Physiological Responses of Drought Stressed Creeping Bentgrass Transgenic for an Ipt Gene Controlling Cytokinin Synthesis.

Drought stress is a widespread abiotic plant disease that causes a decline in plant health and vigor.  Creeping bentgrass (Agrostis stolonifera L.)  is a turfgrass species that has only moderate drought tolerance and its quality as a functional turf declines rapidly due to drought.  Many physiological changes occur due to a reduction in plant water status including a loss of leaf relative water content, photochemical efficiency (FvFm), chlorophyll content, hormone content, and root mass. This study evaluated such physiological parameters affected by drought in creeping bentgrass transformed with a bacterial gene (ipt) encoding the enzyme adenine isopentenyl phosphotransferase ligated to two stress- activated promoters, senescence activated promoter Sag12 and heat shock promoter HSP18. Northern confirmed transgenic lines showed the ability to maintain significantly higher levels of FvFm, chlorophyll content, shoot and root cytokinin and abscisic acid content, and root mass relative to the control line, which was transformed with an empty vector. Results may indicate that increased levels of cytokinins during drought stress may be beneficial for overall plant viability and function to delay drought induced leaf damage and senescence.