Search Results
Abstract
Six-month-old nonmycorrhizal or mycorrhizal [Glomus fasciculatum (Thaxter) Gerd. and Trappe] sour orange (Citrus aurantium L.) seedlings grown in a sandy soil amended with 0, 50, or 100 μg P/g soil were completely girdled 5 mm below the basal leaves. Eight weeks later, root exudates and extracts were analyzed and one-half of the nonmycorrhizal plants were inoculated with G. fasciculatum. Amounts of soluble sugars were greater in exudates from girdled nonmycorrhizal plants than in exudates from nongirdled or mycorrhizal plants. Girdling consistently reduced the amount of sugars in root extracts in all plants. Amounts of amino acids in exudates or extracts were not consistently affected by any treatment. Intensity of mycorrhizal infection was similar in girdled and nongirdled plants grown in sand without supplemental phosphorus, but mycorrhizal development was insignificant in plants inoculated after girdling and grown in sand amended with 50 or 100 μg P/g soil. Root infection was apparently dependent both on levels of photosynthates supplied to the roots and on the amount of nutrients in root exudates.
Abstract
Clonal multiplication of carnation (Dianthus caryophyllus L.) was accomplished in three stages: 1) shoot tip culture initiation stage, 2) shoot multiplication stage, and 3) rooting stage. The culture medium for the initiation stage was examined by comparing various inorganic salt mixtures, vitamin mixtures, carbohydrates, growth regulators, agars, pH’s, and additional supplements for their effect on growth and development of multiple shoots from shoot tips. When shoot tips (ca. 1 mm high) were grown on a modified Murashige and Skoog medium with 10 µM kinetin and 1 µM NAA, apical dominance was counteracted and morphologically normal shoots proliferated rapidly. Transferring these cultures after 4 wk to 100 ml flasks (one per flask) with 50 ml of same medium without agar and supplements, and with the kinetin concentration reduced to 2.5 µM, resulted in an average per original shoot tip of 28 shoots over 2 cm in height being produced in another 3 weeks. These shoots were rooted in BR-8 blocks or Jiffy-7 peat pellets under intermittent mist. Plantlets rooted in these supports were transferred easily to greenhouse conditions. Incorporation of carnation micropropagation into a pathogen-free propagative stock program should not be difficult, and might prove beneficial even if large scale use is limited by economic considerations.
Wild Anagallis monelli exhibits blue or orange flower colors in geographically isolated populations. A new red flower color was developed through breeding, and a three-gene model was proposed for the inheritance of flower color in this species. In this study, blue and orange wild diploid accessions were used as parents to develop six F2 populations (n = 19 to 64). Sexual compatibility between blue and orange wild individuals was low with only 29% of the hybridizations producing F1 individuals. Six of 14 cross combinations between F1 siblings produced fruits, and fruiting success ranged from 55% to 90%. The number of seeds per fruit averaged 14.1 and germination rates for the F2s were low (16.8% to 30.7%). In three of six F2 populations obtained, flower color segregation ratios for orange, blue, and red were not significantly different from the expected ratios under a previously proposed three-gene model. White flower color was obtained as a fourth color variant in two of the remaining F2 populations. For one of these populations, segregation ratios were not significantly different from expected ratios for an expanded four-gene model. White flowers did not contain anthocyanidins, suggesting that there was a mutation in the early stage of the anthocyanin pathway. Orange flower color was found to be primarily the result of pelargonidin, blue to malvidin, and red to delphinidin. These three pigments may be present simultaneously, and their ratios play a significant role in determining flower color. Other factors such as copigments, metal ions, or a different molecular conformation of the anthocyanin could also be involved in flower color determination.
Two crack-resistant and two crack-susceptible fresh-market tomato (Lycopersicon esculentum Mill.) cultivars were evaluated at varied soil moisture levels for physiological fruit defects and yield. Cultural practices recommended for staked-tomato production in North Carolina with raised beds, black polyethylene mulch, and drip irrigation were used. Soil moisture levels of less than −15.0, −30 to −40, and greater than −70 kPa were maintained and monitored using daily tensiometer readings. Soil moisture level had no effect on fruit cracking, blossom-end rot, zippers, or yield. However, there-were large differences among cultivars for fruit defects and total and marketable yields.
Abstract
A controlled environment technique using freshly silked, excised ears artificially infested with 1st instar larvae was developed for evaluating sweet com (Zea mays L.) for resistance to 2nd-brood European com borer, Ostrinia nubilalis (Hiibner). At 14 days, infested ears of the moderately resistant dent inbred ‘B52’ held in plastic bags at 27°C (day) 21° (night), high humidity, and 16 hour photoperiod (8.6 klx) had fewer 4th and 5th instar larvae and possibly lower larval weight Use of this technique could improve the efficiency of screening via artificial infestation by reducing environmentally caused variability.
Abstract
Minnesota 266 is an early maturing, andromonecious, short-internode breeding line of muskmelon, Cucumis melo L., from the vegetable improvement program of the Departments of Horticultural Science and Landscape Architecture, and Plant Pathology. It has value for the home garden and, in addition, it should be useful as a germplasm source for selection as well as for the development of commercial hybrids and/or types for mechanical harvesting.
Fresh-market tomato (Lycopersicon esculentum Mill.) was grown in a growth chamber, hydroponically, and in a field to evaluate the effect of foliar-applied boron (B) and root-applied K on growth, yield, quality, and tissue nutrient levels. Plant and root dry weight, plant height, fruit set, total yields, marketable yields, fruit shelf life, fruit firmness, and fruit crack were positively influenced by B treatments. Boron-treated plants contained more K than plants not treated with B. Plants not treated with B contained less calcium (Ca) than plants treated with B. Leaflets from plants treated with B maintained higher K levels during fruit development than leaflets from plants not treated with B. Roots from plants treated with foliar B had significantly more B than roots from plants not treated with B. Fruit from B-treated plants had significantly more B than fruit from plants not treated with B. This indicates B was translocated from leaves to root and fruit tissues.
Factors affecting the greenhouse propagation of firebush (Hamelia patens) by leafy stem cuttings during winter were studied. Without bottom heat (BH), mid-day rooting medium temperature was 22 ± 3 C. About half of the auxin-treated cuttings without BH rooted. Maintaining the rooting medium at 29-39 C increased rooting for auxin-treated cuttings to 96-100% and increased root length and visual rating scores several-fold. Rooting percentage, root length, and visual ratings were consistently high in perlite and low in peat. Stem-tip cuttings and sub-terminal stem segment cuttings with basal stem diameters of 3-5 mm rooted slightly better than stem segment cuttings with basal diameters of 6-8 mm. Stem-tip cuttings not treated with auxin but with BH had rooting percentages of 81-86%. Treatment of stem-tip cuttings with auxin generally yielded 90% rooting or above. Despite this, plants grown from auxin-treated cuttings were indistinguishable from plants grown from non-treated cuttings 2 months after the rooting period. Of the variables studied, BH had the most dramatic effect on rooting of firebush cuttings during winter months.
Seeds of Aquilegia chrysantha Gray were germinated under a variety of temperature regimes. Germination was nearly 90% under a day/night cycle of 25/20C, but was reduced to ≤ 40% under constant 25C or a 25/10C day/night cycle. With days between 25 and 29C (night = 20C), germination percentage dropped gradually to ≈ 60% with increasing temperature. With days >29C, germination declined dramatically such that no germination occurred at 31C. Neither kinetin (4.6 to 46 μm) nor ethephon (6.9 to 207 μm) was able to reverse the inhibitory effects of 33C days. Our results indicate that germination of A. chrysantha seed is sensitive to temperature and that germination ≈ 75% can be obtained under a 25 to 27C day/20C night regime. Chemical names used: 2-chloroethylphosphonic acid (ethephon); 6-furfurylaminopurine (kinetin).