Symptoms of foliar chlorosis or bleaching, interveinal chlorosis of lower leaves, leaf edge and tip necrosis, stunted growth and delayed flowering of Eustoma increased as pH decreased below 6.5 in various peat-vermiculite based media for all cultivars tested. Symptoms were evident with or without microelement amendments in the media or fertilizer. A 5×5 factorial with pH of media and fertilizer solutions ranging from 5.1 to 7.5 indicated fertilizer pH did not negate plant response to low media pH. Leaf tissue levels of Zn were elevated at low media pH and negatively correlated to plant growth and flowering characteristics, while imbalances in tissue levels of N, P, K, Ca, Mg, Fe, Mn, Cu and B appeared to be less important. Symptomatic plants grown in media with a pH from 5.0 to 5.8 had tissue levels of Zn ranging from 200 to 1200 ppm, and plants without symptoms in media with a higher pH had leaf tissue levels from 40 to 100 ppm Zn.
Brent K. Harbaugh
Maurus V. Brown, James N. Moore, Ronald W. McNew and Patrick Fenn
A study was conducted to determine how resistance to downy mildew [Plasmopara viticola (Bert. & Curt.) Berl. & de Toni] is inherited in germplasm (Vitis vinifera L., V. labrusca L., V. rupestris Scheele, and V. riparia Michx.) used for breeding table grapes. Crosses, including reciprocals, among parents possessing different levels of downy mildew resistance were evaluated in 1994 and 1995. The proportion of foliar tissue with sporulation, chlorosis, or necrosis was used to measure resistance. All genotypes were rated for these characters on two separate dates in 1994 and 1995. Hypersensitive flecking was also evaluated in the 1995 seedlings to determine its relationship with downy mildew resistance. Crosses with at least one resistant parent had a larger number of resistant offspring than crosses between two susceptible parents. General combining ability (GCA) effects were highly significant for 1994 and 1995. Specific combining ability effects were significant, but were relatively small compared to GCA, suggesting additive gene action was a primary influence on downy mildew resistance. Heritability estimates for sporulation, chlorosis, and necrosis were the highest at the second rating in 1994 (0.88, 0.74, and 0.57, respectively) and 1995 (0.50, 0.60, and 0.60, respectively). Reciprocal crosses indicated that maternal inheritance did not influence downy mildew resistance. A small percentage of progeny with hypersensitive flecking were identified from the germplasm. Seedlings with the flecking characteristic tended to have lower sporulation, chlorosis, and necrosis ratings earlier in the growing season.
Allan M. Armitage, Natalia K. Hamill and Stephanie L. Anderson
As part of the New Floriculture Crop Program at the University of Georgia, a research project was initiated in Fall 2004 to determine the suitability of woody shrubs for forcing in the greenhouse. This paper will provide an overview of the research, indicating plants that were determined to be suitable for greenhouse forcing and sales in the retail area and those that were discarded from the program. About 15 taxa were initially selected for the program based on habit, foliar qualities, and flowering (if present). All plants were subjected to 1.7 °C to 4.4 °C for 0, 6, or 10 weeks in a controlled temperature cooler. Based on growth and visual characteristics, Leptodermis oblonga, Indigofera pseudotinctoria `Rose Carpet', Forsythia × intermedia `Golden Peep', and Philadelphus coronaria `Manteau d'Hermaine' were discarded. Caryopteris × clandonensis `Sunshine Blue', Leycesteria formosa `Golden Lanterns', Sambucus nigra `Black Lace', Philadelphus coronaria `Variegata', and Physocarpus oblongifolius `Summer Wine' were investigated further. Data presented for Physocarpus suggested that cooling was not necessary for growth; however, 10 weeks of cooling resulted in the least time to finish in the greenhouse. Zero, 6, and 10 weeks cold resulted in 17, 10, and 7 weeks finish time, respectively. Additional work on Kolkwitzia, Buddleia, and Wegelia conducted in 2005 and future research will be discussed.
James L. Gibson and Brian E. Whipker
Twenty-six ornamental cabbage and kale (Brassica oleracea var. acephala L.) cultivars were transplanted into 20.8-cm (8-inch) pots in Fall 1998 to classify their foliage traits and determine their response to the plant growth regulator (PGR) daminozide. Daminozide foliar sprays were applied at 0, 2500, or 5000 mg·L–1 (ppm) 3 weeks after potting. Two cultivars treated with 2500 mg.L-1 and eight cultivars treated with 5000 mg·L–1 were significantly smaller in height when compared to the nontreated plants. Using the Range/lsd formula, the vigor of the cultivars was classified by height. Foliage characteristics were described and cultivars of ornamental cabbage, notched ornamental kale, and curly ornamental kale were selected based on the shortest number of days until a significant center color change and the largest center color diameter. In Fall 1999, recommended cultivars selected in 1998 were treated with daminozide at 5000 mg·L–1 or uniconazole at 5 mg·L–1 14 days after potting, plus a nontreated control. All cultivars responded similarly to the PGRs with greater control being observed with daminozide with a smaller plant height of 13% as compared to 6% for uniconazole. For effective height control, PGR applications to ornamental cabbage and kale should be applied 2 weeks after potting.
Ted E. Bilderback and Mary R. Lorscheider
Packaged commercial grower mixes routinely contain wetting agents. Studies report that dry components such as pine bark can be more thoroughly moistened if wetting agents are used. Under frequent leaching irrigations, wetting agents have been reported to enhance nutrient loss. Effective longevity is expected to be only 3 to 4 weeks. New products claim greater longevity and advertise that less water volume is required for optimum plant growth. One such product is Saturaid (Debco Pty, Victoria, Australia). The objective of this study was to evaluate the effect of Saturaid on physical properties, nutrient levels, and growth under decreasing irrigation volume. The granular wetting agent was incorporated at 0, 1.0, and 2.0 g·liter–1 substrate volume. Cotoneaster dammeri `Skogholm' plants were potted into 2.8-liter pots and irrigated with 500 ml of water for 22 days, after which one-third of the containers received 425 ml (–15%) and one-third were irrigated with 350 ml (–30%) daily. Saturaid had little effect on moisture and air characteristics, and no effect on foliar nutrients or on leachates collected at 43, 64, or 84 days. When irrigation volume was decreased 15%, top dry weight was greatest at 2 g, followed by 1 g of Saturaid. When irrigation volume was decreased 30%, the same results occurred for top and root growth.
D.A. Raymond, C. Chong and R.P. Voroney
Four containerized deciduous ornamental shrubs, [silverleaf dogwood (Cornus alba L. `Argenteo-marginata'), red-osier dogwood (Comus sericea L.), ninebark (Physocarpus opulifolius L.), and deutzia (Deutzia gracilis L.)] were grown in 12 composts containing (by volume) spent mushroom substrate (50%), waxed corrugated cardboard (WCC; 0%, 25%, or 50%), and/or pulverized wood wastes (PWW; 50%, 25%, and 0%). Supplemental N as poultry manure and/or soybean wastes was added to some composts. Growth (shoot dry weight, average of two seasons) of all species was better or similar in most composts compared with two controls (100% pine bark and 80% pine bark: 15% peat: 5% sand). Deutzia grew best in 50% WCC composts and other species in 25% WCC composts. Porosity characteristics of the composts were acceptable for container growing (50% to 60% total; 25% to 30% aeration). Total soluble salts were initially high and potentially phytotoxic, particularly in the 50% WCC composts but were quickly leached and resulted in no injury to plants. There were no symptoms of nutrient deficiencies or toxicities in any of the species tested. Foliar nutrient (N, I P, K, Ca, Mg, Mn, Zn, and Fe) concentrations in all species were within normal ranges, except for low Mn and Fe concentrations in red-osier dogwood during the second season.
Patrick M. McCool and Robert C. Musselman
Almond (Prunus amygdalus Batsch cv. Nonpareil), apricot (Prunus armeniaca L. cv. Royal Blenheim), and peach [Prunus persica (L.) Batsch cv. Halford] grafted nursery stock seedlings were exposed once per week for 4 hours to a maximum O3 concentration of 0.25 μl·liter-1 in field exposure chambers. Exposures were repeated for a total of 4 months in 1986 (year 1) and 1987 (year 2). Trunk caliper, number of shoots, and net growth (total seasonal weight increase) were measured at the end of each year. Almonds appeared to be the most sensitive to O3. Almond seedlings exhibited extensive foliar injury from O3, while apricot and peach seedlings were relatively insensitive. Total net growth of O3-exposed almond was reduced during both years relative to the controls and an impact on caliper was evident after year 2. Apricot seedlings exposed to O3 developed a thinner trunk but more shoots than the controls in both years. Peach tree seedlings exposed to O3 had fewer shoots than the controls at the conclusion of year 2 but thicker trunks after both years. No significant difference in variance or shape of distribution of net growth within the treatment populations between O3-exposed seedlings and controls was detected for any of the three fruit crops. The impact of O3 on young, nonbearing perennial fruit crops may be most evident in specific growth characteristics, such as net growth or trunk caliper.
D.C. Elfving, E.C. Lougheed and R.A. Cline
A midsummer foliar daminozide (DZ) application (750 mg a.i./liter) to `Macspur McIntosh'/M.7 apple trees (Malus domestics Borkh.) reduced preharvest drop and retarded flesh firmness loss and starch hydrolysis when tested at harvest; DZ also reduced fruit ethylene production at harvest and after 19 weeks of storage at 0.5C. Root pruning at full bloom (May) resulted in increased soluble solids concentration (SSC) and firmer flesh and less starch hydrolysis at harvest, but not consistently each year. Full-bloom root pruning reduced the incidence of stem-cavity browning and brown core, but again not each year. Full-bloom root pruning did not influence ethylene evolution at harvest but did reduce post-storage ethylene evolution in two of three seasons. Full-bloom root pruning generally was less effective than DZ in altering fruit behavior, while root pruning later than full bloom had virtually no effect. Trunk scoring or ringing increased SSC and retarded loss of flesh firmness before harvest and following storage, but had little effect on starch hydrolysis. Scoring or ringing decreased incidence of some disorders and reduced post-storage ethylene evolution, although these treatments had little effect on ethylene production at harvest. Trunk scoring influenced some fruit characteristics more strongly than DZ. Fruit size was not affected by any treatment in any year. Chemical name used: butanedioic acid mono (2,2 -dimethylhydrazide) (daminozide).
Ryan N. Contreras, Ron Determann and Mara Friddle
There is a great deal of variation among japanese-cedar cultivars with regard to growth form, foliar characteristics, and winter browning. Differences in winter browning have been observed and documented by a number of authors. Previous research has established that there are differences in winter foliage color between cultivars included in the current study; however, no quantitative analysis under standardized conditions was conducted. Because of a previous report that tetraploid forms of japanese-cedar remain green during winter as a result of increased antioxidant enzyme activity, we hypothesized that cultivars that exhibit reduced winter browning were polyploids. We screened 56 accessions of japanese-cedar using flow cytometry analysis of 4′,6-diamidino-2-phenylindole (DAPI)-stained nuclei and performed chromosome counts on three cultivars. All accessions were diploid (2n = 2x = 22), although there were significant differences in genome sizes among the cultivars. Holoploid genome sizes ranged from 18.9 pg for var. sinensis JCRA to 22.3 pg for ‘Viridis’ with a mean of 20.1 pg. Chromosome counts for cultivars Ogon, Oye Keme, and Viridis supported the flow cytometry results. Although the underlying cause of the variability in morphology and winter browning among cultivars is unclear, our results show that differences in ploidy level are not responsible, because all tested genotypes were diploid. Chemical name: 4′,6-diamidino-2-phenylindole (DAPI).
J.H.M. Barten, J.W. Scott and R.G. Gardner
Pointed blossom-end morphology may be used to reduce blossom-end scar size in large-fruited, fresh-market tomatoes (Lycopersicon esculentum Mill.). The usefulness of this characteristic has been limited due to persistence of pointedness on mature fruit, resulting in postharvest bruising, and to close association of pointedness with leaf curl, which may increase foliar disease problems. The inheritance of pointedness in three breeding lines (NC 140, Fla 890559-24, and Fla 894413-1) and four accessions with previously described blossom-end morphology genes [LA 2-5 with persistent style (pst), LA 986 with beaky (bk), LA 1787 with beaky-2 (Bk-2), and LA 2353 with nipple tip (n)] was investigated. In F1 s and F2s of crosses with wild types, some pointedness was observed in heterozygotes, but the level of expression was generally close to wild type expression, except for LA 986. Consequently, Bk-2 in LA 1787 was renamed bk-2. F1 complementation tests were difficult to interpret. Wild types segregated in F2s of all complementation crosses, except for LA 986 × LA 2-5, a result indicating the presence of the same gene in these two accessions. Three new nipple-tip genes were named; n-2 in NC 140, n-3 in Fla 890559-24, and n-4 in Fla 894413-1. None of the seven accessions tested had significant leaf curl. Early identification of mutant plants by the shape of the stylar base in flowers at anthesis was reliable only for bk. Various blossom-end morphology genes may be backcrossed into otherwise desirable breeding lines, and complementing parents may be intercrossed to obtain optimal smoothness in the hybrid without undesirable pointed mature hybrid fruit.