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- Author or Editor: K. Peter Pauls x
The chilling tolerance of commercial Lycopersicon esculentum cultivars (H2653, H722), Solanum lycopersicoides, an F1 hybrid of S. lycopersicoides × Sub-Arctic Maxi, and 25 BC2F2 lines of L. hirsutum × H722 (backcrossed twice to H722) was evaluated using a chlorophyll fluorescence assay. The ratio of the initial to the peak fluorescence (Fo: Fp) measured from fully expanded leaves was chosen as an indicator of plant health. Chilling induced an increase in Fo: Fp that was correlated with the sensitivity of the plant to low-temperature stress. Values of Fo: Fp remained low for cold-treated S. lycopersicoides and the F1 hybrid, which showed few symptoms of chilling-related damage, whereas the commercial cultivars, which were essentially intolerant to low temperatures, had large increases in Fo: Fp. A full range of Fo: Fp values was measured in the 25 BC2F2 lines, indicating that some chilling tolerance from the L. hirsutum parent was expressed by plants in these populations.
‘Horizon’, a small shoot-mass tomato (Lycopersicon esculentum Mill) cultivar, and ‘Sunny’, a large shoot-mass cultivar were planted at 30.5-, 61-, and 91-cm within-row spacings at five locations in Florida during Spring 1985 to determine if yields differed between these cultivars and among plant densities. Marketable weight and number of fruit per plant, mean fruit size (g/fruit), and shoot weight increased linearly with an increase in within-row spacing. Marketable weight of fruit/ha decreased linearly with wider within-row spacings. Responses of both cultivars to within-row spacing were similar for each measured trait, except for marketable fruit number per plant. A larger increase in marketable number of fruit per plant occurred between 61- and 91-cm within-row spacings for ‘Sunny’ than for ‘Horizon’. Fruit : shoot ratio (w/w) was not influenced by within-row spacings or cultivars. Each measure variable differed among locations. These results suggest that ‘Sunny’, with a larger inherent shoot growth, sufficiently compensated for smaller shoot growth when grown at higher plant densities to maintain marketable fruit yields comparable to ‘Horizon’.
Ten fresh-market tomato (Lycopersicon esculentum Mill.) genotypes were evaluated for stability of fruit firmness, citric acid, soluble solids, β-carotene and ascorbic acid concentrations, sugar : acid ratio, color, N content, and dry weight when grown in nine environments. Linear relationships between the genotype means for a given trait and the mean for the trait in each environment were used as an indicator of stability. A stable genotype for a given trait was considered to possess a regression coefficient (b1) ⩽ a coefficient of linear determination (r2) > 0.50, a genotype mean above the grand mean (mean of all genotypes), and a nonsignificant deviation from regression mean square (S2d). Using these criteria, stability in the nine environments was shown by the fruits of the various cultivars as follows: ‘Flora-Dade’, ‘FTE-12’, and D76I27 for firmness; ‘Castlehy 1035’ and ‘Sunny’ for citric acid; ‘Walter’ for soluble solids concentration; ‘FTE-12’ for ascorbic acid concentration; ‘Hayslip’, ‘Walter’, and ‘Burgis’ for sugar : acid ratio; ‘FTE-12’ and ‘Hayslip’ for β-carotene concentration: ‘Flora-Dade’ and 827115-IBK for color a/b; ‘Castlehy 1035’ and ‘Hayslip’ for dry weight; and ‘Walter’ for N content. Stable genotypes are less sensitive to environmental changes and are more adapted to favorable and unfavorable conditions than unstable genotypes. No genotype was found to be stable for every fruit quality trait in the nine environments. Stability of fruit quality characteristics should be considered in tomato breeding programs to develop genotypes adapted to diverse environmental and management conditions.