfield' rice cultivations

Abstract

The objective of this work was to evaluate the distribution of imidazolinone-resistant (IMI-R) red rice (Oryza sativa) populations, the frequency of alleles conferring resistance to IMI, and the adoption of agronomic practices applied to red rice control, across growing seasons and production regions of the state of Rio Grande do Sul (RS), Brazil. In the experiment, 1,008 red rice populations were screened for resistance to IMI, 760 IMI-R red rice plants were genotyped for the acetolactate synthase (ALS) alleles conferring resistance to IMI, and 40 'Clearfield' rice growers were surveyed. IMI-R red rice populations were widespread throughout RS since the 2006/2007 growing season, with a higher initial frequency in the Depressão Central and Fronteira Sul production regions. The occurrence of IMI-R red rice ranged from 1.6 to 3.5 years after 'Clearfield' rice release. Gly654Glu was the most frequent ALS mutation in IMI-R red rice populations, which shows a gene flow from the most used 'Clearfield' rice cultivars to the red rice plants. Crop rotation systems and certified seed were used by only 30% of the surveyed growers of 'Clearfield' rice, with lower percentages in the production regions where IMI-R red rice appeared faster.

Eighteen years of Clearfield™ rice in Brazil: what have we learned?

“…In Brazil, resistant weedy rice was detected 3 to 4 yr after adoption of the CL rice production system (Merotto et al 2016). A long-term study conducted between 2006 and 2012 found resistant weedy rice in 56% to 100% of the analyzed suspected populations (Kalsing et al 2019), indicating the high occurrence of IMI-resistant weedy rice in rice cultivation in southern Brazil. Gene flow was the primary origin of IMI-resistant weedy rice, but independent selection occurred in 1.1% of the weedy rice plants evaluated, a frequency similar to that in other weeds subject to herbicide selection pressures (Goulart et al 2012).…”

“…The continuous use of CL rice, the lack of diverse herbicide MOAs, and higher herbicide rates are factors that contribute to more frequent weed resistance to ALS-inhibiting herbicides in rice farms. In general, few growers adopt herbicide rotation to minimize the evolution and spread of weed resistance to herbicides (Kalsing et al 2019; Norsworthy et al 2013).…”

First Report of Herbicide-Resistant Echinochloa crus-galli in Uruguayan Rice Fields

“…In addition to this, an increase in the presence of red rice (Oryza sativa L.), especially in long rice-history systems, has also prompted the augmentation of the use of Clearfield technology [20]. Although a strong stewardship program existed, not all of the management recommendations have been followed in all situations, resulting in higher risks of selecting E. crus-galli biotypes resistant to imazapyr + imazapic (IMIS), in addition to resistant red rice [21,22]. It is an open secret that most farmers do not apply preventive measures unless they face the problem personally [23,24].…”

Off-season management with herbicides as an alternative to reduce weed infestation in paddy rice production systems

“…The non-chemical control methods are usually laborious and expensive, and weedy rice is easily dispersed along with the seed of cultivated rice, also establishing a persistent seed bank (Chin, 2001). So, the management of this weed should be based on integrated practices (Watanabe, 2011), which include using high-purity certified seeds, previous preparation of the soil, rotation of production systems (Kalsing et al, 2019), a fast establishment of the ponding water depth (Avila et al, 2005), and application of herbicides in presowing (Noldin et al, 2002).…”