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- Author or Editor: Wayne A. Mackay x
Micropropagation studies of several desirable species native to west Texas were initiated to develop clonal propagation systems for ornamental production. Actively growing shoots were collected from mature Texas Madrone and Mexican Redbud trees and successfully cultured on basal medium consisting of WPM salts, MS vitamins, 30g·l-1 sucrose, 0.8% Phytagar supplemented with 2.5 mg·l-1 BA. Shoots were subcultured every 4 weeks on the same medium to obtain sufficient culture material for experiments. Experiments were performed examining inorganic salt formulations, growth regulator materials, and gelling agents to optimize shoot proliferation and rooting.
Mature flowering Arbutus texana trees were successfully micropropagated from shoot tips. Optimum shoot proliferation was achieved on a basal medium consisting of WPM salts, MS vitamins, and sucrose supplemented with 11.1 or 22.2 μm BA and no auxin. Microcuttings rooted readily when pulsed with 6.1 μm IBA for 1 week and transferred to auxin-free medium. The addition of charcoal to the rooting medium improved root branching and elongation but suppressed root formation. Chemical names used: N-(phenylmethyl)-1H-purin-6-amine (BA); indole-3-butyric acid (IBA).
Seeds of Lupinus havardii Wats. and L. texensis Hook. were subjected to scarification, storage temperature (4 or 22 °C), and relative humidity (RH) treatments (11%, 23%, 52%, 75%, or 97% RH) for 12 months. Seed moisture increased as relative humidity increased with scarified seed having the greatest increase in seed moisture content regardless of storage temperature. For both species, the combination of seed scarification before storage, 75% RH, and 22 °C storage temperature resulted in a significant and rapid decline in germinability beginning at 4 months. Scarified L. texensis seed stored at 52% RH and 22 °C also exhibited a significant decline in germinability following 6 months storage. Seed of both species stored under all other conditions germinated similar to or higher than the initial germination rate after 12 months. These results clearly show that scarification can be performed before seed packaging as long as the seed packets are stored at ≤23% RH under 4 or 22 °C with no loss in germinability for at least 1 year.
Phlox paniculata `John Fanick' produces long lasting, dense terminal flower heads and has potential as a specialty cut flower. Quality and postharvest display life of cut flower heads depends primarily on ethylene-induced flower abscission, flower bud opening, and maintenance and development of flower color during vase life. Late events, such as flower and leaf senescence may also be detrimental to flower quality. In the control treatment, the initial red-pink and purple flower color changes to violet blue in 3 to 4 days, and may lose >50% of initial anthocyanins. Incorporating sucrose (SUC) in the vase solution not only maintained >75% of the initial floral pigments, but also promoted opening of additional flowers and anthocyanin development. Although both ethylene biosynthesis (AOA, ReTain, a.i. AVG) and action inhibitors (STS, 1-MCP) delayed flower abscission, STS and 1-MCP were relatively more effective than AOA and AVG. As in the control, newly opened flowers remained very small when treated with ethylene inhibitors, did not develop red-pink color, and exhibited only shades of violet blue color. Sucrose antagonized the effect of ethylene inhibitors. As such, the flowers in SUC+ethylene inhibitors treatments enlarged in size and developed a reddish-pink blue color. However, the flower quality in SUC alone was much superior than those in SUC+ethylene inhibitors. These results indicate that ethylene inhibitors, alone and in combination with SUC, were not of any additional value in improving postharvest performance and display life of cut phlox flower heads.
Seeds of four lupine species (L. microcarpus var. aureus, L. havardii, L. succulentis, and L. texensis) were subjected to 0, –2, –4, –6, or –8 bars osmotic potential using PEG 8000 solutions. Seeds of all species were acid scarified prior to placement in petri dishes containing the osmotic solutions. Petri dishes were placed in a seed germination chamber at 25°C with germination data collected daily for 15 days. Seeds of L. havardii, a desert species native to west Texas exhibited the greatest germination as osmotic potential declined while L. succulentis, a species adapted to moist sites, exhibited the greatest decline in germination as osmotic potential decreased. The other species exhibited intermediate germinability under the lower osmotic potentials.
Lupinus havardii and L. texensis are two commercially important species of lupines (bluebonnets) in Texas. There is no current information for the storage requirements of these two bluebonnet species seeds. A study was undertaken to examine the effects of relative humidity, temperature, and scarification on seed germinability. Seeds of the two bluebonnet species were stored under five relative humidity treatments (11%, 23%, 52%, 75%, and 95%) and two temperature treatments (3°C or 22°C) either scarified or nonscarified in factorial combination. Seed samples were removed monthly. Nonscarified seed were scarified and all seed were placed in a seed germination chamber and germinated in petri dishes containing moistened filter paper. All samples of seed stored under 95% relative humidity were lost to seed-borne contamination. Germinability of scarified seed of both species decreased within 5 months in the 22°C/75% RH treatment. Other treatments had no effect on germinability during 7 months of seed storage.
The Big Bend bluebonnet, Lupinus havardii Wats., is a showy winter annual native to a narrow geographical range in southwestern Texas with blue, fragrant 0.5–1.0-m-long racemes. The L. havardii raceme has considerable potential in the floral industry, because there is a need for high-quality, durable, raceme-type cut flowers. We began a research and breeding project in 1991 aimed at evaluating the potential for this species as a specialty cut flower. Breeding strategies included the development of selfed populations as well as random pollinations among selected individuals with the aim of improving flower color, uniformity, yield, and postharvest performance. Recurrent phenotypic selection has resulted in the development of blue, pink, and white color lines. Concurrently with the breeding efforts, research on seed germination, greenhouse culture for year-round production, postharvest handling, and shipping requirements have been conducted. Trials have indicated that L. havardii is adaptable to greenhouse culture and that individual plants can produce 15–25 marketable racemes within 4–5 months from sowing. Two years of commercial greenhouse trials have been completed. Blue and white cultivars will be released by Texas A&M Univ. within the next year.
Forty seedlings from each of 14 open-pollinated families of Taxodium distichum (L.) Rich. from the southeastern United States, central Texas, and south Texas/Mexico were evaluated in the summer of 2005 for foliar chlorosis in a field situation with alkaline soil. The families from Mexico and south Texas had the lowest levels of chlorosis followed by those from central Texas and then those from the gulf coast. Height growth and trunk diameter were inversely related to chlorosis levels. Open-pollinated families from the gulf coast also had a significantly lower foliar manganese content on an alkaline field site compared with the western families. When selecting plant material for an alkaline site, genotypes from Mexico and south Texas should be preferred followed by central Texas genotypes.
Studies examining exposure methods and callus type were conducted to develop an in vitro selection system using roridin E as a selection agent. Vacuum infiltration of callus with the toxin solution was the only successful selection method at the concentrations tested. Primary callus (callus originating directly from the explant) was not sensitive to roridin A or E at the concentrations used. Secondary callus (callus produced from primary callus) exhibited a differential response to roridins A and E similar to that of detached-leaf assays. Electrolyte leakage studies of callus were not conclusive in establishing the membrane as the site of toxin action or useful for screening tolerance in vitro. A small percentage of callus from tolerant and susceptible cultivars survived repeated exposure to roridin E at 50 μg·ml-1.