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- Author or Editor: A.D. Bryan x
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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.
The genus Aronia Medik., also known as chokeberry, is a group of deciduous shrubs in the Rosaceae family, subtribe Pyrinae. The four commonly accepted species include A. arbutifolia (L.) Pers., red chokeberry; A. melanocarpa (Michx.) Elliott, black chokeberry; A. prunifolia (Marshall) Reheder, purple chokeberry; and A. mitschurinii (A.K. Skvortsov & Maitul). Wild and domesticated Aronia species are found as diploids, triploids, and tetraploids. Genetic improvement of polyploid Aronia genotypes has been limited by suspected apomixis, which may be widespread or distinct to tetraploids. The objectives of this study were to elucidate the reproductive mechanisms of Aronia species and reveal the occurrence of apomixis within the genus and along ploidy lines. Twenty-nine Aronia accessions [five A. melanocarpa (2×), five A. melanocarpa (4×), eight A. prunifolia (3×), four A. prunifolia (4×), six A. arbutifolia (4×), and one A. mitschurinii (4×)] were used in this study. Intra-accession variability was evaluated by growing out progeny from each open-pollinated maternal accession and comparing plant phenotypes, ploidy levels, and amplified fragment length polymorphism (AFLP) marker profiles between the progeny and maternal accession. Progeny of diploid and tetraploid maternal plants had ploidy levels identical to maternal plants, except for UC009 (A. melanocarpa, 2×) which produced a mix of diploids and tetraploids. UC143 and UC149 (A. prunifolia, 3×) produced all triploid offspring, whereas all other triploid accessions produced offspring with variable ploidy levels including 2×, 3×, 4×, and 5×. Pentaploid Aronia has not been previously reported. Diploid accessions produced significant AFLP genetic variation (0.68–0.78 Jaccard’s similarity coefficient) in progeny, which is indicative of sexual reproduction. Seedlings from tetraploid accessions had very little AFLP genetic variation (0.93–0.98 Jaccard’s similarity coefficient) in comparison with their maternal accession. The very limited genetic variation suggests the occurrence of limited diplosporous apomixis with one round of meiotic division in tetraploid progeny. Triploid accessions appear to reproduce sexually or apomictically, or both, depending on the individual. These results support our understanding of Aronia reproductive mechanisms and will help guide future breeding efforts of polyploid Aronia species.
Planting depth during container production may influence plant growth, establishment, and subsequent landscape value. A lack of knowledge about the effects of common transplanting practices may lead to suboptimal performance of planted landscape trees. Planting depth, i.e., location of the root collar relative to soil grade, is of particular concern for posttransplant tree growth both when transplanted to larger containers during production and after transplanting into the landscape. It is unknown whether negative effects of poor planting practices are compounded during the production phases and affect subsequent landscape establishment. This study investigated effects of planting depth during two successive phases of container production (10.8 L and 36.6 L) and eventual landscape establishment using lacebark elm (Ulmus parvifolia Jacq.). Tree growth was greater when planted at grade during the initial container (10.8 L) production phase and was reduced when planted 5 cm below grade. In the second container production phase (36.6 L), trees planted above grade had reduced growth compared with trees planted at grade or below grade. For landscape establishment, transplanting at grade to slightly below or above grade produced trees with greater height on average when compared with planting below grade or substantially above grade, whereas there was no effect on trunk diameter. Correlations between initial growth and final growth in the field suggested that substantial deviations of the original root to shoot transition from at-grade planting was more of a factor in initial establishment of lacebark elm than the up-canning practices associated with planting depth during container production.
`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.
Tree transplanting practices influence plant survival, establishment, and subsequent landscape value. However, transplanting practices vary substantially within the horticultural industry. Of particular importance is the location of the root collar relative to soil grade at transplant. The objective of this study was to determine the effects of factorial combinations of planting depths, root collar at grade or 7.6 cm either above or below grade, and soil amendments on container-grown (11 L) Quercus virginiana Mill. Soil treatments included a tilled native soil (heavy clay loam, Zack Series, Zack-urban land complex, fine, montmorillonitic, thermic, udic paleustalfs), native soils amended with 7.6 cm of coarse blasting sand or peat that were then tilled to a depth of 23 cm, or raised beds containing 20 cm of sandy loam soil (Silawa fine sandy loam, siliceous, thermic, ultic haplustalfs). A significant (P ≤ 0.05) block by soil amendment interaction occurred for photosynthetic activity. Incorporation of peat significantly decreased the bulk density of the native soil. Planting depth had no significant effect on photosynthetic activity or stem xylem water potential at 3 months after transplant. Soil water potentials did not statistically differ among treatments.
Abstract
Florida 1011, an inbred line of tomato (Lycopersicon esculentum Mill.) was developed at the Agricultural Research and Education Center in Homestead and Bradenton in cooperation with the H. J. Heinz Company. The line is designated Florida 1011 in recognition of its Southern Tomato Exchange Program (STEP) designation (3).