Response of imidazolinone-resistant and -susceptible weedy rice populations to imazethapyr and increased atmospheric CO2

Claudia Oliveira,Leonard B. Piveta,Luis A. Avila,Nilda Roma-Burgos,João P. Refatti,José A. Noldin

doi:10.1590/s0100-83582020380100078

Abstract

Abstract Background: Weedy rice (Oryza sativa L.) is the main weed of rice crop. The high genetic variability of weedy rice contributes to the high phenotypic diversity between biotypes and different responses to environmental stress. Objective: The present study aimed to evaluate the response of imidazolinone-susceptible and -resistant weedy rice populations to increased atmospheric [CO2]. Methods: The experiment was arranged in a complete randomized design with six replications. The treatments included two [CO2] concentration (700 and 400 μmol mol-1) and three treatments: resistant genotype (IMI-resistant) treated with imazethapyr; resistant genotype without imazethapyr, and a susceptible genotype without imazethapyr. Results: The IMI-resistant and -susceptible weedy rice responded similarly to [CO2] enrichment. Enhanced [CO2] increased competitive ability of the weedy rice populations tested, by means of increased plant height. Weedy rice seed production also increased with enhanced [CO2] by means of increased photosynthesis rate and reduced transpiration (increased water use efficiency). Increased seed production also means increased weed persistence as it increases the soil seedbank size. The application of imazethapyr on IMI-resistant weedy rice did not alter its response to [CO2]; conversely, increased [CO2] did not change the resistance level of weedy rice to imazethapyr. High [CO2] increased spikelet sterility, but this beneficial effect was negated by the overall increase in production of filled grains. Conclusions: Enhanced [CO2] concentrations increases weedy rice growth, photosynthesis rates, seed production and spikelet sterility; the imidazolinone application does not affect the response of weedy rice to enhanced [CO2] affects weedy rice response to imidazolinone herbicide.

Highlights

The atmospheric carbon dioxide concentration [CO2] reached 400 μmol mol-1 in 2017 (NOAA, 2017), representing an increase of over 25% since 1960
Plant height was not affected by [CO2] at the beginning of the growing season but starting at about 80 DAE, the plants were taller under elevated [CO2] (700 μmol mol-1) compared to those in ambient [CO2] (400 μmol mol-1) regardless of genotype or herbicide treatment (Figure 1)
The IMI-resistant and -susceptible genotypes both grew taller under elevated [CO2], and were of the same height during most of the vegetative stage, the final heights (119 DAE) of the resistant and -susceptible weedy rice were 19.2 and 28.7% greater, respectively, when grown under elevated [CO2], compared to plants in ambient [CO2]

Summary

Introduction

The atmospheric carbon dioxide concentration [CO2] reached 400 μmol mol-1 in 2017 (NOAA, 2017), representing an increase of over 25% since 1960. The Intergovernmental Panel on Climate Change (IPCC) estimates that, by the end of the 21st century, global climate changes caused by emission of greenhouse gases will lead to an increase in atmospheric [CO2] above 700 μmol mol-1 (IPCC, 2014). Such condition will cause major changes on the earth’s climate, which will drive changes in agricultural zoning, methods of crop management, and crop yields (Wang et al, 2017). Weedy rice seed production increased with enhanced [CO2] by means of increased photosynthesis rate and reduced transpiration (increased water use efficiency). Conclusions: Enhanced [CO2] concentrations increases weedy rice growth, photosynthesis rates, seed production and spikelet sterility; the imidazolinone application does not affect the response of weedy rice to enhanced [CO2] affects weedy rice response to imidazolinone herbicide

Objectives

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Conclusion