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Grape (Vitis) production and fruit quality traits such as cluster size, berry shape, and timing of fruit development are key aspects when selecting cultivars for commercial production. Molecular markers for some, but not all, of these traits have been identified using biparental or association mapping populations. Previously identified markers were tested for transferability using a small (24 individual) test panel of commercially available grape cultivars. Markers had little to no ability to differentiate grape phenotypes based on the expected characteristics, except the marker for seedlessness. Using a biparental interspecific cross, 43 quantitative trait loci (QTLs) (previously identified and new genomic regions) associated with berry shape, number, size, cluster weight, cluster length, time to flower, veraison, and full color were detected. Kompetitive allele-specific polymerase chain reaction markers designed on newly identified QTLs were tested for transferability using the same panel. Transferability was low when use types were combined, but they were varied when use types were evaluated separately. A comparison of a 4-Mb region at the end of chromosome 18 revealed structural differences among grape species and use types. Table grape cultivars had the highest similarity in structure for this region (>75%) compared with other grape species and commodity types.

Open Access

Grafting can be a useful technology to improve productivity of vegetable crops, including tomato, particularly under the serious challenges of climate change for agricultural systems. This study aimed to evaluate the impact of some local tomato interspecific hybrid rootstocks along with Maxifort on the vegetative growth, productivity, and fruit quality of tomato under field production conditions. Heat-tolerant tomato hybrid 023 F1 was used as a scion over the two late summer seasons of 2021 and 2022. Grafting 023 F1 onto Maxifort or KFS-16 rootstocks resulted in the maximum plant growth. Similarly, Maxifort and KFS-16 rootstocks significantly increased the fruit setting percentage from 22.2% to 23.5% and 17.8% to 24.6%, total fruit yield from 33.5% to 53.7% and 29.6% to 51.6%, and marketable yields from 34.1% to 56.0% and 27.3% to 56.7%, respectively, during both seasons compared with nongrafted plants. These two rootstocks enhanced nutrient (nitrogen, phosphorus, potassium) uptake compared with nongrafted planted. However, grafting with the interspecific hybrid rootstocks (KFS-8 and KWS-9) significantly decreased the content of catalase, peroxidase, and proline, which might be associated with lower plant vigor and yield in these rootstocks. All rootstocks had an impact on fruit chemical composition; however, generally, Maxifort and KFS-16 had greater contents of vitamin C, β-carotene, and total antioxidants than nongrafted plants. KFS-16 had also greater lycopene content than nongrafted plants. These results demonstrate the potential use of Maxifort and local rootstock KFS-16 to boost the growth and yield of tomato plants under high-temperature stress in the late summer season.

Open Access

Electric lighting is often necessary to achieve a target daily light integral (DLI) for the production of high-quality young annual bedding plants (plugs). Early in production, plugs have a low leaf area index that limits light interception and likely results in wasted radiation supplied by electric sources. Previous research has shown that the addition of far-red radiation (700–780 nm) to the radiation spectrum in sole-source lighting experiments or the use of end-of-day far-red (EOD-FR) radiation treatments can promote an increase in leaf expansion and leaf area for many species. However, leaf expansion in response to far-red radiation may depend on other factors such as the ratio of red (600–699 nm) to far-red radiation (R:FR) and air temperature. Thus, the objectives of this work were to examine the effects of far-red radiation applied throughout the photoperiod and as an end-of-day radiation treatment on the morphology of petunia ‘Dreams Midnight’ seedlings grown under different temperature conditions. Specifically, petunia seed was sown in 128-cell trays and moved to one of two growth chambers set at 16 or 21 °C when cotyledons unfolded. Seedlings received an equal total photon flux density (400–780 nm) of 164 µmol·m−2·s−1 for a 17.25-hour photoperiod, and either a high (∼10.7) or low R:FR (0.5). Low R:FR-treated seedlings were grown at a constant temperature of either 16 or 21 °C and placed under blackout conditions at the end of the photoperiod. High R:FR-grown seedlings received either a 1-hour end-of-day white (EOD-W) or EOD-FR treatment at the end of the photoperiod, and were grown at a constant 16 or 21 °C; one EOD-FR treatment was also shifted from the 21 °C chamber to the 16 °C at the end of the photoperiod for both the EOD-FR treatment and subsequent dark period. Seedlings were harvested at 21 and 28 days after treatment initiation. For petunia seedlings grown at 21 °C, EOD-FR treatments had minimal effect on morphology or dry mass as all measured parameters, including total and average leaf area and stem length, were similar to EOD-W treatments. In contrast, low R:FR-treated seedlings showed responses characteristic of plants grown under shade, including significant stem elongation, an increase in total and average leaf area, and a reduction in leaf mass per unit area. As expected, production at 16 °C slowed the growth of petunia seedlings resulting in much smaller plants compared with the 21 °C grown plants, but shade responses such as elongated leaves and stems under a low R:FR were apparent. The EOD-FR–treated seedlings that received the diurnal temperature shift also showed reduced leaf area and dry mass compared with their constant 21 °C counterparts. Shade responses were observable at both 16 and 21 °C for low R:FR-grown plants, but the quantifiable impact of temperature on far-red responses could not be fully determined in the present study. Further research is warranted investigating crop responses to far-red radiation as well as potential interacting environmental factors as the promotion of morphological responses, such as leaf expansion, early in production may prove a useful strategy.

Open Access

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