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Abstract
The pistillate flower of walnut is a complex structure (10, 13, 14) and is referred to as a pistil for simplicity. Pistils emerge terminally on shoot or spurs after different degrees of vegetative extension from mixed buds (9, 14). Such growth can range from essentially nil to about 1 m. Pistils are borne on a short peduncle (Fig. 1). Two pistils per peduncle are most common, but one or three, or (rarely) more, can occur. Flowers are wind-pollinated and all cultivars are considered to be cross- and self-fruitful (9, 14). Pistils become receptive very shortly after emergence from the shoot apex when the two stigma lobes begin to separate. Fertilization of ovules is necessary for nut development to maturity, but pollination and fertilization are not required for early growth of the ovary (14). Ovaries of nonpollinated flowers will enlarge at rates similar to those of fertilized ones for several weeks before abscising, when about 1 to 2 cm in diameter.
Several procedures for evaluating the resistance of tomato (Lycopersicon esculentum Mill.) to bacterial wilt were used to account for diversity in strains of Pseudomonas solanacearum Smith and to approximate resistance under field conditions. Five strains of P. solanacearum from Florida and one from North Carolina were inoculated onto 19 tomato genotypes and one tomatillo (Physalis ixocarpa Brot.) genotype using a stem-puncture technique. Genotypes were also transplanted as seedlings into naturally infested soil. Resistance was evaluated by comparing the response of each genotype to the susceptible cultivars Bonny Best and Sunny. With the stem-puncture technique, the mean incidence of disease ranged from 30% with the strain from North Carolina to 94% with a strain from northern Florida. Significant differences in the resistance of genotypes and pathogenicity of strains were observed. However, no interaction between strain and genotype was observed. Using naturally infested soil, the mean incidence of disease was 51% and significant differences in the resistance of genotypes were also observed. Hawaii 7997, Hawaii 7998, and CRA 66 had the lowest incidence of disease, regardless of inoculation method. The results indicate that assessing pathogen diversity and using a combination of resistance screening techniques can facilitate the evaluation of many genotypes, account for potential regional variability in the pathogen, and differentiate levels of field resistance to tomato bacterial wilt.
As triploid watermelons (Citrullus lanatus) increase in popularity, production has shifted away from seeded watermelons. To achieve successful fruit set in triploid watermelons, a diploid watermelon cultivar must be planted as a pollen source. Three diploid cultivars in 2005 and seven diploid cultivars in 2006 were evaluated at one and three locations, respectively, to determine their effectiveness as pollenizers. Each cultivar was planted within plots of the triploid watermelons ‘Tri-X 313’ (2005) and ‘Supercrisp’ (2006) with buffers on all sides of the plots to contain pollen flow within individual plots. Performance of pollenizers was based on triploid watermelon yield, soluble solids concentration, and incidence of hollowheart. In 2005, there were no significant differences in total weight, fruit per acre, average weight, or soluble solids concentration among pollenizers. In 2006, significant differences in yield were observed, and plots with ‘Sidekick’ as a pollenizer yielded the highest but were not significantly different from ‘Patron’, ‘SP-1’, ‘Jenny’, or ‘Mickylee’. In 2006, there were no significant differences in fruit per acre, soluble solids concentration, or incidence of hollowheart between pollenizers. The experimental design was successful in isolating pollenizers and there was minimal pollen flow outside of experimental plots as indicated by minimal fruit set in control plots.
`Solar Fire' is a heat-tolerant hybrid tomato (Solanum lycopersicum L. formerly Lycopersicon esculentum Mill.) with resistance to all three races of Fusarium wilt incited by Fusarium oxysporum f. sp. lycopersici Sacc. Snyder & Hansen. It has superior fruit-setting ability in comparison with most existing cultivars under high temperatures (>32 °C day/>21 °C night), and the fruit crack less under the rainy field conditions often present in the early fall Florida production season. Fla. 7776 is the pollen parent in `Solar Fire', providing much of the heat tolerance in this hybrid. It has large fruit-providing breeders with a parent to produce heat-tolerant hybrids with two heat-tolerant parents.
Abstract
‘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’.
Abstract
Ten fresh market tomato (Lycopersicon esculentum Mill.) genotypes were evaluated for yield stability in 7 environments within Florida. Genotype × environment interaction was significant for yield of marketable fruit. Linear relationships between mean yields of individual genotypes and environmental mean yields were evaluated to determine genotype stability. Mean square deviations from linear regression (s2d), regression coefficients (b1) and coefficient of linear determination (R 2) were used to evaluate phenotypic stability. ‘Sunny’, Castlehy 1035’, ‘Burgis’, ‘FTE 12’, and ‘Duke’ were considered stable and high yielding. An advanced breeding line, 827015-IBK, was considered stable but low yielding. ‘Hayslip’, D76127, ‘Flora-Dade’, and ‘Walter PF’ were considered unstable. This study suggests that yield stability differences occur among fresh market tomato genotypes. Therefore, selection of tomato genotypes for improved adaptability should be considered in tomato breeding programs.
Abstract
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.
To be useful for indicating plant water needs, any measure of plant stress should be closely related to some of the known short- and medium-term plant stress responses, such as stomatal closure and reduced rates of expansive growth. Midday stem water potential has proven to be a useful index of stress in a number of fruit tree species. Day-to-day fluctuations in stem water potential under well-irrigated conditions are well correlated with midday vapor-pressure deficit, and, hence, a nonstressed baseline can be predicted. Measuring stem water potential helped explain the results of a 3-year deficit irrigation study in mature prunes, which showed that deficit irrigation could have either positive or negative impacts on tree productivity, depending on soil conditions. Mild to moderate water stress was economically beneficial. In almond, stem water potential was closely related to overall tree growth as measured by increases in trunk cross-sectional area. In cherry, stem water potential was correlated with leaf stomatal conductance and rates of shoot growth, with shoot growth essentially stopping once stem water potential dropped to between −1.5 to −1.7 MPa. In pear, fruit size and other fruit quality attributes (soluble solids, color) were all closely associated with stem water potential. In many of these field studies, systematic tree-to-tree differences in water status were large enough to obscure irrigation treatment effects. Hence, in the absence of a plant-based measure of water stress, it may be difficult to determine whether the lack of an irrigation treatment effect indicates the lack of a physiological response to plant water status, or rather is due to treatment ineffectiveness in influencing plant water status. These data indicate that stem water potential can be used to quantify stress reliably and guide irrigation decisions on a site-specific basis.