Authors: Elena R Sanchez Olguin Griselda ArrietaEspinoza Jorge A Lobo Ana M EspinozaEsquivel
Publish Date: 2009/03/29
Volume: 18, Issue: 4, Pages: 633-647
Abstract
Herbicideresistant rice cultivars allow selective weed control A glufosinate indica rice has been developed locally However there is concern about weedy rice becoming herbicide resistant through gene flow Therefore assessment of gene flow from indica rice cultivars to weedy rice is crucial in Tropical America A field trial mimicking crop–weed growing patterns was established to assess the rate of hybridization between a Costa Rican glufosinateresistant rice line PPTR and 58 weedy rice accessions belonging to six weedy rice morphotypes The effects of overlapping anthesis morphotype weedy accession/PPTR percentage and the particular weedy accession on hybridization rates were evaluated Weedy rice accessions with short overlapping anthesis 4–9 days had lower average hybridization rates 01 than long anthesis overlapping 10–14 days accessions 03 Hybridization also varied according to weedy rice morphotype and accession Sativalike morphotypes WM020 WM120 hybridized more readily than intermediate WM023 WM073 WM121 and rufipogonlike WM329 morphotypes No hybrids were identified in 11 of the 58 accessions analyzed 21 accessions had hybridization rates from 001 to 009 21 had rates from 01 to 09 and 5 had frequencies from 1 to 23 Another field trial was established to compare the weedy ricePPTR F1 hybrids with their parental lines under noncompetitive conditions F1 hybrids had a greater phenotypic variation They had positive heterosis for vegetative trait and reproductive potential number of spikelets and panicle length traits but negative heterosis for seed set This study demonstrated the complexity of factors affecting hybridization rates in Tropical America and suggested that the phenotype of F1 hybrids facilitate their identification in the rice fieldsThe authors wish to thank B Valverde J Gressel and C MallorySmith for valuable comments on the manuscript and Fabio Blanco for statistical advice This work was part of the project “Gene flow analysis for assessing the safety of bioengineered crops in the tropics” no 997860200100 convened by CIAT Cali Colombia and financed by BMZ and GTZ Germany Also this research has also been financed by the Rockefeller Foundation and the Foundation for Cooperation Costa RicaUnited States of America CR USA
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