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- Author or Editor: Cecil Pounders x
A statistical model was used to partition the effects of age group, cutting position within the plant crown, and ramet environment on propagule development from stem cuttings collected from random stock plants of Ilex ×attenuata Ashe `Foster #2' (`Foster' holly). Most of the intra-clonal variation observed originated from sources not partitioned by the model. Small differences in growth were associated with sampling position within the crown. Repropagation gave no indication that factors measured by the model could be passed from ramet to propagule. Within-clone variation was not reduced by repropagation or by hedging propagules to force new growth.
Analysis of clonal variation for two rooting traits of western hemlock [Tsuga heteterophylla (Raf.) Sarg.] clones indicated that realized genetic gain would be improved by more effective partitioning and reduction of environmental differences associated with clones. Interactions between clones and multiple propagation dates were significant, but clone rank changes between dates were minor. Number of meted cuttings per plot (RC) and number of main roots per cutting (MR) were more highly correlated genetically (1.06) than phenotypically (0.36). Broad-sense heritabilitiesHx 2 = 0.62 and Hx 2 = 0.79 for RC and MR, respectively) and predicted genetic gain from clonal selection were moderately high. Both the percentage of rooted cuttings and root system quality could be rapidly improved by the clonal selection procedures used.
Crapemyrtles (Lagerstroemia) are deciduous shrubs or trees with prolific summer flowers. Their popularity is due in large part to low maintenance requirements in sunny climates, wide range of growth habits, disease resistance, and bark characteristics, as well as having a long flowering period (up to 120 days). Once well-established, they are extremely tolerant to heat and drought. Lagerstroemia was first introduced to the southern U.S. from southeast Asia more than 150 years ago, and is comprised of at least 80 known species. Most modern cultivars are L. indica and L. fauriei hybrids. L. speciosa is a tropical crapemyrtle with very large flowers, but lacks cold hardiness. It is a vigorous plant, but only when grown in Hardiness zones 9 or 10. We recently established microsatellite markers for Lagerstroemia and evaluated their utility for verifying interspecific hybrids. Here we verify F1 hybrids between L. indica `Tonto', `Red River', and L. speciosa. We also genotyped two commercially available L. speciosa hybrids. Currently, we are using crapemyrtle SSRs for cultivar identification and germplasm conservation. Future research includes marker-assisted breeding to produce powdery mildew and flea beetle resistant cultivars, as well as improved growth habit and fall foliage color.
Surviving extremes of climate is a fundamental component of horticultural production and research. The Southern Horticultural Laboratory has weathered many storms including Hurricane Camille and now Hurricane Katrina. The name of the research station has changed twice, both times following massive hurricanes. Before Hurricane Camille in 1969, the station title was the Tung Research Unit. After the devastation of the tung industry by Camille, the research focus changed to blueberries and other small fruit crops with a corresponding name change to Small Fruit Research Unit in 1976. The research objectives expanded to include ornamental research in 2001. Post Hurricane Katrina, the unit was renamed the Thad Cochran Southern Horticultural Laboratory to reflect the station's expanded research mission. This paper chronicles how the station reacted to the devastation of Hurricane Katrina. It also evaluates economic vitality of commodities researched at the station in contrast with storm effects on pecan and the demise of tung production. Katrina produced some temporary interruptions in production but no drastic restructuring of the type experienced with tung production after Camille is anticipated. Hurricanes are inevitable for the Gulf Coast region. Wise planning and implementation of preventative measures to protect horticultural crops and research will determine future success.
Crapemyrtle (L. indica and L. indica × L. fauriei hybrids) is one of the most popular flowering landscape plants in the U.S. Although many cultivars have been developed through breeding efforts, little has been published on the reproductive biology of the genus. The objective of this study was to evaluate barriers to successful self-seed production in crapemyrtle. Self-compatibility was assessed by comparing pollen tube growth, fruit and seed production, and seed germination following controlled self- and cross-pollinations. Observations of pollen tube growth at intervals up to 24 hours after self- and cross-pollination indicated no barriers to self-fertilization acting at the stigmatic or stylar level in L. indica, L. fauriei or cultivars derived from inter-specific hybrids of these two species. Self-pollinations of `Catawba', `Whit IV', `Tonto' and `Tuscarora' had lower percent seed pod set and seed germination than did cross-pollinations of these cultivars. The number of seeds per pod was lower when `Catawba', `Whit IV' and `Tuscarora' were self-rather than cross-pollinated, but no difference between `Tonto' self- and cross-pollinations was observed. When decreased pod set is combined with much lower seed germination for self-pollinations, selfing of crapemyrtle is extremely unproductive when compared to cross-pollination. A late-acting self-incompatibility system or inbreeding depression is indicated for L. indica and inter-specific crosses with L. fauriei.