Browse

You are looking at 91 - 100 of 42,087 items for

Lettuce tipburn is a physiological disorder characterized by marginal necrosis and curling of inner, younger leaves caused by localized calcium deficiency, especially in low evapotranspiration environments that restrict mass flow and thus calcium mobility. Severe tipburn negatively affects the marketability and quality of greenhouse-grown hydroponic lettuce. We aimed to assess the effectiveness of a chemical-based, calcium-mobilizing biostimulant for mitigating lettuce tipburn when applied in hydroponic nutrient solutions. Butterhead lettuce (Lactuca sativa ‘Rex’) was grown indoors under warm-white light-emitting diodes at a mean photosynthetic photon flux density of 300 μmol⋅m−2⋅s−1 for 11 days. Subsequently, we transplanted seedlings into deep-water-culture hydroponic trays in a greenhouse at an air temperature of 24.6 ± 1.2 °C, relative humidity of 76.2% ± 7.4%, and 20-hour photoperiod with supplemental lighting from high-pressure sodium lamps. The plants were grown in nutrient solutions with and without the biostimulant codenamed CC US-2105 at two concentrations (22 and 220 μL⋅L−1). Data were collected from plant samples at three harvests at 14, 21, and 28 days after transplant (DAT). At 14 DAT, there was no tipburn under any treatments. Compared with the control, the biostimulant at 22 μL⋅L−1 increased shoot dry mass by 31%. At 21 DAT, the biostimulant at 220 μL⋅L−1 eliminated tipburn, and the biostimulant increased shoot fresh weight by 28%, irrespective of the concentration. At 28 DAT, despite sufficient calcium in the whole plant and the remaining nutrient solution, severe tipburn still occurred in plants that did not receive the biostimulant (control). Compared with the control, the biostimulant at the higher concentration of 220 μL⋅L−1 decreased the tipburn rating by 88% and the number of leaves with tipburn by 85%, increased the plant diameter by 11%, increased the total leaf number by six, and accumulated higher levels of manganese and zinc. In contrast, these parameters remained unaffected at the lower biostimulant concentration of 22 μL⋅L−1. At 28 DAT, shoot biomass was unaffected by the biostimulant. In conclusion, the calcium-mobilizing biostimulant is an effective strategy to mitigate hydroponic lettuce tipburn without decreasing biomass accumulation in greenhouse conditions.

Open Access

Little-leaf mockorange is a native plant species with desirable characteristics for landscape use. The need to conserve specific genotypes and the difficulty of seed propagation and stem cutting propagation make axillary shoot micropropagation a good option for this species. A series of experiments were completed individually with the goal to improve in vitro propagation protocols by evaluating different types of cytokinins [benzylaminopurine (BA), kinetin (Kin), zeatin (Zea), meta-topolin (MT), and thidiazuron (TDZ)] at 0, 1.1, 2.2, 4.4, or 8.8 µM. Selected minerals (0 to 60 mM or 0 to 45 mM N, 0 to 500 µM or 0 to 100 µM Fe, 0 to 3 mM Ca, 0 to 1.5 mM Mg, or 0 to 1.25 mM P) were also tested separately in the tissue culture medium; the base medium was ½ strength MS in these mineral experiments. At the end of each experiment (8 or 12 weeks), plant growth characteristics including number of axillary shoots, shoot height, and dry weight were determined. Of the six cytokinins tested, Zea produced the largest increase in shoot growth. Supplementation with 1.1 µM Zea resulted in the most shoot dry weight, almost 2.5-fold more than control shoots. Shoots on 0.55, 1.1, or 2.2 µM Zea were at least 64% taller than control shoots. Shoots placed on regular ½ strength MS basal salts, described above, and/or media lacking the nutrient of interest, were used as a positive and negative control treatments. For each separate mineral tested, the best concentration for optimum shoot growth was the concentration of that mineral used in ½ strength MS medium. A medium containing mineral concentrations of 30 mM N, 50 µM Fe, 1.5 mM Ca, 0.75 mM Mg, and 0.625 mM P, and 1.1 µM Zea should be used to produce the optimum in vitro shoot growth of little-leaf mockorange.

Open Access

Walnut, a woody plant, is regarded as having difficulty rooting when propagated by vegetative methods, such as cutting and layering. A layering experiment was conducted in 2018 and 2022. In 2018, some Juglans species, including J. regia L. seedling (JR), J. regia cv. Liaoning 1 (JR LN1), J. hopeinesis Hu seedling (JH), J. mandshurica Maxim seedling (JM), and J. nigra L. seedling (JN), were the mother plants. The specific research hypotheses were that own-rooted walnut propagule could be obtained through layering. the rooting capacity of different Juglans species would be different, and the rooting ability of JN would be the highest among the samplings. The results indicated that all of these species in the experiment could be rooted by etiolation and indole-3-butyric acid (IBA) treatment and that root occurrence was found 6 to 7 weeks after IBA treatment. The layers (shoots from the mother plant) on the seedlings of JR, JH, and JM obtained rooting percentages (RP) of 75.55%, 84.45%, and 86.67%, respectively, and root numbers (RNs) of 21.8, 42.8, and 38.8, respectively, after 20 days of etiolation and 1% IBA treatment. JR LN1 had difficulty rooting in equal conditions and had a RP of 31.11%. In 2022, JR LN1 was the only mother plant and the IBA concentration was increased to obtain satisfactory RP and RN. With the 4% and 8% IBA treatments, RPs of 88.9% and 93.3% and RNs of 40.3 and 27.7, respectively, were achieved. During the experiment, the RP, RN, root length (RL), and root diameter (RD), as well as the layer height (LH) and layer diameter (LD), were investigated and evaluated. Layers with low vigor were more likely to root, as shown by a nonparametric test conducted for the height and diameter of the layers of the rooting and nonrooting groups. A significantly negative correlation (r = −0.548) was observed between RN and LH. Moreover, the quality of the best results of JR LN1 layering propagule and that with ‘liaoning 1’ 1-year-old seedling were compared. Our results provide more support for the possibility of vegetative propagation of walnut by layering and more information regarding the clonal cultivation of walnut trees and the own-rooted seedling establishment of walnut cultivars.

Open Access

The color of vegetables is an important factor in consumer food choices and in cultivar choice by growers and processors for production. In absorbing a broad spectrum of light, leaves support plant development by influencing factors such as biomass accumulation, chlorophyll content, and reproductive growth. The edible organ of the snap bean (Phaseolus vulgaris L.) is the pod, and its color is not only one of the most important traits for commercial consideration, but also influences phytonutrient content. Although chlorophyll provides the base color, other compounds such as carotenoids and flavonoids may affect leaf and pod color. Darker yellow- or blue-green pods are preferred for processing, but there is more leeway for fresh market, with lighter-colored pods being acceptable. This research characterized leaf and pod color variation in the 378-member Snap Bean Association Panel. Leaf and pod colors were measured with a colorimeter using the L*a*b* scale, which was then transformed to L* (lightness), C* (chroma), and H° (hue angle) for analysis. Both green and wax bean accessions had predominantly green leaves, even though both exterior and interior colors of pods varied by accession. The leaves at the upper level in the canopy were lighter than lower and middle-level leaves. C* of leaves was similar across environments but leaves from the field were greener than leaves of greenhouse-grown plants when converted to Royal Horticultural Society (RHS) values, even though they had similar H°. L* did not differ for corresponding leaf positions of both field and greenhouse leaves. Purple pods were darker (lowest L*) and yellow pods were lighter (highest L*). Although wax beans had similar exterior and interior colors, accessions with purple exterior of pods had green interiors. Green pods were generally two times higher for L* and lower in C* compared with leaves. Pod interior L* was darker than exterior in both years. Pod exterior L* was not significantly different among accessions, whereas pod interior L* differed significantly between years. Broad sense heritabilities ranged from 0.69 to 0.88 for L*, 0.12 to 0. 87 for C*, and 0.81 to 0.89 for H°. Although greater variation was observed in pods than leaves, lower heritability was determined. Moderate correlations between leaf L* and the interior and exterior pod L* implies that it would be possible to select for pod color on the basis of leaf color, with verification using standard cultivars.

Open Access

Pea (Pisum sativum) dominant for the fundamental color gene A showed a high level of resistance to Globisporangium ultimum (formerly Pythium ultimum) seed rot. Reciprocal crosses demonstrated that, with our materials, such resistance was associated with the testa (seedcoat) phenotype but not the embryo phenotype. Dominance of A over a was complete for this trait. Neither wrinkled seed form (r) nor green cotyledons (i) diminished resistance when A was dominant, although both recessive alleles diminished resistance when seeds were borne on white-flowering (a) plants. The product of the A gene functions in the pathway leading to flavonoids, including proanthocyanidins (PAs) and anthocyanidins. We found that resistance to G. ultimum seed rot was closely associated with not only dominant A but also testa PAs and testa sclerenchyma. Even A testas that lacked anthocyanins but contained PAs and sclerenchyma showed a high level of seed rot resistance. Moreover, a mutation removing PAs and sclerenchyma in a narrow zone from the hilum to the radicle markedly increased susceptibility. The PAs in pea testas were predominantly prodelphinidins in seeds from purple-flowered plants (A B) and procyanidins from pink-flowered plants (A b). Compared with procyanidins, prodelphinidins have higher antioxidant activity but are more likely to sequester iron, a particular concern with dry pea. Although A B testas were more resistant than A b to seed rot, the difference seemed too slight to militate against growing pink-flowered pea. We stressed the need for more histological comparisons of A B and A b testas, and we indicated that genes and their phenotypic effects examined during the current study could be useful for modeling biosynthesis of PAs and related cell walls.

Open Access

Almond growers are seeking ways to reduce costs but maintain yield. Intensive planting systems with greater planting densities using trees on growth-controlling rootstocks, combined with mechanical pruning and shake-and-catch harvesting are becoming popular. In this study we examined the responses of six almond cultivars with distinctive architecture grafted onto five rootstocks with varying degrees of vigor control. Trees were planted in 2018 in a nursery row and left to grow without pruning until Winter 2021. Pruning involved a rudimentary hedging treatment akin to mechanical pruning. Branching and tree structure were recorded in 2020, before pruning, and again at the end of 2021, after one season’s growth following pruning. A rating system was developed to record qualitative data on central leader dominance and the number, length, basal diameter, and, in some cases, branching angle of axillary shoots and including scaffold branches. Relatively few changes were recorded in the basic growth habit of these trees in response to pruning. Before pruning, the most common rootstock effect was on axillary shoot production. After pruning, the most common rootstock effects were on scaffold branching and the length of subterminal axillary shoots. Further studies are required to determine how these differences produced by the interaction between pruning and rootstock may affect the productivity of fruit-bearing trees. Although in this study with young trees we were not able to record crop yield, the results highlight that it is mainly the scion–rootstock combination, with or without pruning, that determines the potential productivity of fruiting canopies. Scion–rootstock combinations that produce narrow upright canopies naturally with strong central leader dominance and highly branched canopies are preferred for superintensive growing systems with or without use of mechanical hedging.

Open Access

Different sources of cytoplasmic male sterility (CMS) are used to produce hybrid onion seed. The most commonly used source of CMS in onion is S cytoplasm (S-CMS), and male fertility is restored by a dominant allele at the nuclear male-fertility restoration locus (Ms). Male-sterile plants possess S cytoplasm and have the homozygous recessive genotype at Ms; seed propagation of male-sterile plants is possible by crossing with a male-fertile maintainer plant or inbred possessing normal (N) male-fertile cytoplasm and the homozygous recessive at the Ms locus (N msms). Some commercially important onion populations possess S-CMS and high frequencies of the dominant Ms allele, eliminating the possibility to develop maintainer lines. An alloplasmic source of CMS (Gal-CMS) was developed by backcrossing the cytoplasm of Allium galanthum into the nuclear background of onion. The advantage of Gal-CMS is that the dominant allele at Ms does not restore male fertility, making this source of CMS useful for the development of male-sterile lines from populations possessing S cytoplasm and dominant allele(s) at Ms. In this research, a single nucleotide polymorphism unique to the cytoplasms of A. galanthum and Gal-CMS was identified, useful to distinguish Gal-CMS from other onion cytoplasms.

Open Access

Perennial ryegrass (Lolium perenne L.) is one of the most widely used species for sports fields in temperate climates because of its high wear tolerance. However, wear tolerance of cultivars may vary according to local environmental conditions and turfgrass management. In this study, we evaluated the wear tolerance of six perennial ryegrass cultivars (Adagio, Apple SGL, Equate, Firebird, Principal 2, Tetradark) under two fertility treatments (100 or 200 kg N⋅ha−1⋅yr−1) over 2 years. The field trial was performed at the Experimental Agricultural Farm at the University of Padova in northeastern Italy in a silty loam soil. Plots were arranged in a randomized complete block with three replications and subjected to three traffic events per week using a sports field wear simulator. Turfgrass quality (TQ), percent green cover (PGC), and normalized difference vegetation index (NDVI) were recorded every 2 weeks and averaged over each month. Although perennial ryegrass cultivars responded differently to wear stress, the higher nitrogen (N) rate positively affected the TQ of them all. ‘Tetradrak’ and ‘Equate’ had the lowest TQ, especially during the active growing seasons (spring and autumn). However, ‘Tetradark’ was particularly negatively affected during the cool fall months. The impact of a higher N fertilization rate on PGC and NDVI appeared to be more pronounced in spring than in fall. Furthermore, slight differences among cultivars and treatments were observed in summer and winter when temperatures were a limiting growth factor.

Open Access