Risk assessment of the transfer of imazethapyr herbicide resistance from Clearfield rice to red rice
type: CreativeWork
description: Potential outcrossing between Clearfield rice and red rice will have a direct impact on the management and long-term usefulness of imazethapyr technology for rice weed control. The principal objective of this research was to determine the rate and agronomic consequences for outcrossing between Clearfield rice and red rice in south Louisiana. Collection and analysis of red rice samples across two years and 24 commercial locations indicated that red rice infestation after imazethapyr application differed substantially at different Clearfield locations. Straw hull and awnless red rice was the principal biotype observed for both years. Red rice populations possessed extensive variation for agronomic traits such as plant height, panicle length, tillers/plant, seeds/plant, seed set and grain weight. Outcrossing occurred from all Clearfield rice varieties (¡®CL121¡¯, ¡®CL141¡¯ and ¡®CL161¡¯) to red rice. An average outcrossing frequency of 0.163% was observed in red rice samples collected in 2002 with a range of 0.017% to 0.583%. A four-fold increase in outcrossing frequency of 0.679% was found in red rice samples collected in 2003 with two locations exhibiting outcrossing > 1%. Outcrossing frequency did not correlate with any agronomic trait from the red rice samples across two years. Imazethapyr resistance was generally controlled by a single dominant gene, except in some F2 populations where significant deviations from expected resistant/susceptible ratios were detected. Similar results were observed in F2 populations for segregation of pubescent/glabrous leaves. F1 hybrids between Clearfield rice and red rice in general did not show increased fitness in flowering characteristics over Clearfield rice, as most hybrids did not flower or produce seeds in the field. However, increased fitness in F1 hybrids, derived from red rice samples collected in 2002, was detected over Clearfield rice for plant height, tillers/plant, and panicles/plant. Enhanced fitness in F1 hybrids fr…
abstract: Potential outcrossing between Clearfield rice and red rice will have a direct impact on the management and long-term usefulness of imazethapyr technology for rice weed control. The principal objective of this research was to determine the rate and agronomic consequences for outcrossing between Clearfield rice and red rice in south Louisiana. Collection and analysis of red rice samples across two years and 24 commercial locations indicated that red rice infestation after imazethapyr application differed substantially at different Clearfield locations. Straw hull and awnless red rice was the principal biotype observed for both years. Red rice populations possessed extensive variation for agronomic traits such as plant height, panicle length, tillers/plant, seeds/plant, seed set and grain weight. Outcrossing occurred from all Clearfield rice varieties (¡®CL121¡¯, ¡®CL141¡¯ and ¡®CL161¡¯) to red rice. An average outcrossing frequency of 0.163% was observed in red rice samples collected in 2002 with a range of 0.017% to 0.583%. A four-fold increase in outcrossing frequency of 0.679% was found in red rice samples collected in 2003 with two locations exhibiting outcrossing > 1%. Outcrossing frequency did not correlate with any agronomic trait from the red rice samples across two years. Imazethapyr resistance was generally controlled by a single dominant gene, except in some F2 populations where significant deviations from expected resistant/susceptible ratios were detected. Similar results were observed in F2 populations for segregation of pubescent/glabrous leaves. F1 hybrids between Clearfield rice and red rice in general did not show increased fitness in flowering characteristics over Clearfield rice, as most hybrids did not flower or produce seeds in the field. However, increased fitness in F1 hybrids, derived from red rice samples collected in 2002, was detected over Clearfield rice for plant height, tillers/plant, and panicles/plant. Enhanced fitness in F1 hybrids fr…
author: Zhang, Weiqiang
keywords: simple sequence repeat markers, imazethapyr, red rice, outcrossing, Clearfield rice
date published: 2005-01-01T08:00:00Z
date modified: 2026-07-24T02:57:00Z
provider: Lousiana State University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Plant, Environmental Management and Soil Sciences

PropertyValue
property ID: DOI
value: 10.31390/gradschool_dissertations.83