Author(s): Thang Xuan Nguyen and Mariam Sticklen
Drought and salt are two major abiotic stress factors resulting in maize seed and biomass yield losses. In an attempt to produce drought and salt tolerant maize plants, rapidly growing embryogenic calli were produced in vitro from maize immature embryos, and bombarded with a gene construct containing the barley HVA1 (Hordeum vulgaris abundant protein) and the Liberty herbicide resistance (bar) genes using the BiolisticTM device (gene gun). The bombarded calli were chemically selected in a regeneration medium containing 2.5 mg/L of glufosinate ammonium (the active ingredient of Liberty herbicide), 1 mg/L of benzyl amino purine (BAP). Plantlets were produced four weeks after calli were transferred into the regeneration medium and incubated under fluorescent light condition of 16 hr light/8 hr dark at 25°C in a growth room. The polymerase chain reaction (PCR) and Southern blot hybridization confirmed the integration, and the reverse transcription PCR (RT-PCR) and Northern blotting confirmed the transcription of the HVA1 transgene, and herbicide treatment confirmed the expression of the bar transgene in upto the fourth generations (T3) of mature plants. The T3 plants that transcribed the HVA1 showed higher leaf relative water content (RWC), higher leaf and root biomass, and survived complete drought for 15 days while the wild-type non-transgenic control plants died. The T3 plants were also tolerant to 100-300 mM NaCl (especially to 200 mM) while the wild-type control non-transgenic plants showed severe damage under these salt treatments. The research presented here might serve as getting one step closer to developing a drought and salt tolerant maize.
