A 2-year greenhouse study was conducted at Clemson University, Clemson, S.C., in 2003 and 2004 to determine drought responses of six bermudagrass (Cynodon spp.) cultivars at four irrigation intervals. Cultivars selected from the 2002 National Turfgrass Evaluation Program Bermudagrass Trial were `SWI-1012', `Arizona Common', `Tift No.3', `Tifsport', `Aussie Green', and `Celebration'. Treatments included 5-, 10-, and 15-day irrigation intervals plus a control (irrigated daily). Volumetric soil water content (VSWC) and evapotranspiration (ET) rates were recorded every 3 days. Turfgrass quality (TQ) was observed weekly and root weight was measured at the end of a 6-week study. `Aussie Green' and `Celebration' produced the highest TQ rating (>7) at week 4 when watered daily. After 4 weeks of the 5-day irrigation interval, all cultivars showed unacceptable quality ratings (<7). However, `Aussie Green' and `Celebration' were able to maintain an acceptable TQ rating (7), compared to `Arizona Common' (5.1) and `Tift No.3' (5.8) at week 2 (5-day treatment). `Celebration' produced 114% and 97% greater root weight than `Tifsport' and `Aussie Green', respectively, when pooled across all irrigation treatments. At the 15-day irrigation interval treatment, six bermudagrass cultivars pooled together produced 78%, 22%, and 11% greater root weight vs. control, 5-day, and 10-day treatments, respectively. When pooled for all treatments, `Aussie Green' and `Celebration' VSWC was 5% and 7% lower than `Tift No.3', and ET rates were 26% and 30% greater than `Arizona Common'. Based on these results, irrigating bermudagrass in 5-day intervals should be carefully monitored.
C.M. Baldwin, H. Liu, L.B. McCarty, W.L. Bauerle, and J.E. Toler
R.L. Jarret, S. Kresovich, T. Holms, Janelle Evans, and Z. Liu
Simple sequence repeats (SSRs) were isolated from a size-fractionated genomic DNA library of watermelon (Citrullus lanatus L. cv. New Hampshire Midget). Screening of the library with five oligonucleotide probes, including (GT)11, (AT)11, (CT)11, (GC)11, and (TAA)8, detected the occurrence of 96 positive colonies among ≈8000 recombinants. Automated DNA sequencing revealed the presence of SSRs. PCR primer pairs homologous to the regions flanking the SSR loci were synthesized commercially and used to screen 56 watermelon genotypes for the occurrence of SSR polymorphisms. Amplification products were separated using nondenaturing PAGE. Eighty percent of the primer pairs produced amplification products of the expected size and detected polymorphisms among the genotypes examined. The use of SSRs for watermelon germplasm characterization is discussed.
Lusheng Zeng, Jiayang Liu, Robert N. Carrow, Paul L. Raymer, and Qingguo Huang
Organic coatings on sand particles can cause soil water repellency (SWR) where a soil does not spontaneously wet; this leads to challenges in water management and crop production. In laboratory studies, we evaluated a novel approach using direct application of 10 enzymes at three (low, medium, high) dosages to remediate SWR on two sand turfgrass soils in a 3-day incubation study and a second study at high dosage with 1-day incubation. A soil:solution ratio of 1:1 (10 g soil and 10 mL solution) was used and a deionized water control included. For Soil 7, a very strongly hydrophobic soil from a localized dry spot turfgrass area with a water drop penetration time (WDPT) of 7440 seconds (untreated) and 332 to 338 seconds (water-treated), the high dosage rates of laccase, chitinase, and protease at 1 and 3 days incubation resulted in WDPT of less than 60 seconds (i.e., hydrophilic soil). Pectinase exhibited similar results only in the 3-day incubation study. On the strongly hydrophobic Soil 21 (WDPT of 655 seconds untreated; 94 to 133 water-treated) from the dry area of a fairy ring-affected area on a turfgrass site, high dosages of chitinase, laccase, pectinase, and protease reduced WDPT to less than 60 seconds in both studies; and medium dosage rates were also effective for all but protease in the 3-day incubation study. Each of the four most effective enzymes for reducing WDPT, noted previously, demonstrated a significant exponential or logarithmic relationship between decreasing WDPT and increasing enzyme dosage. Further studies in field situations will be required to determine enzyme effectiveness on SWR and water management.
Angela R. Davis, Charles L. Webber III, Wenge Liu, Penelope Perkins-Veazie, Amnon Levi, and Stephen King
High-quality, high-phytonutrient watermelons [Citrullus lanatus (Thumb.), Matsum & Nakai] have strong market opportunities. To produce highly nutritious fruit in a seedless triploid market, the nature of phytonutrient accumulation as affected by ploidy must be understood. The present study performed on six field-grown watermelon diploid (2n) inbred lines, their induced autotetraploids (4n), and autotriploids (3n) determined the importance of ploidy on quality and nutritional content. Lycopene, total soluble solids (TSS), L-citrulline (hereafter referred to as citrulline), glutathione (GSH), weight, width, and length were measured in ripe fruit from one location. Our findings contradict some previous manuscripts, which did not use diploid inbred lines and their induced autoploidy relatives. Of the traits we analyzed that did not have a family-by-ploidy interaction (citrulline, GSH, weight, and width), we determined citrulline levels were not significantly affected by ploidy in five of six families nor was there a significant correlation when all family’s citrulline values were averaged. Previous studies on field-grown fruit that did not use autoploidy lines suggested triploid fruit had more citrulline than diploid fruit. GSH was higher in autotriploid than in diploid or autotetraploid (95.0 vs. 66.9 or 66.7 μg·g−1 GSH, respectively). Additionally, we found an association with higher GSH in larger fruit. Autotriploid fruit were, in general, heavier and wider than diploid and autotetraploid fruit, and autotetraploid fruit were generally smaller than diploid fruit. Of the traits we analyzed that had a family by ploidy interaction (lycopene, TSS, and length), we determined within four families, ploidy affected lycopene concentration, but whether this interaction is positive or negative was family-dependent. These data suggest the triploid state alone does not give fruit higher lycopene concentrations. The mean TSS was higher in autotetraploid than in autotriploid, which was again higher than in diploid fruit averaged across families (10.5%, 10.2%, and 9.5% TSS, respectively); there was a family × ploidy interaction so the significance of this increase is affected by the triploid’s parents. Lycopene and TSS had a slight positive correlation. Four of six families showed no statistical correlation between ploidy and length, and although mean length across family demonstrated smaller tetraploid fruit, the family-by-ploidy interaction demonstrates that this observation is family-dependent. Length and width correlate well with weight when combining data for all ploidy levels and when analyzing each ploidy separately. Length correlates more closely with width in autotriploid fruit than in diploid or autotetraploid fruit.
Christian M. Baldwin, Haibo Liu, Lambert B. McCarty, William L. Bauerle, and Joe E. Toler
Studies on bermudagrasses (Cynodon spp.) have demonstrated variability in salinity response among species and cultivars. However, information on ultradwarf bermudagrass cultivars in relative salinity tolerance associated with trinexapac-ethyl (TE) [4-(cyclopropyl-α-hydroxy-methylene)-3,5-dioxocyclohexanecarboxylic acid ethyl ester], a cyclohexanedione type II plant growth regulator (PGR), remains unknown. Therefore, two replicated greenhouse studies were conducted to determine the salinity tolerance of two ultradwarf bermudagrass cultivars treated with TE on turfgrass quality (TQ), total root biomass, and root and shoot tissue nutrient concentration. Turfgrasses included `TifEagle' and `Champion' bermudagrass (Cynodondactylon(L.) Pers. × C. transvaalensisBurtt-Davy). Daily sodium chloride (NaCl) exposure was 0, 12.90 (8,000 ppm), 25.80 (16,000 ppm), and 38.71 dS·m–1 (24,000 ppm). Biweekly TE applications (active ingredient 0.02 kg·ha–1) were initiated 2 weeks after salinity exposure. `Champion' was more salt-tolerant than `TifEagle' based on TQ and root mass. At 12.90, 25.80, and 38.71 dS·m–1 of NaCl, nontreated (without TE) `Champion' consistently outperformed nontreated `TifEagle' with greater TQ on most rating dates. At 12.90 dS·m–1, TE treated `Champion' (8.0) had greater TQ than nontreated `TifEagle' (6.1) at week 10. Regardless of TE application, after 2 weeks of applying 25.80 dS·m–1 of NaCl, both cultivars fell below acceptable TQ (<7). When averaged across all salinity treatments, applying TE four times at 0.02 kg·a.i./ha in two week intervals enhanced root growth for both bermudagrass cultivars by 25%. Also, both cultivars decreased root mass as salinity levels increased. Non TE-treated `TifEagle' had 56% and 40% less root and shoot Na uptake compared to TE treated cultivars at 25.80 dS·m–1. In conclusion, the two bermudagrass cultivars responded differently when exposed to moderate levels of NaCl.
Q. Liu, S. Salih, J. Ingersoll, R. Meng, L. Owens, and F. Hammerschlag
Transgenic `Royal Gala' apple (Malus × domestica Borkh.) shoots were obtained by Agrobacterium-mediated gene transfer using the plasmid binary vector pGV-osm-AC with a T-DNA encoding a chimeric gene consisting of a secretory sequence from barley-amylase joined to the modified cecropin MB39 coding sequence. Shoots were placed under the control of a wound-inducible, osmotin promoter from tobacco. The integration of the cecropin MB39 gene into apple was confirmed by Southern blot analysis. The transformation efficiency was 1.5% when internodes from etiolated shoots were used as explants and 2% when leaf explants were used. Both non- and transgenic tetraploid plants were produced by treatment of leaf explants with colchicine at 25 mg·L-1, and polyploidy was confirmed by flow cytometry. Of the diploid transgenics, three of seven were significantly more resistant to Erwinia amylovora than the non-transgenic `Royal Gala' control. Also, in one instance, a tetraploid transgenic was significantly more resistant than the diploid shoot from which it was derived.
Wayne Brown, Theo J. Blom, George C.L. Chu, Wei Tang Liu, and Lisa Skog
The sensitivity of easter lilies (Lilium longiflorum) to either ethylene or methane (products of incomplete burning in gas-fired unit heaters) was tested during rooting [3 weeks at 18 °C (65 °F)], vernalization [6 weeks at 6 °C (43 °F)] and subsequent greenhouse forcing (15 weeks at 18 °C). Starting at planting, easter lilies were exposed for one of seven consecutive 3-week periods (short-term), or for 0, 3, 6, 9, 12, 15, 18, or 21 weeks starting at planting (long-term) to either ethylene or methane at an average concentration of 2.4 and 2.5 μL·L-1(ppm), respectively. Short- or long-term exposure to ethylene during rooting and vernalization had no effect on the number of buds, leaves, or plant height but increased the number of days to flower. Short-term exposure within 6 weeks after vernalization reduced the number of buds by 1 bud/plant compared to the control (no ethylene exposure). However, extensive bud abortion occurred when plants were exposed to ethylene during the flower development phase. Long-term exposure to ethylene from planting until after the flower initiation period resulted in only two to three buds being initiated, while continued long-term exposure until flowering caused all flower buds to abort. Short-term exposure to methane at any time had no effect on leaf yellowing, bud number, bud abortion, or height and had only a marginal effect on production time. Long-term exposure to methane from planting until the end of vernalization increased both the number of buds, leaves and height without affecting forcing time, leaf yellowing or bud abortion.
C. Stevens, L. P. Pusey, V.A. Khan, J.Y. Lu, C.L. Wilson, M.A. Wilson, M.K. Kabwe, J. Liu, E. Chaultz, and S. Droby
Flavorcrest, Camden. C. L. Wilson, Loring, Elberta, Summergold and Harken peach varieties were inoculated and naturally infected with Monilinia fructicolo after ultraviolet light irradiation (W-C 254nm) showed increased resistance to brown rot disease. Although dosages ranged from 0 to 20 KJ/m2. 7.5 KJ/m2 was considered the most effective for the peach varieties tested. Pretreatment of peaches by field spraying or dipping into a benomyl fungicide showed no significant differences between non-treated and UV-C treated peaches. However. a combination of a low dose of benomyl (.15g/L) 3 days following UV-C treatment showed a synergistic effect on brown rot reduction when compared to Peaches treated with UV-C alone and a greater reduction of brow rot than benomyl control.
J. Liu, C. Stevens, V.A. Khan, J.Y. Lu, C.L. Wilson, O. Adeyeye, M.K. Kabwe, L. Pusey, E. Chalutz, T. Sultana, and S. Droby
The application of low hormetic low-dose ultraviolet light (WV-C, 254 nm) on fruits and vegetables to stimulate beneficial responses is a new method for controlling storage rots and extending the shelf-life of fruits and vegetables. The present study was aimed at treating tomatoes (lycopersicon esculentum) with different UV-C dosages (1.3 to 40 KJ/m2) to induce resistance to black mold (Alternaria alternata), gray mold (Boytris cinerea), and Rhizopus soft rot (Rhizopus stolonifer). Thesediseases were effectively reduced when tomatoes were artificially inoculated following UV-C irradiation UV-C treated tomatoes were firmer in texture and less red in color than the control tomatoes, indicating a delay in ripening. Slower ripening and resistsace to storage rots of tomatoes are probably related. The positive effect of UVC on tomatoes decreased as treatments were performed at stages of increased ripeness.