Development, field evaluation, and agronomic performance of transgenic herbicide resistant rice

Abstract

The commerical cultivars ‘Gulfmont’, ‘IR72’ and ‘Koshihikari’ were genetically engineered using electric discharge particle bombardment to express the bar gene which confers resistance to the broad-range herbicide glufosinate. Southern and northern blot analyses of transgenics material revealed stable integration and expression of introduced transgenes in the lines evaluated. In a few plants, silencing of the uidA marker gene was detected at the transcriptional level. Field studies were conducted in 1993 and 1994 at the Rice Research Station near Crowley, LA. This report summarizes results from the first two years of field trial for transgenic Gulfmont and Koshihikari. Transgenic cultivar IR72 was tested in 1995 and preliminary results are similar to those reported for transgenic Gulfmont. All 11 independently derived transgenic lines produced fertile, normal looking seed at maturity. Significant differences were observed in the absence of the herbicide between parental cultivars and transgenic Gulfmont-and Koshihikari-derived lines for days to 50% heading (20% of transgenic lines), plant height (13%), and grain yield (7%). Foliar application of glufosinate had little or no effect on agronomic performance of all transgenic Gulfmont and IR72 lines, while herbicide applications affected grain, yield and plant height of some transgenic Koshhikari. Non-transgenic plants of all three cultivars at the 4-leaf stage were killed within 7 days after 1.12 or 2.24 kg/ha glufosinate applications. Significant differences among certain transgenic lines were observed for agronomic traits after herbicide applications. These results demonstrate that the bar gene was effective in conferring field-level resistance to glufosinate in rice. Variation among transgenic lines required traditional breeding selection procedures to identify superior agronomic types with high levels of herbicide resistance and showed the necessity to generate several independent transgenic lines of each cultivar.