Petunia Plants Transformed with an ABA Biosynthesis Gene under Control of a Stress-inducible Promoter Improve Water Use Efficiency under Limited Irrigation

Limited water availability and the long term effects of global warming makes drought resistant crops an attractive approach for geneticists and plant breeders. Previously, we reported that petunia plants transformed with a key abscisic acid (ABA) biosynthesis gene, 9-cis-epoxycarotenoid dioxygenase (NCED), using the stress inducible promoter rd29A resulted in mild increase in ABA accumulation, accompanied by stomatal closure and significant increase in drought resistance under drought stress. Here, we conducted a greenhouse study using the transgenic plants to evaluate the effect of three different irrigation regimes on plant growth, physiological parameters, relative water content, and water use efficiency. The irrigation treatments consisted of full irrigation-100% (I-₁₀₀) at field capacity, irrigation-75% (I-₇₅) and irrigation-50% (I-₅₀). The results showed that under well irrigated conditions (I-₁₀₀ treatment), P_rd29A::NCED plants exhibited a similar growth pattern and no significant differences were detected for all the physiological measurements when compared to the control plants. Under restrictive water supply (I-₇₅ and I-₅₀ treatments), transgenic plants overexpressing LeNCED maintained relatively higher water content, a higher gas exchange and higher photosynthetic activity, produced more biomass, and much better water use efficiency than the non-transformed control plants.