Ethylene resistance in flowering ornamental plants – improvements and future perspectives

Various strategies of plant breeding have been attempted in order to improve the ethylene resistance of flowering ornamental plants. These approaches span from conventional techniques such as simple cross-pollination to new breeding techniques which modify the plants genetically such as precise genome-editing. The main strategies target the ethylene pathway directly;others focus on changing the ethylene pathway indirectly via pathways that are known to be antagonistic to the ethylene pathway, e.g. increasing cytokinin levels. Many of the known elements of the ethylene pathway have been addressed experimentally with the aim of modulating the overall response of the plant to ethylene. Elements of the ethylene pathway that appear particularly promising in this respect include ethylene receptors as ETR1, and transcription factors such as EIN3. Both direct and indirect approaches seem to be successful, nevertheless, although genetic transformation using recombinant DNA has the ability to save much time in the breeding process, they are not readily used by breeders yet. This is primarily due to legislative issues, economic issues, difficulties of implementing this technology in some ornamental plants, as well as how these techniques are publically perceived, particularly in Europe. Recently, newer and more precise genome-editing techniques have become available and they are already being implemented in some crops. New breeding techniques may help change the current situation and pave the way toward a legal and public acceptance if products of these technologies are indistinguishable from plants obtained by conventional techniques.

ABA-mediated regulation of leaf and root hydraulic conductance in tomato grown at elevated CO2 is associated with altered gene expression of aquaporins

Elevated CO_(2)concentration in the air(e[CO_(2)])decreases stomatal density(SD)and stomatal conductance(gs)where abscisic acid(ABA)may play a role,yet the underlying mechanism remains largely elusive.We investigated the effects of e[CO_(2)](800 ppm)on leaf gas exchange and water relations of two tomato(Solanum lycopersicum)genotypes,Ailsa Craig(WT)and its ABA-deficient mutant(flacca).Compared to plants grown at ambient CO_(2)(400 ppm),e[CO_(2)]stimulated photosynthetic rate in both genotypes,while depressed the gs only in WT.SD showed a similar response to e[CO_(2)]as gs,although the change was not significant.e[CO_(2)]increased leaf and xylem ABA concentrations and xylem sap pH,where the increases were larger in WT than in flacca.Although leaf water potential was unaffected by CO_(2)growth environment,e[CO_(2)]lowered osmotic potential,hence tended to increase turgor pressure particularly for WT.e[CO_(2)]reduced hydraulic conductance of leaf and root in WT but not in flacca,which was associated with downregulation of gene expression of aquaporins.It is concluded that ABA-mediated regulation of gs,SD,and gene expression of aquaporins coordinates the whole-plant hydraulics of tomato grown at different CO_(2)environments.