In vitro growth and development of Alstroemeria `Cornell Pink' were evaluated on media containing different amounts of CaCl2, MgS O4, FeSO4, NO3, or NH4. Six levels of calcium chloride were originally examined (from 0 to 75 mM); the low levels proved to be most beneficial. Subsequent experiments used CaCl2 levels from 0 to 3.0 mM. Again, the low levels were most productive. Two experiments, with different gelling agents, were designed for MgSO4. The levels ranged from 0 to 15 mM. The 15 mM level produced explants with the greatest fresh weight. Three experiments were used to study the effect of FeSO4. The range was the same in all of the experiments (0 to 1 mM), but the increments and the gelling agents differed. In all three experiments, the 1 mM level proved to be toxic. The group with treatments from 0.01 to 0.5 mM had the best response over time. Both experiments with nitrogen found no response to different NO3:NH4 ratios. A positive linear response to rate was found within the range studied (20 to 80 mM).
The effects of Ca and N on cut flower production of Alstroemeria were determined in separate greenhouse experiments. Calcium was supplied as Ca(NO3)2 and CaCl2 at 0, 1, 2, 4, 8, and 12 mmol·L-1 added to tap water containing Ca at ≈0.2 mmol·L-1. Nitrogen was supplied as KNO3 and Ca(NO3)2 providing total N at 0, 3.5, 7, 14, 28.5, and 57 mmol·L-1 in tap water containing N <0.2 mmol·L-1. Nutrient solutions were applied at 7- or 10-day intervals to plants growing in a soilless medium in 2.6- or 5.5-L containers. Flowering stems were harvested when the primary florets opened. Total N concentration was measured in leaf tissue from the upper portion of flowering stems. Flower production was not affected by Ca supply, but increased with N supply to a maximum of about four stems per plant on a weekly basis at 28.5 mmol·L-1, then decreased to less than three stems per plant at 57 mmol·L-1. Nitrogen concentration in leaf tissue on a dry mass basis was maintained at 45 ±3 g·kg-1 in plants supplied with N at 28.5 mmol·L-1, 52±5 g·kg-1 at 57 mmol·L-1, but <40 g·kg-1 with N supply of 14 mmol·L-1 or lower. Nitrogen fertilization of Alstroemeria should be managed to maintain leaf tissue N close to 45 g·kg-1.
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.
Flowering dogwood (Cornus florida L.) is an important tree of forests and urban landscapes in the eastern United States. Amplified fragment length polymorphism (AFLP) markers were generated from genomic DNA of 17 cultivars and lines, and four duplicate samples of selective cultivars. Specific markers were identified for all except the following two lines and cultivar: MW94-67, MW95-12, and ‘Plena’. A dichotomous cultivar identification key was constructed based on AFLP data, and specific peaks or combinations of peaks were identified for all cultivars and lines. The key was assessed with seven anonymous (unlabeled) dogwood samples, and all unknowns except one were identified using the dichotomous key. Two of the unknown samples, ‘Cherokee Chief’ and ‘Cherokee Brave’, were difficult to distinguish using the AFLP markers. Intracultivar variation, up to 36% dissimilarity, was observed between duplicate samples of the same cultivar from different trees, suggesting that some mislabeling of trees had occurred at the nursery. The cultivar-specific AFLP markers can be used in breeding applications, patent protection, and in future projects, such as mapping the C. florida genome.
Despite an abundance of polyembryonic genotypes and the need for rootstocks that improve scion yield and productivity, simultaneous field testing of a wide range of mango (Mangifera indica L.) genotypes as rootstocks has not previously been reported. In this experiment, we examined the growth and yield of ‘Kensington Pride’ on 64 mango genotypes of diverse origin during the first four seasons of fruit production to identify those worth longer-term assessment. We also recorded morphological characteristics of seedlings of 46 of these genotypes in an attempt to relate these measures to subsequent field performance. Tree canopy development on the most vigorous rootstocks was almost double that on the least vigorous. Growth rates differed by more than 160%. Cumulative marketable yield ranged from 36 kg/tree for the lowest yielding rootstock to 181 kg/tree for the most productive. Yield efficiency also differed markedly among the 64 rootstocks with the best treatment being 3.5 times more efficient than the poorest treatment. No relationship was found between yield efficiency and tree size, suggesting it is possible to select highly efficient rootstocks of differing vigor. Two genotypes (‘Brodie’ and ‘MYP’) stood out as providing high yield efficiency with small tree size. A further two genotypes (‘B’ and ‘Watertank’) were identified as offering high yield efficiency and large tree size and should provide high early yields at traditional tree spacing. Efforts to relate the morphology of different genotype seedlings to subsequent performance as a rootstock showed that nursery performance of mango seedlings is no indication of their likely behavior as a rootstock. The economic cost of poor yields and low yield efficiencies during the early years of commercial orchard production provide a rationale for culling many of the rootstock treatments in this experiment and concentrating future assessment on the top ≈20% of the 64 treatments. Of these, ‘MYP’, ‘B’, ‘Watertank’, ‘Manzano’, and ‘Pancho’ currently show the most promise.