RIMSULFURON UPTAKE, TRANSLOCATION, METABOLISM AND ALS SENSITIVITY TO RIMSULFURON IN TWO MAIZE HYBRIDS

Cilia L.  Fuentes; Gilles D.  Leroux

RIMSULFURON UPTAKE, TRANSLOCATION, METABOLISM AND ALS SENSITIVITY TO RIMSULFURON IN TWO MAIZE HYBRIDS

Autores

Cilia L. Fuentes

Gilles D. Leroux

Editor

Universidad Nacional de Colombia

Descripción

Research was conducted to determine the role in selectivity of uptake, translocation, metabolism and ALS (acetolactate synthase) activity of rimsulfuron in two maize (Zea maysL.) hybrids ('Cargill 2127', tolerant, and 'Pioneer 3897', sensitive) grown at temperatures of 14°C and 21°C. Fortyeight hours after treatment (HAT), uptake of rimsulfuron was 40% and 67% in 'Pioneer 3897', and 26% and 43% in 'Cargill 2127' at 14°C and 21°C, respectively. Neither total translocation nor allocation of rimsulfuron in variousorgans differed greatly between the hybrids. Translocation of 14C-rimsulfuron was greater at 21°C (53%) than at 14°C (23%), 48 HAT. In 'Pioneer 3897' over 65% and 30% ofthe total 14C-activity present in plant extracts was recovered as the parent compound within 24 HAT, at 14°C and21°C, respectively. However, in 'Cargill 2127' detoxification of rimsulfuron was not affected by temperature, and27% of the 14C-total activity was recovered as the parent compound. Crude ALS extracts from 'Pioneer 3897' and 'Cargill 2127' maize seedlings were treated with various doses (0.001, 0.005, 0.01, 0.1 and 1.0 uM) of rimsulfuron. Based on ALS specific activity, I50 values differed sligthlybetween the two hybrids (I50 'Pioneer 3897' = 0.091 uM and I50 'Cargill 2127' = 0.142 uM). These results suggestthat the mechanism of rimsulfuron tolerance in maize could be mainly explained by differential herbicide uptake and detoxification, with translocation and ALS sensitivity having little effect on differential tolerance of these maize hybrids to rimsulfuron. On the other hand, the greater uptake and translocation of rimsulfuron at 21°C, compared to 14°C, could explain the observed herbicide injury in maize at high temperatures under field conditions.