Evaluation Of Transgenic Rice Line 99-1 In Tolerance To Glufosinate And Its Competition Against Barnyardgrass

Glufosinate-tolerant transgenic rice line 99-1 newly bred in China was studied in growth characters, tolerance to glufosinate, effects of the environmental factors (nitrogen fertilizer and light intensity) on tolerant stability, detecting methods, and competitiveness against barnyardgrass (Echinochloa crus-galli) from 2001 to 2003.The germination capacity of transgenic line 99-1 was lower than that of non-transgenic cultivars Yuefu and Zhongzuo 93. However, there were no significant differences among them in germination rate, established seedling rate when direct-seeded or transplanted.The non-effect concentration of glufosinate was 8.28 mg/L and 48.97 mg/L for seeds and 2-leaf seedlings of the transgenic line, respectively; 1.83 mg/L and 2.06 mg/L for seeds and 2-leaf seedlings of non-transgenic cultivars, respectively. These non-effect levels were much lower than that of the residue of glufosinate when applied at the recommended dosages. So the residue of glufosinate had no effect on the transgenic and non-transgenic rice cultivars.The transgenic rice line 99-1 had good tolerance to glufosinate. However, there was difference in tolerance among different growth stages. Direct-seeded plants at the 2-leaf stage tolerated to the herbicide only at 0.5 kg a.i./hm2. Some seedlings could die when the herbicide of 1.0 kg a.i./ hm2 was applied at this stage. Transplanted plants of the line were more tolerant than direct-seeded plants. Even though the plant height and tillering were affected, grain yield of the line was not reduced when glufosinate of 1.0 kg a.i./ hm2 was applied at the 2-leaf stage. However, some transplanted seedlings died and grain yield was reduced when glufosinate of 2.0 kg a.i./ hm2 at this stage. The plants at 4- to 8-leaf stages became more tolerant and there was no grain yield reduction even glufosinate was applied at 2.0 kg a.i / hm2.High light intensity could increase herbicidal effect of glufosinate on transgenic rice line 99-1. Even though there were no significant differences in plant height and fresh weight of the line between the two treatments of low and high light intensities, the chloroplast content, the promoter amount ofbar gene, and the expressed protein from the gene of the treatment of high light intensity were significantly reduced under high light intensity when glufosinate was applied. All nitrogen fertilizers urea, potassium nitric acid, and ammonium sulfate used in this study could have the plants of transgenic line 99-1 recovered from injury resulted from glufosinate application. However, the speed of the recovery varied with nitrogen fertilizer. The injured plants recovered faster when urea or potassium nitric acid was applied than when ammonium sulfate applied.Detecting methods of the transgenic rice plants were compared in this dissertation. Shoot length was a better parameter than root length when seed bioassay was done. Concentration of glufosinate used in seed bioassay could be from 10 mg/L to 100 mg/L. Using either primer pair 5--ACCATCGTCAACCACTACATCG-3' and 5'-GCTGCCAGAAACCCACGTCAT-3' or 5'-ACCATCGTCAACCACTACATCG-3' and 5'- GAGGTCGTCCGTCCACTCCTG-3' could amplify specific segment of bar gene cloned in the transgenic plants. Using primer pair 5'-GCTCCTACAAATGCCATCA-3' and 5'- GATAGTGGGATTGTGCGTCA-3' could amplify specific segment of promoter CaMV35S cloned in the transgenic plants. Specific protein band expressed by bar gene could also be utilized to identify the transgenic plants from non-transgenic plants. The seed bioassay method is simple, rapid, and economical, but needs live seeds. PCR-based method is precise and reliable and needs little samples, but it is labor-intensive, relatively time-consuming, and cost-expensive.A replacement experiment was conducted in a greenhouse to compare the competitiveness of transgenic rice line 99-1 and non-transgenic rice cultivar Yuefu against barnyardgrass. The result showed that there was difference in competitiveness between them. Based on aggressivity parameters, the non-transgenic cultivar Yuefu was...