Report on resistance of Portulaca oleracea to glyphosate application

Abstract

During 2008, a confined field experiment was conducted on “Evaluation of glyphosate resistant Bt maize hybrids”. In this experiment, 900, 1800 and 3600 g ae of glyphosate was tried for standardizing the dose of glyphosate for glyphosate resistant Bt corn hybrids. We have observed that Portulaca oleracea was not killed with all the doses of glyphosate application and was reported earlier. To confirm this, a mini field experiment has been conducted during 2014 to study that is there any resistant mechanism with Portulaca oleracea against glyphosate. Portulaca oleracea seeds have been collected and sown in 12 microplots with a dimension of 1m x 1m and allowed to grow. Glyphosate has been applied with sub optimal (5ml/litre), optimal (10ml/litre), and higher dose (15 ml/litre) along with ammonium sulphate (2%) as an adjuvant. Drying symptom with glyphosate application at 10 ml and 15 ml was observed on 3 DAHS whereas no drying symptom was observed in Potulaca oleracea weeds which were applied with glyphosate at 5 ml/litre and this might be due to sub – optimal dose of glyphosate application. In glyphosate application of 10 ml and 15 ml/litre; Leaf alone showed drying symptom and the stem remains healthy pink and also glyphosate has not been translocated to the root portion of the Portulaca oleracea as it showed healthy root system. Rainfall was received on 5DAHS; by utilizing the moisture; regeneration was observed in glyphosate applied plots. This showed that moisture would facilitate for the regeneration or regrowth of the Portulaca oleracea and might be happened due to the poor translocation of the herbicides. There was no complete control of Portulaca with optimal and high dose of glyphosate application on 10 DAHS. Hence, after 30 DAHS a weed count was taken and it was showed that only 30% population was controlled with sub – optimal dose of glyphosate application (5ml/litre); 49% and 60% control with glyphosate application at recommended (10ml/litre) and 15ml/litre respectively.