Abstract
Herbicide resistance is a worldwide problem in weed control. This prompts researchers to look for new modes of action to slow down the evolution of herbicide-resistant weeds. This research aims to determine the herbicidal action of thiazolo[3,2-a]pyrimidines derivatives, which are well known as antihypertensive drugs. The phytotoxic effects of ten compounds were investigated using leaf disc discoloration test and seed germination bioassay. At concentrations of 125 to 250 mg/L, the 5-(3-Fluoro-phenyl)-7-methyl-5H-thiazolo[3,2-a]pyrimidine-6-carboxylic acid ethyl ester (c) was highly active against Oldenlandia verticillata and Eleusine indica. At application rates of 1.25 to 2.5 kg ai/ha, formulated c demonstrated selective post-emergence and pre-emergence herbicidal activity against O. verticillata, E. indica and Cyperus iria. In the crop tolerance test, formulated c outperformed the commercial herbicide diuron, with aerobic Oryza sativa being the most tolerant, followed by Zea mays, and Brassica rapa. The addition of calcium chloride partially nullified compound c's inhibitory effects on weed shoot growth, indicating that it has potential as a calcium channel blocker. Compound c acted by triggering electrolyte leakage without affecting photosystem II. These findings imply that c could be explored further as a template for developing new herbicides with novel modes of action.
Highlights
Herbicide resistance is a worldwide problem in weed control
It is reasonable that compound c exerted greater inhibition on the roots than shoots (Table 1), as shown by the study of Bourgou et al.[27], where greater inhibitory effects of the phenolic compounds were observed on roots if compared to shoots
Diuron fully inhibited the shoot growth of O. verticillata at the beginning first week of all treatments, the seedlings treated by compound c was still able to grow. They gradually wilted and died after 3 weeks of treatment. These findings indicate that when introduced to O. verticillata seedlings, the phytotoxicity of c is comparable to that of diuron (Fig. 4)
Summary
Herbicide resistance is a worldwide problem in weed control. This prompts researchers to look for new modes of action to slow down the evolution of herbicide-resistant weeds. Compound c acted by triggering electrolyte leakage without affecting photosystem II These findings imply that c could be explored further as a template for developing new herbicides with novel modes of action. Thiazolopyrimidine, an example of calcium channel blocker, has been of interest due to their well-known biological and medicinal activities[18,19,20,21,22,23,24,25]. Despite their wide range of pharmacological activities, there is a lack of information regarding the phytotoxic behaviour of these fused pyrimidine derivatives. This study aimed to screen for the promising thiazolopyrimidine derivatives and evaluate the pre-and post-herbicidal activity of selected thiazolopyrimidine derivative
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