Physiological traits associated with high temperature tolerance differ by fruit types and sizes in tomato (Solanum lycopersicum L.)

Abstract

Plants are very sensitive to environmental stresses, particularly to high temperature (HT) which is predicted to increase. This study was conducted to investigate the response to HT for identifying physiological traits associated with HT tolerance in tomato. Thirty-eight tomato accessions with three fruit sizes (cherry, medium and large) were grown in greenhouses where temperature set-point for ventilation was 25 °C and 40 °C for normal temperature (NT) and HT, respectively. HT increases plant height and stem diameter but little effect on leaf length and width. For reproductive traits, HT has positive effect on the number of flowers (NFL) but negative on the number of fruits (NFR), fruit set (FS), weight (FW) and yield (FY), and pollen germination (PG) and tube length. In the correlation analysis, except for accession T37 with extreme value causing spurious results, PG did not show significant correlation with FS, FW and FY, but with NFL and NFR in HT condition. NFR (HT), FS (HT) and FY (NT) are identified as physiological traits associated with HT tolerance based on correlation with FY (HT). However, their association to HT tolerance differ by fruit sizes. NFR (HT) was significantly correlated with FY (HT) in sub-population of cherry (r = 0.859**, n = 14), medium (r = 0.848**, n = 7) and large fruit types (r = 0.769**, n = 16) but not in total population (r = 0.302NS, n = 37). FS (HT) and, interestingly, FY (NT) were significantly correlated with fruit yield (HT) in total population and a cherry fruit sub-population but not in medium and large fruit sub-population. Results suggest that physiological traits associated with HT tolerance differ by fruit size and breeding programs should consider different selection criteria for different fruit types when develop cultivars with HT tolerance.