The development of calyxes in ‘Korla’ fragrant pear is influenced by hormones. This study was conducted to investigate the effects of different plant growth regulators on the endogenous hormone content of young ‘Korla’ fragrant pear fruit. The hormone contents [indoleacetic acid (IAA), gibberellin acid (GA3), and abscisic acid (ABA)] of young ‘Korla’ pear fruits treated with water, IAA, and triiodobenzoic acid (TIBA) were determined by high-performance liquid chromatography, and the relationship between the content and ratio of endogenous hormones and calyx abscission in ‘Korla’ fragrant pear was explored. The results showed that the rate of calyx abscission in the ‘Korla’ pear fruits treated with TIBA was significantly higher than that of fruits treated with water and IAA, and that of fruits treated with water was significantly higher than that of fruits treated with IAA. The GA3 content was higher than the IAA and ABA contents during each period. The IAA content of the stalk was higher than that of the calyx tube and flesh. The GA3 and ABA contents of the calyx tube were higher than those of the stalk and flesh. The IAA and GA3 contents of the first order were higher than those of the fourth order. The ABA content of the fourth-order fruit was higher than that of the first order. The (IAA+GA3)/ABA in the calyx tube was significantly higher than that in the flesh and fruit stalk. After IAA treatment, the IAA, GA3, and ABA contents of the first-order calyx tube increased by 47.7%, 17%, and 31.6%, respectively, whereas those of the fourth-order calyx tube increased by 65.3%, 39.9%, and 33.2%, respectively. After TIBA treatment, the IAA, GA3, and ABA contents of the first-order calyx tube increased by 46.1%, 36.5%, and 50.0%, respectively, the IAA content of the fourth-order tube decreased by 25.5%, and the GA3 and ABA contents increased by 22.0% and 12.2%, respectively. The IAA, GA3, and ABA contents of the flesh and fruit stalk did not significantly differ from those in the calyx tube. The results indicated that spraying IAA during flowering promoted calyx persistence, whereas spraying TIBA promoted calyx abscission. These findings provide certain theoretical references and practical criteria for improving the quality of ‘Korla’ fragrant pear.
Yan Chen, Min Jin, Cui-yun Wu, and Jian-ping Bao
Tricia Jenkins, Chieri Kubota, Cary L. Rivard, and Eleni D. Pliakoni
Ethylene sensitivity of grafted and nongrafted tomato (Solanum lycopersicum) seedlings with three to four true leaves was examined. The concentration of exogenous ethylene that produced symptoms was between 1 and 10 µL⋅L–1 regardless of grafting. Symptoms of ethylene exposure included leaf epinasty, decreased maximal photochemical quantum yield of photosystem II (F v/F m), and increased plant height (nongrafted only). Grafted plants maintained higher F v/F m than nongrafted plants in response to higher ethylene concentrations. Ethylene-damaged plants showed comparable growth to the control plants 3 weeks after transplanting, but transplant quality was diminished as a result of ethylene exposure at high concentrations.
Benjamin Pease, Grant L. Thompson, and Adam W. Thoms
Soil degradation during construction often results in soil loss through erosion and reduced vegetation establishment. Composted organic materials are used to restore soil health of compromised urban soils when planting trees and shrubs; however, less is known about compost amendments for turfgrass establishment. The objective of this trial was to determine the effects of differing compost incorporation rates in two soil types on perennial ryegrass [PR (Lolium perenne)] establishment. The hypothesis was that as compost incorporation rates increase, turfgrass germination would increase until the compost rate becomes detrimental to turfgrass germination because of increased nitrate content and electrical conductivity (EC) levels. A salt-sensitive PR cultivar and a salt-tolerant PR cultivar were seeded into a loam topsoil and a clay subsoil at soil:compost volume ratios of 100:0, 80:20, 70:30, 60:40, 50:50, 40:60, and 0:100 using a mixed-source mature compost. Percent green cover (PGC) and leachate pH, EC, and nitrate content were measured during the 5-week establishment period. This trial showed that with a suitable topsoil, compost incorporation may be unnecessary to obtain acceptable PGC, but that compost additions (30% to 40%) to a clay subsoil achieve faster establishment while limiting the potential for reduced establishment because of increased nitrate content or EC associated with greater levels of compost incorporation. The EC or pH of soil:compost leachate was not found to predict turfgrass establishment. This trial suggests that soil type should be considered when making compost use rate recommendations; however, further research is needed to link compost physiochemical properties to compost use rates.
Mark K. Ehlenfeldt, James J. Polashock, Lisa J. Rowland, Elizabeth Ogden, and James L. Luteyn
Vaccinium meridionale (section Pyxothamnus), a tetraploid species native to higher-altitude locations in Jamaica, Colombia, and Venezuela, is of interest to Vaccinium breeders for its profuse, concentrated flowering, vigor, and monopodial plant structure, all of which may be useful in breeding for mechanical harvest in blueberry. In this study, tetraploid V. meridionale was successfully hybridized as both female and male with 2x Vaccinium vitis-idaea (section Vitis-idaea, lingonberry). The resultant F1 hybrids with lingonberry were both 3x and 4x, respectively. These hybrids were intermediate in morphology and notably vigorous. Most appear to be evergreen, with small, red-colored fruit. The 4x F1 hybrids displayed good fertility as females in backcrosses to both lingonberry and V. meridionale. Pollen production and quality were evaluated as an indicator of male fertility. Most clones had good pollen shed and high frequencies of well-formed tetrads. The overall fertility suggests that these hybrids, despite being derived from intersectional crosses, might be conventionally used for breeding without substantial difficulty.
Jason D. Lattier and Ryan N. Contreras
Althea (Hibiscus syriacus) is a popular shrub known for its vibrant summer blooms and winterhardiness; however, althea produces capsules with numerous seeds that germinate and cause a nuisance in production and the home landscape. Breeding for sterile forms has long been a goal of Hibiscus breeders, yet many popular “sterile” cultivars have been reported as weedy. The purpose of this study was to evaluate female and male fertility of tetraploid and hexaploid cultivars, and to evaluate the female fertility of pentaploid progeny resulting from 4x × 6x and 6x × 4x crosses. More than 600 self-pollinations were performed on 21 cultivars, yet only 24% of self-pollinations resulted in filled capsules, for an overall rate of four seeds per pollination. Significant differences were observed among taxa for seeds per capsule and seeds per pollination. Highest capsule set was observed on self-pollinated White Chiffon® and Pink Chiffon®. Anecdotally, we observed reduced vigor in the S1 generation of most taxa. However, ‘Woodbridge’ produced vigorous seedlings through the S2 generation. More than 2000 cross-pollinations were also performed, resulting in more than 15,000 seeds. To evaluate female fertility, 28 taxa were pollinated with a variety of male parents. Fertility was measured as seeds per capsule and seeds per pollination. Significant differences were found among taxa within and among flower forms (single, semidouble, and double) for seeds per capsule and seeds per pollination. Double-flowered forms had reduced female fertility. Taxa previously reported to be sterile were found to be fertile, including ‘Aphrodite’, ‘Diana’, ‘Helene’, and ‘Minerva’. Two hexaploids, ‘Pink Giant’ and Raspberry Smoothie™, had reduced female fertility compared with tetraploids. Male fertility was estimated for 20 cultivars by pollinating between one and 23 cultivars. For male fertility, significant differences were found among taxa for seeds per capsule and seeds per pollination; however, no significant differences in male fertility were observed among flower forms. Four taxa had relatively high fertility with more than 10 seeds per capsule and seeds per pollination, including Blue Satin®, Lil’ Kim™, Bali™, and Tahiti™. In addition to the significant differences among female and male fertility of each taxon, capsule set varied widely among individual cross combinations. Significant differences of female fertility were found in pairwise comparisons between almost all pentaploid taxa and the mean of tetraploid control cultivars. No difference in percent seed germination was observed between 4x × 6x and 6x × 4x crosses (45% and 45%, respectively) but both were significantly lower than seeds from open-pollinated tetraploids (89%). The reduced fertility of pentaploids will likely lead to new reduced fertility or sterile cultivars for the nursery industry, especially if combined with double flowers.
Mark H. Brand and Shelley N. Durocher
Fengyi Li, Ling Wang, Zhiyang Liu, Wangbin Ye, Lei Yan, Juan Yang, Xi Chen, Wanjie Men, and Lijuan Fan
Timothy Coolong, Kate Cassity-Duffey, and Andre Luiz Biscaia Ribeiro da Silva
Georgia is a leading fresh market cabbage (Brassica oleracea var. capitata) producer. Current recommendations for bare-ground cabbage grown in the Coastal Plain of Georgia indicate 175 to 225 lb/acre nitrogen (N). Approximately one-third of N fertilizer is recommended at planting, with two or three additional side-dress applications during the season. Growers have begun banding liquid fertilizer between four and six times during the season to reduce N leaching and enhance productivity. To determine the validity of current recommendations as well as the efficacy of applying periodic liquid fertilizer throughout the growing season, field experiments were conducted in Tifton, GA in Fall 2016 and 2017 with the cabbage cultivar Cheers. Fertilizer N rates were 175, 200, 225, and 250 lb/acre N applied using equivalent preplant fertilizer (50 lb/acre N) with two posttransplant applications of a granular fertilizer (27–0P–0K–5Ca) or six applications of a liquid fertilizer (9N–0P–0K–11Ca). A factorial, randomized, complete block design was used. There were no interactions among fertilizer program, N rate, or year for cabbage yield or nutrient concentrations. Total yield was unaffected by the N rate. However, plants fertilized with the lowest N rate (175 lb/acre N) had the lowest yields from the first two harvests compared with the other N rates. Nutrient concentrations were affected by year, with 2017 having greater concentrations of most macronutrients compared with 2016. In conclusion, the application of 175 lb/acre N led to a potential delay in harvest, but all other N rates were equal. The application method did not impact yield or earliness, suggesting that current recommendations for fertilizer applications after planting cabbage in Georgia are adequate.