Passiflora incarnata L., commonly known as maypop, is a wild passion fruit native to many areas of the eastern and southern United States where the climate ranges from subtropical to temperate. Although P. incarnata has had little attention paid to it for breeding purposes, it could be used in breeding for fruit production and possibly contribute cold hardiness genes in combination with other Passiflora species. The study was performed in 2018, 2019, and 2021 at the Mississippi State University South Mississippi Branch Experiment Station in Poplarville, MS, United States. Passiflora propagules were collected from various locations: Florida (FL), Illinois (IL), Mississippi (MS), Missouri (MO), and Oklahoma (OK). Of the 122 flowers across the five P. incarnata genotypes from differing locations, none of them produced a fruit or had any indication of successful or partially successful fertilization when selfed, indicating strong self- incompatibility. If self-compatibility does exist in nature, it is likely to be rare. However, certain combinations of P. incarnata from different locations produced successful fruiting, including IL × MO (52% success), FL × MO (85%), FL × OK (80%), MS × OK (40%), MO × IL (50%), MO × OK (40%), and OK × MO (80%). The differences across provenances show that incompatibility exists within P. incarnata but can depend on location. Overall, fruit weight, fruit size, and soluble solids content measured in this study were similar to and, in some cases, greater than those previously reported. These differences help to illustrate the diversity within P. incarnata and the still-untapped potential for breeding improvements. The problem of self-incompatibility is complex and there is much to learn about how Passiflora species, especially P. incarnata, function. Much of the U.S. domestic market is not familiar with passion fruit, especially as a table fresh product. This could be a barrier to adoption, but it could also prove to be an opportunity to create a niche within the present market and expand it. Although maypop fruit quality is not equal to that of Passiflora edulis Sims, selecting superior wild genotypes with desirable attributes to be used in future intra- and interspecific breeding is possible based on the results of this study.
Barbara J. Smith, Amir Rezazadeh, Eric T. Stafne, and Hamidou F. Sakhanokho
Supplemental lighting is frequently used to extend daylength for strawberries (Fragaria ×ananassa) grown in greenhouses and high tunnels; however, information is limited on the effect of these lights on disease development. We evaluated the effect of ambient light and six supplemental light treatments [red, blue, and white light-emitting diodes (LEDs), separately; a combination of red, blue, and white LEDs; wide-spectrum fluorescent (WSF); and WFS + ultraviolet B (UV-B)] on plant growth and disease response of strawberries grown in a greenhouse. Plants were exposed to supplemental light treatments for 17 h each day. In the WSF+UV-B treatment, plants were exposed to WSF light during the day and to UV-B light for 3 hours during the night. Two trials were conducted; each trial contained five or six cultivars and was replicated three times. Twice during each trial, detached leaves from each cultivar in each light treatment were inoculated with a conidial suspension of the anthracnose crown rot pathogen, Colletotrichum gloeosporioides and rated for disease severity 10 days later. There was a significant difference due to light treatment and to cultivar in relative chlorophyll content and plant growth parameters. Plant injury ratings were lowest in the white LED, WSF, and WSF+UV-B treatments. Plants in the combination LED and red LED light treatments received higher injury, lower vigor scores, and lower relative chlorophyll content values than plants in all other light treatments. After inoculation of detached strawberry leaves with C. gloeosporioides in Trial 1, there was a significant effect due to light treatments on disease severity ratings (DSRs) after 18 weeks’ exposure to light treatments with the DSRs in the WSF+UV-B treatment being lower than those in all other treatments except those in the red LED treatment. There was not a significant effect in DSRs due to light treatments after 24 weeks in Trial 1 or after 4 or 22 weeks in Trial 2. There were significant effects due to cultivar on DSRs in both trials: ‘Strawberry Festival’, ‘Pelican’, and ‘Seascape’ received the lowest DSRs. This study showed an effect of supplemental light on several strawberry plant growth parameters, including a harmful effect of high-intensity red LED irradiation.
Teal Hendrickson, Bruce L. Dunn, Carla Goad, Bizhen Hu, and Hardeep Singh
Hydroponic systems have become increasingly popular for growers in recent years for year-round local production. Whereas optimal air temperature for plant growth has been considered, optimal root zone temperatures have not been examined as thoroughly. The objective of this research was to determine the optimal water temperature for growing different types of basil hydroponically. Research was conducted at the greenhouses in Stillwater, OK. Seventeen cultivars were selected from six main types of basil and transplanted into Nutrient Film Technique hydroponic systems, and three water temperature treatments were applied: 23, 27.5, and 31 °C. Height, width, average leaf area, leaf number, chlorophyll concentration (chlorophyll readings obtained with the Minolta-502 SPAD meter), shoot fresh weight, shoot dry weight, and root dry weight were evaluated. In general, the 27.5 and 31 °C treatments were not greater than each other in terms of leaf number and root dry weight but were greater than the 23 °C treatment. The 31 °C treatment had the greatest height, whereas width, average leaf area, shoot fresh weight, and shoot dry weight were not different from the 27.5 °C treatment. The 23 °C treatment had the greatest chlorophyll concentration (SPAD) value. Cultivar differences were significant in average leaf area and SPAD, with ‘Spicy Bush’ having the smallest leaf area and purple basil having the greatest SPAD value. For all cultivars except purple basil and ‘Large Leaf Italian’, a 27.5 °C water temperature would be recommended for greater plant growth.
Biwek Gairhe, Peter Dittmar, Davie Kadyampakeni, Ozgur Batuman, Fernando Alferez, and Ramdas Kanissery
The use of glyphosate as a post-emergent weed management tool is crucial in Florida citrus production. However, extensive and nonjudicious application of glyphosate has drawn increasing concerns about its inadvertent effects on citrus, mainly linked to its possible impacts on preharvest fruit drop. Our study investigated the effect of applying glyphosate in the tree rows near the fruit harvesting window on fruit drop and yield in ‘Valencia’ sweet orange. Field trials were conducted at Southwest Florida Research and Education Center, Immokalee, FL. The experiments had a randomized complete block design with four replications. Three different doses of glyphosate within the labeled range of rates in citrus (i.e., low, medium, and high at 0.84, 2.10, and 4.20 kg acid equivalents of glyphosate per hectare, respectively) along with a water control treatment were sprayed in ‘Valencia’ citrus tree rows close to the harvesting period and assessed for their effects on preharvest fruit drop and yield. Our findings show that glyphosate application near the harvesting window may influence the fruit detachment force (FDF) in Valencia citrus; however, no significant effect on increasing fruit drop or reducing yield was observed during this 2-year study.
Sofía Gómez and Celina Gómez
Biostimulant products have various reported benefits for plant production in the field or using hydroponic systems in protected structures. However, limited information is available describing their potential use for indoor farming applications. Considering that lettuce (Lactuca sativa) is one of the most popular crops produced in commercial indoor farms, the objective of this study was to compare growth and quality of lettuce grown indoors using nine biostimulant products derived from humic substances, amino acids, hydrolyzed proteins, or seaweed extracts. ‘Monte Carlo’, ‘Fairly’, and ‘Lalique’ lettuce were grown hydroponically for 30 to 33 days under a daily light integral, day/night temperature, relative humidity, and carbon dioxide concentration of ≈13 mol·m‒2·day‒1, 22/21 °C, 70%, and 800 µmol·mol‒1, respectively. There were no positive effects from using any of the biostimulant products evaluated in our study as growth (leaf area, leaf number, shoot diameter, and shoot and root dry weight), yield (shoot fresh weight), and quality (bolting, tipburn index, leaf color, and SPAD index) of treated plants were generally similar to those from the untreated control. Applications from one seaweed extract caused slight negative growth effects, possibly due to phytotoxicity. Cultivar differences showed that Fairly plants had the highest susceptibility to tipburn and bolting, and none of the biostimulant products countered these symptoms. Overall, the products evaluated provided marginal advantages for indoor hydroponic lettuce production.
Svoboda V. Pennisi, Mussie Habteselassie, Genti Kostandini, and Freddie C. Waltz Jr.
Golf course superintendents are often under pressure to maintain high-quality turf. Such demand entails use of inputs, which can include biostimulants that are often marketed as a way of combating plant stress and improving turf quality. However, the extent of their use by superintendents and their level of efficacy are not well understood. This survey study was designed to better describe biostimulant use by the golf industry and to gain insights on the research needs of superintendents to address them effectively. A survey instrument was developed using online software and included a total of 13 questions relating to general familiarity with biostimulants and specific familiarity with five biological products. The instrument was disseminated electronically via the online survey tool to attendees (N = 80) during the annual conference of the Georgia Golf Environmental Summit in 2022. The respondents were from 62 golf courses, geographically representing the entire state of Georgia. The response rate was 62.5%. The majority of the respondents (86%) were familiar with biostimulants. The main reason for using biostimulants was predominantly agronomic, indicating a focus on turf performance and aesthetics. Of the respondents who used biostimulants, the overwhelming majority (93%) use humic acids and plant growth hormone-containing biostimulants. Respondents also indicated that research in microbial products would be the most relevant to the industry. This may be explained by the challenges in using such products (shelf life and microbial survival in soil). In conclusion, the survey indicated that Georgia golf course superintendents have high a level of familiarity with biostimulants. The survey yielded useful results to help formulate future research objectives to better serve the Georgia golf course industry.
Asmita Paudel and Youping Sun
Albizia julibrissin (mimosa tree) and Sophora japonica (Japanese pagoda tree) are drought-tolerant landscape plants; however, salinity responses of these two species are not well documented. The objective of this study was to investigate the morphological and physiological responses of these two species to three salinity levels in greenhouse conditions. Two studies were conducted in the summer/early fall of 2020 and the spring of 2021. In 2020, uniform plants were irrigated weekly for the first 2 weeks and every other day for the following 3 weeks with a nutrient solution at an electrical conductivity (EC) of 1.2 dS·m−1 as a control or saline solution at ECs of 5.0 or 10.0 dS·m−1. In 2021, plants were irrigated weekly for 8 weeks with the same treatment solutions as described previously. Albizia julibrissin and S. japonica survived in both experiments with minimal foliar salt damage (leaf burn or necrosis). Irrigation water at ECs of 5.0 and 10.0 dS·m−1 reduced plant height and dry weight (DW) of both species. In the fall experiment, A. julibrissin irrigated with a saline solution at an EC of 10.0 dS·m−1 had the highest reduction in plant height (61%) compared with the control. Albizia julibrissin and S. japonica irrigated with a saline solution at an EC of 10.0 dS·m−1 had 52% and 47% reductions in shoot DW compared with the control, respectively. In the spring experiment, compared with the control, there were 72% and 45% reductions in height of A. julibrissin and S. japonica, respectively, when irrigated with saline solution at an EC of 10.0 dS·m−1. In addition, compared with the control, A. julibrissin and S. japonica had 58% and 64% reductions in shoot DW, respectively, when irrigated with saline solution at an EC of 10.0 dS·m−1. Increasing salinity levels in the irrigation water also reduced leaf greenness [Soil Plant Analysis Development (SPAD)], leaf net photosynthesis rate (Pn), stomatal conductance (g S), and transpiration rate (E) of both species. Furthermore, sodium (Na+) and chloride (Cl−) concentrations in leaves were affected by elevated salinity levels in the irrigation water. Visual score, Pn, g S, and E negatively correlated to Na+ and Cl− concentrations in leaves. But Cl− accumulation had more impact on the growth of A. julibrissin and S. japonica. In summary, both species were tolerant to saline solution irrigation up to 5.0 dS⋅m−1 and moderately tolerant to saline solution irrigation up to 10.0 dS⋅m−1.
Uttara C. Samarakoon and James E. Faust
Clematis (Clematis ×hybrida) has not traditionally fit into the standard production system for vegetatively propagated herbaceous perennials because of the lack of commercially available unrooted cuttings and relatively poor rooting success. We investigated strategies to improve stock plant production and propagation of clematis. The first experiment compared the propagation performance of four cultivars (H.F. Young, Reiman, Little Duckling, and Pinky). The second experiment examined cutting productivity and propagation performance of clematis cultivars when stock plants were grown at 21 or 27 °C and propagated with or without the application of rooting hormone. Stock plants grown at 27 °C resulted in greater cutting numbers and greater dry weights in the rooted cuttings after propagation. The third experiment demonstrated the effects of the origin of the cuttings of the stock plant on cutting productivity and propagation performance. When shoots emerged from underground buds, as compared with axillary buds, the numbers of cuttings and fresh and dry weights of the rooted cuttings were increased by nearly 50%. The promotion of shoot emergence from underground buds on the stock plants led to continuous cutting production for five cycles, with cutting number increasing from 67 to 128 cuttings/plant. Year-round cutting supplies can be achieved by trimming stock plants to the substrate surface to promote juvenile shoot development while maintaining stock plants under long-day photoperiods and warm temperatures (27 °C).