The Effect of Co-occurring Heat and Water Stress on Reproductive Traits and Yield of Tomato (<i>Solanum lycopersicum</i>)

Abstract

Tomato (Solanum lycopersicum) productivity is negatively impacted by extreme weather events such as heatwaves, flooding and drought. This study evaluated the individual and additive effects of heat and water stress on reproductive traits and yield in the commercial tomato variety ‘Roma-VF’. Five weeks after sowing, five stress treatments were introduced consisting of combinations of heat and/or moderate and severe water stress. Heat-stressed plants were subjected to day/night temperatures of 35/23°C, and the control of 28/20°C. Moisture stress was imposed by natural depletion of soil water to 70% and 40% of field capacity (moderate and severe stress, respectively). After eight weeks of treatments, plants were placed under control conditions for a five-week recovery phase. Pollen morphology, number of flowers, fruits, and aerial biomass were recorded. Flowers from plants subjected to heat stress combined with either moderate or severe moisture stress did not produce any pollen during the treatment period. Further, by the end of the recovery period, 27–38% fewer fruits matured on plants subjected to either heat or moisture stress, while fruit production among plants subjected to both stresses simultaneously declined 90% relative to the control (P < 0.001). We conclude that the ‘Roma-VF’ tomato will be able to recover adequately from heatwaves provided plants are well irrigated. However, should heat and moisture stress co-occur, fruit yield is likely to be decimated and recovery is unlikely. This study is also the first report on additively combined effects of heat and water stress on the ‘Roma-VF’ tomato.