An Ethylene Blocker Delays Epidermal Cell Death At the Location of Adventitious Root Emergence in ‘Beauregard' but Not in ‘Evangeline' Sweetpotato Cuttings

In sweetpotatoes, the emergence of adventitious root primordia represents a critical phase in plant establishment and determination of potential storage root yield. Experiments with ‘Beauregard’ and ‘Evangeline’ sweetpotato cuttings revealed differential response to 1-MCP application. ‘Evangeline' cuttings rooted regardless of 1-MCP treatment. In contrast, ‘Beauregard’ cuttings treated with 1-MCP showed significantly reduced adventitious root emergence and development relative to the untreated controls. Trypan blue staining of nodal tissue that failed to show emerged adventitious root primordia showed localized dead tissue in the general area where adventitious roots emerge. The degree of staining appeared to correspond with the stage of adventitious root emergence, with the staining becoming more intense around the time an adventitious root primordium eventually emerges through a crack in the epidermis. This response correspond with reported results of ethephon-induced adventitious root emergence in rice nodes. These results suggest that ‘Beauregard’ and ‘Evangeline’ cuttings differ in the ability to sense the presence of ethylene. This represents the first evidence of genotype-specific ethylene involvement in adventitious rooting in sweetpotato cuttings.