Abstract
ABSTRACT: The appearance of soybean cultivars that are tolerant to herbicides from the imidazolinone group enables irrigated rice rotation conducted on Clearfield® system. The objective of this work was to evaluate the morphological and metabolic changes of soybean cultivars containing Cultivance® (CV), which is tolerant to imidazolinone, sulphonylurea toletant (STS) and Roundup Ready® (RR), which is tolerant to glyphosate as affected by carryover of increasing doses of imazapyr and imazapic herbicides mixture, applied in the management of irrigated rice crop. Thus, experiments were conducted on the field and in greenhouse, evaluating phytotoxicity, height, leaf area, shoot dry matter, as well as variables related to the secondary metabolism of plants like chlorophyll, carotenoids, hydrogen peroxide, lipid peroxidation and electrolytes leakage. Soybean cultivars RR and STS are susceptibles to the carryover of imazapyr and imazapic mixture applied in the management of irrigated rice crop, whereas the CV cultivar is resistant. The rise in the herbicide carryover dose increases the reactive oxygen species (ROS) production in soybean plants. The RR cultivar, in general, shows higher ROS production compared to the other soybean cultivars.
Highlights
Herbicides from the imidazolinone group are effective to control a wide spectrum of weeds; they are used in commercial mixtures, such as imazapyr+imazapic to control red rice, cultivated with the Clearfield® system
As for the herbicide doses, data referring to cultivar Roundup Ready® (RR) did not adjust to any model which biologically explained its behavior
A linear increase in the phytotoxicity was observed as the dose increased; a double increase was verified in the variable for each added herbicide unit for the cultivar STS, compared to CV
Summary
Herbicides from the imidazolinone group are effective to control a wide spectrum of weeds; they are used in commercial mixtures, such as imazapyr+imazapic to control red rice, cultivated with the Clearfield® system. The rice/soybean rotation provides different advantages, since as well as facilitating the control of red rice, it allows a better use of soil resources. The rise of new technologies, such as Cultivance®, is an alternative for the management of red rice in areas with carryovers of herbicides from the imidazolinone group. These herbicides act inhibiting the acetolactate synthase enzyme (ALS), which act on the first step of the synthesis of the branched chain amino acids valine, leucine and isoleucine. The incapacity of cells to produce these amino acids causes cell death, since they are fundamental for the synthesis of proteins and derivates, as well as being essential for other metabolic routes
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