Water shortage is one of the major challenges faced by the current agricultural systems worldwide, especially in arid and semi-arid regions. Deficit irrigation (DI), a water-saving strategy of applying less water than crop evapotranspiration (ETc) demands, has been extensively investigated in different crops, including water-intensive vegetables. The DI strategies such as regulated deficit irrigation (RDI) and partial root zone drying (PRD) generally increase water use efficiency (WUE) and have emerged as potential practices to save water for agricultural sustainability. However, in view of the sensitivity of shallow-rooted vegetable crops to water stress, DI is often associated with yield losses. A review of 134 DI reports of vegetable crops revealed significant reductions in yield under all DI levels in 52% of cases and yields statistically similar to those of full irrigation (100% ETc in most cases) under small water deficits in 44% of cases, thereby raising concerns about the sustainability of vegetable production under DI. Biochar, a carbon-rich co-product of pyrolysis of organic matter, is increasingly undergoing study as a soil amendment to mitigate drought stress and is being explored as an additional practice with DI to minimize the yield losses due to water deficits. This work reviews the effects of biochar application on growth, yield, physiology, and WUE of different vegetable crops under DI regimes to determine the potential of biochar and DI used in combination to sustain vegetable productivity in water-limited areas. Overall, the addition of biochar under DI has helped to compensate for yield losses of vegetables and further enhanced WUE. However, field studies investigating long-term soil–biochar interactions that strongly conclude the impact of biochar under moisture stress conditions are lacking.
Manpreet Singh, Rupinder Kaur Saini, Sukhbir Singh and Sat Pal Sharma
Fátima Medina-Lara, Ramón Souza-Perera, Manuel Martínez-Estévez, Manuel O. Ramírez-Sucre, Ingrid M. Rodríguez-Buenfil and Ileana Echevarría Machado
The characteristics of the soil in the Peninsula of Yucatán confer unique organoleptic properties to the habanero pepper (Capsicum chinense Jacq.), and thus this entity possesses the denomination of origin of the species, making these chilis the most coveted, nationally and internationally. However, the extreme microtopographic variation distinguishing the Peninsula complicates the transfer of technologies and the successful establishment of agricultural practices. Maya farmers of the region identify the brown soils as preferable for the cultivation of this chili, although there is some controversy among the farmers regarding the best yields when the quality of the water used for irrigation is poor. No studies of the effect of soil type on this plant have been carried out. This work evaluated the impact of three types of soil of the Peninsula (red, brown, and black) on growth, fruit production, and nutrient content in soils and plants, during different phenological stages. The results indicate that the red and brown soils were the best for the growth and production of the fruit. In the black soil, it was possible to observe greater retention and accumulation of sodium applied in the water used for irrigation and in the macronutrients N, P, K, which may have led to a negative effect in the development of the fruit in these plants. Moreover, the plants growing in red and brown soils seem to make a more efficient use of the nutrients, presenting higher values of N, P, and K in their tissues in the flowering-fructification stage. These results are particularly useful in the realization of agricultural plans with a lower consumption of fertilizers, which allows an increase in yield, particularly if we take into account the enormous problems of saline intrusion worldwide and in this region.
Chun-hui Shi, Xiao-qing Wang, Xue-ying Zhang, Lian-ying Shen, Jun Luo and Yu-xing Zhang
This study explored the effects of different colored bags (blue, green, white, yellow, orange, and red) on russet deposition on the peel of semi-russet ‘Cuiguan’ pears 10 days after full bloom (DAFB). The process of russeting of the peel and structure of the cork layer were characterized by microscopy and scanning electron microscopy (SEM), followed by the detection of lignin and the activity of enzymes involved in lignin synthesis. The expression of cinnamate-4-hydroxylase, 4-coumarate:coenzyme A ligase, cinnamyl alcohol dehydrogenase, cinnamoyl-CoA reductase, and peroxidase, which were related to phenylalanine ammonia-lyase, was determined via real-time quantitative polymerase chain reaction. Russeting of the outer peel of ‘Cuiguan’ pear accumulated rapidly at 80 DAFB, and a positive relationship between the russet index and lignin content was observed. Red and infrared (IR) ray, partial far-IR light (600–800 nm), and ultraviolet-A light (350–400 nm) promoted russeting in ‘Cuiguan’ pear peel, whereas green light decreased russeting, the russet index, enzymatic activities, and the expression levels of enzymes involved in lignin synthesis. Values of all these factors were higher for ‘Cuiguan’ pears in red bags than for those in bags of other colors. These findings suggested that spectral components affected the synthesis of lignin and the formation of fruit russet. Storage in green bags reduced russeting and improved fruit appearance.
Eric Hanson, Brent Crain and Katherine Hanson
Red raspberry cultivars that produce fruit on current-season canes (primocanes) can produce additional fruit the following year as second-year floricanes, termed double-cropping. The purpose of this study was to compare raspberry cultivars for double-cropping potential in a potted growing system under high tunnels in southwest Michigan. The cultivars Encore (floricane fruiting only), Imara, Josephine, Kwanza, Kweli, Nantahala, Nova, and Prelude were grown for 3 years in 11-L pots under a high tunnel. ‘Imara’, ‘Kweli’, and ‘Prelude’ produced the greatest total yields, averaging 2.7 kg/plant during the last 2 years. ‘Imara’ and ‘Kweli’ also produced large fruit that retained high fruit quality after storage. ‘Prelude’ was the earliest to ripen floricane fruit, and ‘Encore’, ‘Josephine’, and ‘Nanatahala’ were the latest. The start of primocane fruit harvest varied by year, but ‘Prelude’ was consistently one of the earliest. Overall, maintaining potted plants for multiple years reduced the cost of annual replacement, but older plants managed for floricane and primocane fruit production required additional pruning and training to control vigor.
Soon-Il Kwon, Jeong-Hee Kim, Sun-Ae Kim, Young-Soon Kwon and Jinwook Lee
Asmita Paudel, Ji Jhong Chen, Youping Sun, Yuxiang Wang and Richard Anderson
Sego SupremeTM is a designated plant breeding and introduction program at the Utah State University Botanical Center and the Center for Water Efficient Landscaping. This plant selection program introduces native and adapted plants to the arid West for aesthetic landscaping and water conservation. The plants are evaluated for characteristics such as color, flowering, ease of propagation, market demand, disease/pest resistance, and drought tolerance. However, salt tolerance has not been considered during the evaluation processes. Four Sego SupremeTM plants [Aquilegia barnebyi (oil shale columbine), Clematis fruticosa (Mongolian gold clematis), Epilobium septentrionale (northern willowherb), and Tetraneuris acaulis var. arizonica (Arizona four-nerve daisy)] were evaluated for salt tolerance in a greenhouse. Uniform plants were irrigated weekly with a nutrient solution at an electrical conductivity (EC) of 1.25 dS·m−1 as control or a saline solution at an EC of 2.5, 5.0, 7.5, or 10.0 dS·m−1 for 8 weeks. After 8 weeks of irrigation, A. barnebyi irrigated with saline solution at an EC of 5.0 dS·m−1 had slight foliar salt damage with an average visual score of 3.7 (0 = dead; 5 = excellent), and more than 50% of the plants were dead when irrigated with saline solutions at an EC of 7.5 and 10.0 dS·m−1. However, C. fruticosa, E. septentrionale, and T. acaulis had no or minimal foliar salt damage with visual scores of 4.2, 4.1, and 4.3, respectively, when irrigated with saline solution at an EC of 10.0 dS·m−1. As the salinity levels of treatment solutions increased, plant height, leaf area, and shoot dry weight of C. fruticosa and T. acaulis decreased linearly; plant height of A. barnebyi and E. septentrionale also declined linearly, but their leaf area and shoot dry weight decreased quadratically. Compared with the control, the shoot dry weights of A. barnebyi, C. fruticosa, E. septentrionale, and T. acaulis decreased by 71.3%, 56.3%, 69.7%, and 48.1%, respectively, when irrigated with saline solution at an EC of 10.0 dS·m−1. Aquilegia barnebyi and C. fruticosa did not bloom during the experiment at all treatments. Elevated salinity reduced the number of flowers in E. septentrionale and T. acaulis. Elevated salinity also reduced the number of shoots in all four species. Among the four species, sodium (Na+) and chloride (Cl–) concentration increased the most in A. barnebyi by 53 and 48 times, respectively, when irrigated with saline solution at an EC of 10.0 dS·m−1. In this study, C. fruticosa and T. acaulis had minimal foliar salt damage and less reduction in shoot dry weight, indicating that they are more tolerant to salinity. Epilobium septentrionale was moderately tolerant to saline solution irrigation with less foliar damage, although it had more reduction in shoot dry weight. On the other hand, A. barnebyi was the least tolerant with severe foliar damage, more reduction in shoot dry weight, and a greater concentration of Na+ and Cl–.
Debalina Saha, S. Christopher Marble, Brian Pearson, Héctor Pérez, Gregory MacDonald and D. Calvin Odero
The objective of this research was to determine how mulch type affects adsorption and efficacy of commonly used preemergence herbicides in nurseries and landscapes. Nursery containers were filled with standard potting media and mulched with either pine bark (PB) mini-nuggets (mixed Pinus sp.), pine straw (PS; mixed Pinus sp.), or shredded eucalyptus hardwood (HW; Eucalyptus sp.) at a 2-inch depth. Herbicides including dimethenamid-P + pendimethalin (applied as a tank mix), prodiamine, and indaziflam were applied to mulched containers, watered in, and the mulch was subsequently removed 3 days later. Seeds of garden spurge (Euphorbia hirta), large crabgrass (Digitaria sanguinalis), and eclipta (Eclipta prostrata) were then seeded and used as bioassay species for dimethenamid-P + pendimethalin, prodiamine, and indaziflam, respectively. Chemical assays were also performed using a separate set of pots mulched with PB at 2 inches and treated with the same herbicides. Results from the bioassay experiment showed PS was the only mulch type that did not significantly decrease efficacy of any applied herbicide. Chemical assays showed only 34% of the applied dimethenamid-P reached the soil surface as evidenced by chemical assay, but more dimethenamid-P moved through PB than did pendimethalin (12%) or prodiamine (17%), which adsorbed more strongly. Overall results suggest preemergence herbicides will be strongly adsorbed to organic mulch. However, as mulch is typically more effective on weeds that germinate below the mulch layer, this does not automatically result in reduced efficacy from herbicide + mulch combinations, and the addition of a preemergence herbicide may be effective in reducing weed germination within or on top of the mulch layer.
Kelly Nascimento-Silva, Luis Roca-Castillo, María Benlloch-González and Ricardo Fernández-Escobar
Silicon (Si) is the second most abundant element in the Earth’s crust. It is a nonessential element for plant growth, but it is considered beneficial because it can prevent biotic and abiotic stresses. Because nothing is known about the effects of Si in the olive, two experiments were performed with young plants of ‘Arbequina’ and ‘Picual’ cultivars to evaluate the effect of continuous Si applications on the incidence of olive leaf spot, the main foliar disease affecting this crop. Plants were grown in pots containing a mixture of washed sand and peat. In the first experiment, Si was foliar sprayed (foliar treatment) or applied to the soil through irrigation water (soil treatment) at the concentrations of 0, 2.5, 5, and 10 or 0, 1.25, 2.5, and 5 mg·L−1, respectively. The treatments were arranged in a completely randomized design for each cultivar. In the second experiment, the experimental design was a randomized complete block design in a 2 × 4 factorial arrangement, consisting of two forms of Si application (foliar vs. soil) and four concentrations (0, 5, 10, or 20 mg·L−1). Leaf Si concentration significantly increased with the amount of Si applied. After 5 months of treatments, plants were inoculated with a conidial suspension of the pathogen, and the disease index (DSI) was calculated. Shoot growth only increased in ‘Picual’ after Si application. The DSI showed a significant reduction in both cultivars treated with Si when compared with control plants, although differences between cultivars were observed.
Kate A. Ivancic, Matthew D. Ruark, Francisco J. Arriaga and Erin M. Silva
Spring-planted green manure cover crops may provide a nitrogen (N) benefit to a subsequent sweet corn (Zea mays L.) crop, but spring growth and lack of consistent benefits documented in previous studies provide limitations to adoption. Berseem clover (BC; Trifolium alexandrinum) and chickling vetch (CV; Lathyrus sativus L.) are two legumes that could be beneficial when spring-seeded, but they have not been well studied in this context. The objectives of this study were to measure spring-seeded cover crop biomass and N yield, and the subsequent effects on sweet corn yield and response to N fertilizer. The study was conducted in 2014 and 2015, and the experimental design was a randomized complete block split-plot design with cover crop as whole-plot treatments [CV, BC, berseem clover and oat (Avena sativa) mixture (BC + O), oats, and no cover crop] and N rate as split-plot treatments. Cover crop growth and effects on sweet corn production varied greatly between years, with both cover crop and sweet corn biomass greater in 2015, although BC produced very little biomass (<0.7 Mg·ha–1) and thus is not recommended for spring seeding. In 2014, CV resulted in the lowest agronomically optimum N rates (AONRs) compared with no cover crop, suggesting a potential N credit when only having an N yield of 11.6 kg·ha–1, but this effect was not seen in 2015. There was also no evidence that oat would supply N to the subsequent crop. Overall, evidence is lacking that any spring-seeded cover crop will provide a consistent N benefit on sandy soil, and limitations to spring growth may preclude widespread adoption.
Keun H. Cho, Joo Young Kim, Maria I. Alvarez, Veronica Y. Laux, Lauren K. Valad, Joshua M. Tester, Thomas A. Colquhoun and David G. Clark
Fluorescent proteins (FT) have become essential, biological research tools. Many novel genes have been cloned from a variety of species and modified for effective, stable, and strong expression in transgenic organisms. Although there are many applications, FT expression has been employed most commonly at the cellular level in plants. To investigate FT expression at the whole-plant level, particularly in flowers, petunia ‘Mitchell Diploid’ [MD (Petunia ×hybrida)] was genetically transformed with seven genes encoding FTs: DsRed2, E2Crimson, TurboRFP, ZsGreen1, ZsYellow1, rpulFKz1, or aeCP597. Each gene was cloned into a pHK-DEST-OE vector harboring constitutive figwort mosaic virus 35S promoter and NOS-terminator. These plasmids were individually introduced into the genome of MD by Agrobacterium tumefaciens–mediated transformation. Shoot regeneration efficiency from the cocultured explants ranged from 8.3% to 20.3%. Various intensities of red, green, and yellow fluorescence were detected from TurboRFP, ZsGreen1, and ZsYellow1-transgenic flowers, respectively, under ultraviolet light for specific excitation and emission filters. More than 70% of plants established from the regenerated shoots were confirmed as transgenic plants. Transgenic ZsGreen1 petunia generated strong, green fluorescence in all flower organs of T0 plants including petals, stigmas, styles, anthers, and filaments. Most of the chromophores were localized to the cytoplasm but also went into the nuclei of petal cells. There was a positive linear relationship (R 2 = 0.88) between the transgene expression levels and the relative fluorescent intensities of the ZsGreen1-transgenic flowers. No fluorescence was detected from the flowers of DsRed2-, E2Crimson-, rpulFKz1-, or aeCP597-transgenic petunias even though their gene transcripts were confirmed through semiquantitative reverse transcriptase-polymerase chain reaction. T1 generation ZsGreen1 plants showed green fluorescence emission from the cotyledons, hypocotyls, and radicles, which indicated stable FT expression was heritable. Four homozygous T2 inbred lines were finally selected. Throughout this study, we demonstrated that ZsGreen1 was most suitable for generating visible fluorescence in MD flowers among the seven genes tested. Thus, ZsGreen1 may have excellent potential for better utility as a sensitive selectable marker.