【Objective】Development of transgenic drought tolerant varieties of maize is an effective way to solve the production problems such as drought disaster and water shortage. The objective of this study was to identify and analyze the effects LOS5 on drought tolerance of maize which were transferred with Arabidopsis thaliana LOS5 gene. And, the transgenic LOS5 maize lines with strongest drought tolerance were screened out for the maize breeding. 【Method】 Under the gradient stress of 150, 225, 300, 375, 450 and 600 mm (CK) irrigation amount, the yield and drought tolerance of eight LOS5 transgenic maize lines and their receptor Zheng58 were identified in field. Yield components and other agronomic traits were measured and compared for determining what were the characters most correlated with the enhanced drought tolerance. The transgenic maize lines with significant drought tolerance were screened out for the transgenic breeding application.【Result】The yields and drought tolerances of all 9 maize lines decreased gradually with the decreasing of irrigation amount from 600 to 150 mm. The yields of 8 transgenic maize lines were all significantly higher than that of the receptor Zheng58 in the stress range of 225 mm to 450 mm, and the maximum difference was in the half irrigation (300 mm) of the normal irrigation (600 mm). In the irrigation amount of 300 mm, the drought resistant coefficients of 8 transgenic lines were 0.56 to 0.70, which were significantly higher than that of the receptor Zheng58(0.5), and the drought tolerance then increased by 12% to 40%. The materials in descending order of the drought resistant coefficient were T8920B6, T8920B2, T8920B7, T8920B5, T8920B1, T8920B4, T89B3, B8920B8 and the receptor Zheng58. In the respect of vegetative development, only the leaf color SPAD value of transgenic lines (38.4 to 42.4) were significantly higher than that of the receptor Zheng58 (28.7 to 37.5) in the irrigation of 150 to 225 mm, but the biomass above the ground, plant height and ear site height had no significance among the 9 maize lines. In the development of ear, the ear weight and the ear length of 8 transgenic lines were 42.3 to 61.6 g and 10.9 to 13.1 cm, which were significantly higher than 36.4 to 40.7 g and 8.5 to 11.8 cm of the receptor, respectively, in the irrigation treatments of 150 to 225 mm, but the cob weight and ear diameter were not with significance among the transgenic lines and their receptor. In the grain development, the grain numbers per ear and the grain number per row of the 8 transgenic lines were 86.6 to 182.6 and 8.4 to 15.6, which were significantly higher than 57.3 to 83.2 and 4.9 to 7.1 of the receptor, respectively, but no significant difference was found among the 8 transgenic maize lines and their receptor in the respect of grain rows per ear and 100-grains weight.【Conclusion】LOS5 had little effect on the vegetable growth of transgenic maize before flowering, but it played a positive role in maintaining of ear length, grain number per row and leaf color of late-filling stage after flowering. And, the ear weight, grain number per ear and yield of transgenic maize were therefore maintained at higher levels when stressed. Drought tolerance of LOS5 transgenic lines was enhanced with different degrees, so field identification and screening is necessary. Stress with a half of normal irrigation can maximize the difference of maize drought tolerance, and was satisfactory for the identification and screening.
