Detecting Gene Flow From Als-Resistant Hybrid and Inbred Rice to Weedy Rice Using Single Plant Pollen Donors

Abstract

SUMMARYGene flow from herbicide-resistant rice (Oryza sativaL.) cultivars can affect the biodiversity ofOryzaspp. and can result in the lack of opportunity to control weedy rice through selective herbicides. The aim of the present study was to quantify the outcrossing rate from the herbicide-resistant red rice and rice cultivars carrying three different ALS (acetolactate synthase) alleles using a single plant pollen donor approach. A field experiment was performed using the encircle population combination technique. The main plots comprised the pollen-receptor IRGA 417 cultivar or a susceptible biotype of weedy rice, and the subplots comprised the pollen-donor inbred cultivars IRGA 422 CL and PUITÁ INTA CL, the hybrid SATOR CL or a resistant biotype of weedy rice. Among the pollen-donors, the outcrossing rate for pollen receptor susceptible weedy rice and the IRGA 417 cultivar was 0.0344% and 0.0142%, respectively. Rice cultivars carrying theALSgene mutations Ala122Thr, Ser653Asn and Gly654Asn showed a similar outcrossing rate of 0.0243%. The outcrossing rate decreased over a distance of up to 3.5 m from the pollen-donor and was not affected by the wind cardinal direction. The risk of gene flow of herbicide resistance from rice to weedy rice should be reduced through the development of new strategies to contain and mitigate gene flow and of the elimination of weedy rice escapees.

Status of weed control in imidazolinone-herbicide resistant rice in Rio Grande do Sul

“…However, even after 15 years using this system weedy rice is commonly found in the rice areas and is still reported as one of the most important problems of this crop mainly due to imidazolinone resistance. Despite the problems of herbicide resistance, Merotto Junior et al (2016) estimated that the utilization of the Clearfield ® System provided an increase of 2,000 kg ha -1 in rice yield due, mainly, to weedy rice control, better use of the fertilizers by the crop in comparison with weedy rice infested areas, and adequate timing of sowing in comparison with delayed seeding caused by two or three soil disk harrowings aimed at eliminating weedy rice.…”

“…Several factors have been related to the evolution of herbicide resistance in rice fields cultivated with the Clearfield ® system. The first herbicide resistance problem of this system was the occurrence of weedy rice resistance originated mainly from gene flow from the resistant rice varieties and spread through contaminated rice seeds (Goulart et al, 2016). After that, farmers became more conscious of the importance of using certified seeds, crop rotation, use of burndown herbicides at the S 3 plant stage (Counce et al, 2000), and use of imidazolinones at pre and post-emergence (Merotto Junior et al, 2016.…”

Snorkeling Strategy: Tolerance to Flooding in Rice and Potential Application for Weed Management

“…To achieve this, the transformed crop can be planted as pre-germinated seeds in shallow-flooded soil, allowing the establishment of the crop, but not the weedy rice outcrosses or volunteer GM rice. This approach will gradually eliminate weedy rice from the field, since gene flow from cultivated rice occurs at a rate of 0.03% or up to 1.26% with hybrid rice [53,54].…”

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

“…However, the large presence of isolated plants broadly distributed in rice fields raised the question of the magnitude of gene flow in this scenario. Therefore, a field study was performed based on a single pollen-donor plant in an encircled population combination technique with IMI-rice cultivars carrying all the different mutations as pollen donors and a rice cultivar and a weedy rice ecotype as pollen receptors (Goulart et al 2015). The use of a single donor plant in the center of an area of recipient plants favors the interpretation regarding situations where the resistant individuals may be derived from seed contaminants or where the resistance was originated from a spontaneous mutation in the ALS Whole-plant spraying…”

“…The combinations of pollen‐donor and pollen‐receptor plants and the necessary sample size resulted in the evaluation of approximately one million seeds (Goulart et al. ), which were evaluated through the seed soaking, whole‐plant herbicide spraying, and SNP molecular markers as described above (Fig. ).…”