Peach (Prunus persica) fruit emit more than 100 volatile organic compounds. Among these volatiles, γ-decalactone is the key compound that contributes to peach aroma. The final step in lactones biosynthesis is catalyzed by alcohol acyltransferases (AATs). In this study, five AAT genes were isolated in the peach genome, and the ways that these genes contribute toward the peach aroma were studied. The sequence analysis of the five AATs showed PpAAT4 and PpAAT5 are truncated genes, missing important residues such as HXXXD. The expressions of PpAATs were investigated to identify the roles in creating the peach aroma. The results indicated that only PpAAT1 is highly expressed during γ-decalactone formation. A functional survey of the five PpAATs, using the oleaginous yeast expression system, suggested that only PpAAT1 significantly increased the γ-decalactone content, whereas the other four PpAATs did not significantly alter the γ-decalactone content. Enzyme assays on PpAATs heterologously expressed and purified from Escherichia coli indicated that only PpAAT1 could catalyze the formation of γ-decalactone. All results indicated that PpAAT1 is a more efficient enzyme than the other four PpAATs during the γ-decalactone biosynthesis process in peach fruit. The results from this study should help improve peach fruit aroma.
Bin Peng, Jianlan Xu, Zhixiang Cai, Binbin Zhang, Mingliang Yu, and Ruijuan Ma
Shengrui Yao, Robert Heyduck, Steven Guldan, and Govinda Sapkota
Jujube cultivars have been imported into the United States for more than 100 years, but cultivar trials have been limited. To accurately recommend cultivars for each region, trials have to be conducted. We have set up jujube cultivar trials at the New Mexico State University (NMSU) Alcalde (2015, USDA hardiness zone 6a), Los Lunas (2015, 7a), and Leyendecker (2017, 8a) Centers with over 35 cultivars at each site with two replicates and a complete random block design. We reported the early performance of fresh-eating cultivars in 2019. Here we report the performance of 19 drying and multipurpose jujube cultivars. Between 40% and 100% of jujube trees produced a few fruit to more than 100 fruit in the planting year, depending on cultivar and location. Trees were more upright at Los Lunas than at Alcalde. ‘Kongfucui’ (KFC) was the most productive cultivar at Alcalde with 13.3 kg/tree in 2019, followed by ‘Chaoyang’, ‘Jinkuiwang’ (JKW), ‘Pitless’, and ‘Lang’. The yield at Los Lunas was lower than Alcalde for the first 3 years after planting; however, ‘Jinsi 2’, ‘Jinsi 4’, ‘Jixin’, ‘Sherwood’, ‘Sihong’, and ‘Xiangzao’ produced higher yields at Los Lunas than Alcalde in 2019. All cultivars produced higher yields and contained higher soluble solids at Leyendecker than Alcalde and Los Lunas at similar ages. ‘JKW’ was the most vigorous and productive cultivar at Leyendecker. ‘JKW’, ‘Xiangzao’, and ‘Lang’ produced more than 3.0 kg/tree in their second year after planting. ‘JKW’ yielded 12.3 kg/tree in its third year after planting. Among the three locations, drying cultivars are not recommended for commercial production at Alcalde. However, home gardeners can plant multipurpose and early-drying cultivars at Alcalde. Leyendecker produced the best dry fruit with larger fruit size, rich color, and meaty fruit; dry fruit quality was acceptable in most years at Los Lunas except 2019. We preliminarily recommend some drying and multipurpose cultivars for each location. As trees mature and produce more fruit, we will fine-tune the cultivar recommendations. We also discuss the jujube cultivar zoning information in New Mexico and fruit uses.
Humberto Aguirre-Becerra, Juan Fernando García-Trejo, Cristina Vázquez-Hernández, Aurora Mariana Alvarado, Ana Angélica Feregrino-Pérez, Luis Miguel Contreras-Medina, and Ramón G. Guevara-Gonzalez
Light is an abiotic factor, and its quality, quantity, and photoperiod can be modulated to work as eustress inductors to regulate plant processes. It is known that red (R), blue (B), far-red (FR), and ultraviolet-A wavelengths can promote photomorphogenesis and secondary metabolite production in plants. Several ratios of R:B and the addition of end of-day FR, separately, have beneficial effects on plant development, whereas adding ultraviolet-A enhances the production of secondary metabolites such as phenols. However, the effects of extended photoperiods with a mixture of these four wavelengths and extra end-of-day FR have not been evaluated for plants of commercial interest. The objective of this study was to determine the effects on tomato seedlings (‘Saladette’, CORDOBA F1) of different overnight photoperiods using a fixed combination of R (625 nm), B (460 nm), FR (720 nm), and ultraviolet-A (410 nm). We expected increases in the production of specialized metabolites and the generation of beneficial changes in the seedling biomass and morphology. Four treatments involving overnight artificial light provided by a light-emitting diode (LED) module were established: TC (control), 0 h; T1, 4 hours; T2, 8 hours; and T3, 12 hours. All treatments were subjected to a 12-hour natural photoperiod and 12 hours of overnight artificial light. The experiment lasted 4 weeks, and plants were sampled every week for physical and phytochemical measurements. In general, seedlings subjected to 4-hour and 8-hour treatments presented better results than those subjected to the control and 12-hour overnight photoperiod treatments. Seedlings subjected to treatments with an 8-hour overnight photoperiod presented large accumulation of biomass in the stem rather than in the leaves because they had large stem dry weight, stem weight, and elongation and higher first, second, and third internode lengths; however, they had lower leaf area, leaf dry weight, and health index. Seedlings subjected to treatment with a 4-hour overnight photoperiod were visually bigger, with large leaf expansion, total length, stem weight, total weight, and specific leaf area; however, this treatment had a negative impact on the biomass accumulation, with lower leaf weight, stem dry weight, and health index. The 12-hour treatment had a negative impact on the leaf area, and thus the specific leaf area, of seedlings; however, the biomass accumulation was large, with higher leaf dry weight, total dry matter, and specific leaf area, but no difference in stem dry weight compared with the control. At the end of the experiment, the total phenolic content increased in all treatments compared with the control, but the flavonoid content decreased. Moreover, the antioxidant capacity was higher for T2 during the last 2 weeks of the experiment. Results are discussed according to the possibilities of using this light strategy for seedling production.
Yun Kong, Katherine Schiestel, David Llewellyn, and Youbin Zheng
Intercropping can increase land use efficiency in high tunnel crop production, but it may also lead to decreases in yield and quality of main crops due to the potential competition for resources. This study evaluated the agronomic viability of intercropping snow pea (Pisum sativum L., ‘Ho Lan Dou’) with cherry tomato (Solanum lycopersicum L. var. cerasiforme ‘Sarina hybrid’) without additional inputs of water and fertilizers on peas in an organic high tunnel production system under Southern Ontario climate conditions in Guelph, Ontario, Canada (lat. 43.5 °N, long. 80.2 °W) during 2015 and 2016. In each 80-cm-wide bed, the tomato crops were planted alternately in double rows spaced 30 cm apart, with in-row spacing of 110 cm, which resulted in a planting density of ≈24,000 plants/ha. The snow pea seeds were sown between the tomato plants (i.e., within the same beds as tomatoes) in holes (two seeds per hole), with four rows in each bed and in-row holes spaced 10 cm and at least 25 cm away from the tomato plants, which resulted in a seeding rate of ≈650, 000 seeds/ha. The same amount of water or fertilizer was applied to the intercropping and nonintercropping plots based on the needs of the cherry tomato plants. Plant growth, fruit yield, and quality were compared between tomato plants with and without intercropping. Intercropping with snow peas did not affect total marketable fruit yield, unmarketable fruit percentage, fruit quality traits (e.g., individual fruit weight, soluble solids content, dry matter content, and postharvest water loss), or early-stage plant growth of the cherry tomato. Therefore, it is at least an agronomical possibility to intercrop snow peas with cherry tomatoes on the same beds without additional inputs of water and fertilizer on snow peas in an organic high tunnel system. The additional yield of pea shoots or pods in the intercropping treatment also increased economic gross returns in the high tunnels, although the economic net return might vary with the costs of seeds and labor involved in snow pea growing.
Huan Hu, Nan Chai, Haoxiang Zhu, Rui Li, Renwei Huang, Xia Wang, Daofeng Liu, Mingyang Li, Xingrong Song, and Shunzhao Sui
Wintersweet (Chimonanthus praecox) is one of the most popular winter-blooming species. Effective vegetative propagation is necessary for commercial usage and protection of wintersweet. In the current study, the four factors, namely hormone type (A), hormone concentration (B), soaking duration (C), and medium (D), were assessed using an L16 (44) orthogonal test design. The hormone types include ABT (A1), α-naphthalene acetic acid (NAA) (A2), indole butyric acid (IBA) (A3), and indole-3-acetic acid (IAA) (A4); the hormone concentrations include 100 mg·L−1 (B1), 500 mg·L−1 (B2), 1000 mg·L−1 (B3), and 1500 mg·L−1 (B4); the soaking durations include 5 seconds (C1), 5 minutes (C2), 30 minutes (C3), and 3 hours (C4); and the mediums include perlite: peat in the ratios 1:0 (D1), 2:1 (D2), 1:1 (D3), and 1:2 (D4). The results showed that hormone and proper medium could significantly improve the cutting survival, rooting, and sprouting, whereas poor factor combinations, especially high hormone concentrations combined with long soaking durations may be threatened to the cuttings and rooting. In actual experiments, we successfully obtained an excellent rooting percentage (62.22%) of wintersweet from treatment No. 5 (A2B1C2D3), which is perlite and peat (1:1) as the medium and soaking the cuttings in 100 mg·L−1 NAA for 5 minutes as the hormone treatment. This combination can already meet the requirements for commercial production. A range analysis showed that the medium and hormone concentration were the most important factors affecting the cutting of wintersweet. An analysis of variance also showed that the medium and hormone concentration can significantly or extremely significantly affect most cutting indicators. Moreover, our results revealed that an orthogonal design method is an effective tool for establishing an improved technique for cutting propagation.
Mark K. Ehlenfeldt, Joseph Kawash, and James Polashock
There is ongoing interest in transferring new characteristics into commercial blueberry from other blueberry species. Vaccinium padifolium is a species distantly related to commercial blueberry that has traits of notable value to conventional blueberry development. Among these traits are upright structure, strong growth, abundant flowering and fruiting, superior self-fertility, fruit-cluster structure suited to mechanical harvesting, and repeat/continuous flowering. Previously produced F1 hybrids of V. padifolium × V. corymbosum were used in crosses with a variety of conventional blueberry selections to generate 13 backcross (BC1) families. The backcross families were evaluated under field conditions to determine their performance and to guide further use of this germplasm. The offspring varied considerably, but most families produced several individuals of acceptable commercial quality. The recovery of V. padifolium characteristics varied. Many plants bore evidence of V. padifolium plant structure, but none showed indications thus far of continuous or repeat flowering. The best selections from these families have been saved and will be intermated to generate the next cycle of this material. These clones will also be crossed to hybrid combinations of V. arctostaphylos and V. cylindraceum to further diversify and recombine this germplasm.
Hardeep Singh, Megha R. Poudel, Bruce Dunn, Charles Fontanier, and Gopal Kakani
Increase in ambient carbon dioxide (CO2) concentration is beneficial for plant growth due to increased photosynthesis and water use efficiency. A greenhouse study was conducted to investigate how supplemented CO2 influences optimal irrigation and fertilization management for production of two ornamental plants. Two identical greenhouses were used, with one having CO2 supplementation and the other serving as the control with ambient CO2 concentration. Tensiometer-based irrigation treatments were applied at soil tensions of –5, –10, and –15 kPa with 0-, 3-, 6-, or 9-g controlled-release fertilizer rates applied in factorial with irrigation treatments. Plugs of geranium ‘Pinto Premium Rose Bicolor’ and fountain grass were grown under experimental conditions for 12 and 16 weeks, respectively. The results showed that CO2 supplementation increased the dry weight of geranium ‘Pinto Premium Rose Bicolor’ and fountain grass by 35% and 39%, respectively. Under the two driest irrigation regimes (–10 and –15 kPa), photosynthesis of geranium ‘Pinto Premium Rose Bicolor’ increased with CO2 supplementation compared with the ambient condition. Similarly, for fountain grass, the moderately watered (–10 kPa) treatment had a greater rate of photosynthesis with greater fertilizer rates of 6 or 9 g. CO2 supplementation resulted in increased water use efficiency of both species, whereas rate of transpiration was lower only in fountain grass. Among different fertilizer rates, 6- or 9-g fertilizer rates had greater values for dry weight, number of flowers, and stomatal conductance in both species. Therefore, it can be concluded that CO2 supplementation can help in efficient use of water for greenhouse production of ornamental plants.
Ayoub Fathi-Najafabadi, Cristina Besada, Rebeca Gil, and Alejandra Salvador
Persimmon cultivation has significantly grown in the Mediterranean Region in recent years. The production concentrates mainly in three astringent cultivars: Kaki Tipo in Italy, Triumph in Israel, and Rojo Brillante in Spain. Therefore, the varietal range expansion is one of the current challenges for persimmon producers in this area. Moreover, the introduction of nonastringent persimmon cultivars is particularly interesting because they can be commercialized immediately after harvest without applying deastringency treatment before commercialization. This study evaluated the harvest period and the postharvest response of six Japanese nonastringent cultivars (Kanshu, Shinshu, Soshu, Suruga, Youhou, Izu). During two seasons, fruit from each cultivar were harvested at two maturity stages. Fruit quality (external color, firmness, and total soluble solids) was evaluated after harvest and after different commercial scenarios (domestic market: 7 days at 20 °C, market to European Union (EU): 5 days at 5 °C plus 5 days at 20 °C, and market to countries with cold-quarantine treatment requirements: 21 days at 0 °C plus 5 days at 20 °C). Cultivars Kanshu, Shinshu, Soshu, and Izu were identified as early cultivars, and Soshu was the earliest one, which reached commercial maturity at the beginning of September. These four cultivars showed good quality after simulating commercialization on domestic and EU markets. Cultivars Suruga and Youhou overlapped the current harvest window, but their low chilling injury sensitiveness is highlighted, so they are of special interest to be cold-stored at the end of the season to be commercialized in overseas markets.
Saquib Waheed, Yuan Peng, and Lihui Zeng
In fruit trees, flowering is a key event followed by fruit development and seed production. Gigentea (GI), a clock-associated gene, is known to contribute to photoperiodic flowering and circadian clock control in Arabidopsis thaliana. However, its functions in woody fruit trees remain unclear. In this study, a 2000 bp promoter fragment of the longan (Dimocarpous longan) DlGI gene was isolated from the genomic DNA of longan ‘Honghezi’ by polymerase chain reaction amplification. The DlGI promoter contained two main types of potential cis-acting elements: light-responsive and hormone-responsive elements. The promoter was fused with the β-glucuronidase (GUS) reporter gene of pBI121 to generate the pDlGI:GUS construct. GUS histochemical staining of transgenic A. thaliana revealed that DlGI might play a role in different developmental phases of longan. Exposure of transgenic A. thaliana to varying light intensities showed that the GUS activity increases with increased light intensity. Transient expression of pDlGI::GUS in Nicotiana benthamiana showed that the GUS activity was higher and reached peak a few hours earlier under short-day (SD) than long-day conditions. Exposure to different hormonal treatments revealed that the transcript level of GUS was activated by gibberellin (GA3) and indoleacetic acid (IAA) but suppressed by abscisic acid and methyl jasmonate treatment. In addition, N. benthamiana transient assay and dual-luciferase assay revealed that the presence of early flowering 4 (ELF4) homologs of longan (DlELF4-1 and DlELF4-2) significantly activated the DlGI promoter. The positive response of DlGI promoter to high light-intensity, SD photoperiod, GA3 and IAA signals, and DlELF4 transcription factor suggest that DlGI may function as a circadian clock and play a role in responding to SD conditions and other signals in flower initiation of longan.
Anna Underhill, Cory Hirsch, and Matthew Clark
Grape (Vitis vinifera) cluster compactness is an important trait due to its effect on disease susceptibility, but visual evaluation of compactness relies on human judgement and an ordinal scale that is not appropriate for all populations. We developed an image analysis pipeline and used it to quantify cluster compactness traits in a segregating hybrid wine grape (Vitis sp.) population for 2 years. Images were collected from grape clusters immediately after harvest, segmented by color, and analyzed using a custom script. Both automated and conventional phenotyping methods were used, and comparisons were made between each method. A partial least squares (PLS) model was constructed to evaluate the prediction of physical cluster compactness using image-derived measurements. Quantitative trait loci (QTL) on chromosomes 4, 9, 12, 16, and 17 were associated with both image-derived and conventionally phenotyped traits within years, which demonstrated the ability of image-derived traits to identify loci related to cluster morphology and cluster compactness. QTL for 20-berry weight were observed between years on chromosomes 11 and 17. Additionally, the automated method of cluster length measurement was highly accurate, with a deviation of less than 10 mm (r = 0.95) compared with measurements obtained with a hand caliper. A remaining challenge is the utilization of color-based image segmentation in a population that segregates for fruit color, which leads to difficulty in differentiating the stem from the fruit when the two are similarly colored in non-noir fruit. Overall, this research demonstrates the validity of image-based phenotyping for quantifying cluster compactness and for identifying QTL for the advancement of grape breeding efforts.