Date of Award

Summer 6-13-2023

Degree Type

Thesis

Degree Name

Master of Science in Integrative Biology (MSIB)

Department

Biology

Committee Chair/First Advisor

Mario Bretfeld

Major Professor

Dr. Mario Bretfeld

Second Committee Member

Chris Cornelison

Third Committee Member

Hendrick Den-Bakker

Fourth Committee Member

Daniel Ferreira

Abstract

Salinity stress has been shown to improve hydroponic produce quality such as that of tomato but at the trade-off of produce yield. In order to improve demand for hydroponic produce, techniques that improve salinity tolerance could offset declines in yield without altering the improved quality of produce. In two separate trials, we tested whether foliar inoculation of the ACC deaminase-producing bacteria Methylobacterium oryzae CBMB20 improved salt tolerance in tomatoes grown in a semi-hydroponic system using an indeterminate variety exposed to 26mM NaCl (Trial 1) and a determinate variety exposed to 17mM NaCl (Trial 2). We also tested how salinity and inoculation with M. oryzae impacted chlorophyll fluorescence, leaf-gas exchange parameters, and tomato Brix levels. Salinity did not alter per unit chlorophyll fluorescence parameters, net carbon assimilation, or fruit Brix levels but did decrease stomatal conductance and fruit yield. In Trial 1, inoculation with M. oryzae did not improve yield-related parameters or net carbon assimilation but increased Fv’/Fm’, decreased NPQt and stomatal conductance, and increased instantaneous water-use efficiency (WUE). In Trial 2, inoculation reduced plant biomass and decreased qL but increased Fv’/Fm’, decreased NPQt, and did not significantly alter fruit yield. Responses in leaf gas exchange and photochemistry to inoculation possibly indicate hormonal changes induced by M. oryzae, which has previously shown to alter tomato ethylene and auxin levels, and these effects are likely cultivar-variable.

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