Volume 70

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Quest for the grassland jewels

Author: Q. Bersiks

PP: Pages 1-5

The Ornamental Horticulture programme group, Department of Environmental Sciences, UNISA, identified the need to recog-nize plant species of the Highveld region with ornamental, medicinal and ecofriendly landscape value for propagation and cultiva-tion. According to the World Wild life fund 2020 the status of the Highveld grasslands is critical endangered due to severe agricultural fragmentation and urbanisation. These factors as well as climate change and extreme weather phenomena necessitate to be proactive in the identification and propagation of plant species best suited and resilient to extreme climate conditions. Not only to fullfil the demands and needs of the green industry but also for the preservation of biodiversity. Many of these resilient characteristics already exhibited by many plant species of the grassland biome.

By making use of structured questionnaires and pilot studies, public inputs will be obtained to determine which plants are selected and preferred by the public and why. Results obtained will provide guide-lines of which plants to consider for propagation and cultivation. The distribution and availability of selected plant material for propagation will also be investigated.

This is an umbrella project consisting of several individual MSc and PhD research projects investigating the propagation and cultivation of grassland plant species. Results will be compiled into and extensive volume on the propagation of Highveld grassland plant species.

Key words: Highveld Grassland; Ornamental Horticulture species; Eco-friendly landscaping species; Medicinal plant species; propagation; cultivation

The Future African Foraging Garden; an Experiment in African Urban Agriculture and Crop Conservation

Author: Jason Sampson

PP: Pages 6-14

Focused on African Orphan Crops, the Future Africa foraging landscape is part of the ongoing collaborative project that is the rai-son d'être for the establishment of this research orientated campus. This is a short synopsis of the talk given to the IPPS Southern Africa 2020 Annual conference on the history of the FA campus gardens. Subjects dealt with include the projects trajectory from inception to completion, the philosophy and practical aspects of its design and the future prospects of the concept and collection.

Keywords:  Food crops, indigenous, orphan crops, community outreach

Year 2020 summary -The International Plant Propagators’ Society-Southern Region of North America- (SRNA) virtual meetings

Author: Brie Arthur

PP: Pages 15-21

Due to the pandemic, there was no annual meeting in 2020 of the IPPS- Southern Region of North America (SRNA). In place of the annual meeting, the SRNA successfully led, planned and executed the 3-day North American Virtual Summit (NAVS) during Oct 27-29, 2020. There was a total of a total of 947 attendees. There were three virtual presentations given by

Drs. David Creech, Dennis Werner and Mike Dirr - as well as virtual nursery tours. Nine students competed in the Charlie Parkerson Virtual Student Research Competition. Three students delivered 20-min presentations and the remaining six students gave shorter, “oral poster “presentations. The SRNA remains in good financial condition thanks to the conscientious management of Sec-Tres, Donna Foster. Dr. Gary Knox received the Meadows Award and Dr. Dave Creech was recognized as a Fellow. The SRNA currently plans to hold the 45th Annual meeting on Oct 23-26, 2021 in Mobile, Alabama.

Keywords: Annual Meeting, CoVid-19, North American Virtual Summit (NAVS), Southern Region of North America (SRNA), Parkerson Virtual Student Research Competition

Morphological and cytological characterization of six porterweed - Stachytarpheta spp. selections

Author: S. Brooks Parrish, Renjuan Qian, Sandra B. Wilson, and Zhanao Deng

PP: Pages 22-28

Porterweed (Stachytarpheta spp.), a member of the verbena family, is a common ornamental plant in warmer parts of the U.S. that is frequently used in pollinator gardens to attract many species of butterflies and hummingbirds. Much floral diversity exists within the genus and hybrid forms. This study was conducted to assess the growth habit, flowering, DNA content, and chromosome number of six porterweed selections to explore the relationship among species. Results identified three distinct porterweed growth habits (upright, semi-upright, and prostrate) and showed that nuclear DNA content ranged from 2.95 to 3.79 pg/2C. Chromosome counting revealed that all porterweed accessions tested were polyploid (tetraploid, pentaploid and hexaploid), with the exception of dwarf blue porterweed (Stachytarpheta spp.) that was darkly stained chromosomes as they become organized in the metaphase stage of cell division. Subsequent cytological and morphological comparisons can be used to not only readily distinguish invasive and non-invasive forms of porterweed, but aid in future breeding programs.

Keywords:  Chromosome, DNA content, growth habit, ploidy

Influence of substrate stratification and fertilizer placement on growth of ligustrum - Ligustrum japonicum - and germination and biomass of bittercress - Cardamine flexuosa - in containers

Author: Yuvraj Khamare, S. Christopher Marble, James E Altland and Annette Chandler

PP: Pages 29-37

Substrate stratification is a method of filling nursery containers with pine bark (or other substrates) with different particle sizes in “layers” in order to improve soil moisture dynamics. Currently, substrate stratification, or layering, is being investigated by some researchers as a method to increase the efficiency of production inputs such as irrigation and fertilization. It is typically performed using larger particle bark as the bottom substrate and finer particle bark as the top substrate to achieve more uniform moisture distribution within containers. The objective of this study was to evaluate the effect of stratified substrates and strategic fertilizer placement on the growth of common nursery weeds and ornamental crops. In contrast to typical methodology, this study evaluated use of coarse bark (screened to 1.3 or 1.9 cm) as the top substrate and finer bark (0.95 cm) as the bottom substrate with the goal of reducing water holding capacity in the top 5 to 7.5 cm of the substrate to reduce weed germination and growth. Results showed that substrate stratification significantly decreased the growth of bittercress (Cardamine flexuosa) by 85% to 90% in comparison with substrates that were not stratified. While stratification initially reduced growth of ligustrum (Ligustrum japonicum), at 6-months after potting , there was no difference in ligustrum shoot or root weight in comparison with non-stratified industry standard substrates. The results indicate that substrate composition along with strategic fertilizer placement can be utilized as an effective weed management strategy.

Keywords: Resource efficiency, weed control, weed management

Where did the water go?

Author: Brian A. Schulker, Brian E. Jackson, and William C. Fonteno

PP: Pages 38-46

pathways for water to move through, with size and shape determining the efficacy of these channels. Reduced particle size diversity can lead to excessive leachate, poor substrate hydration, and an inefficient irrigation practice. This research was designed to examine the water capture characteristics of peat, coir, and pine bark using three initial moisture contents (MC) of 67%, 50%, and 33% (by weight) through subirrigation under three time-interval pulse irrigation regimens. The objective was to determine the impact of differing irrigation event durations (5, 10, 20) over a 60-min total period of time, water depth, and initial moisture on the initial water capture rate of these three substrates. Initial capture rate (ICR) was influenced by MC, irrigation water depth, and inherent substrate characteristics (hydrophobicity / hydrophilicity). Initial moisture content had the greatest impact on peat, regardless of water depth or pulsing time. Lower moisture conditions increased the hydrophobic characteristics of peat, lessening the amount of water it was able to capture in the first irrigation event with the ICR of peat never reaching 1 mL/min at 33% MC. Pine bark had a 2 mL/min decrease in initial capture rate across 67, 50, and 33% MCs, while coir’s hydrophilic nature reduced any moisture content affects. At 50% MC or less, coir had the highest capture rate across all substrates, pulsing durations, and water depths. Water depth was found to increase capture 2-4 mL/min across all substrates (aside from 33% MC peat). While pulsing time produced variable results, with an increase in pulsing time not always equaling the added volume of water from the 5 min treatment. Ultimately, these three substrates portrayed benefits to irrigation capture that further research is needed to understand. Pine bark captured more water under low moisture equal to or better than 50% and 67% MC while coir and peat exhibited higher water retention abilities (peat at higher MCs). Engineering substrates to combine or enhance these characteristics could allow growers to decrease irrigation rates and frequencies while still producing healthy, viable crops. It is believed to be feasible to select substrate components (or types) to fit the irrigation delivery method and container type of a grower to achieve maximum irrigation efficiency for different crops.

Keywords: Capillarity, subirrigation, hydrophobicity, substrate, macropore, micropore

Evaluation of honey as a rooting aid for the propagation of Rosa ‘Red Cascade’

Author: Anthony T. Bowden, Patricia R. Knight, Christine E.H. Coker, Jenny B. Ryals, Scott A. Langlois, Shaun R. Broderick, Eugene K. Blythe, Hamidou F. Sakhanokho, and Ebrahiem M. Babiker

PP: Pages 47-51

Previous research has shown that honey may prove beneficial to the plant propagation process. The objective of this research was to evaluate whether addition of honey to water-soluble auxin solutions increased root growth and uniformity compared to auxin solutions without honey on medial cuttings of Rosa ‘Red Cascade’. The 4×5 factorial experiment consisted of four honey types (none, general multiflora, Manuka, or locally sourced honey), and five auxin levels (0, 250, 500, 750, or 1,000 ppm indole-3-butyric acid (IBA). Utilization of honey or auxin during propagation of ‘Red Cascade’ miniature rose did not increase percent rooting, number of roots, root length, shoot height, or root quality rating for cuttings. Additionally, honey type and auxin rate had no effect on net photosynthetic rate and stomatal conductance. Further research is being conducted with other woody ornamental plant species that vary in rooting difficulty to determine if addition of various honey types to water soluble IBA solutions enhances rooting responses.

Keywords:  Auxin, cutting propagation, indole-3-butyric acid (IBA)

Mulch depth effect on rooting stem cuttings and weed control during propagation

Author: Isha Poudel and Anthony Witcher

PP: Pages 52-59

Hand weeding is the most common method for controlling weeds in nursery crop propagation, but it is time-consuming and costly due to high labor costs. Pre-emergence herbicides are not labeled to be used in non-rooted cuttings, but mulches may be a viable alternative to hand weeding and herbicides. The objective of this study was to determine the effect of mulch type (coarse vermiculite, paper pellets, pine pellets and rice hulls) and mulch depth [1.3 and 2.5 cm (0.5 and 1 in.)] on rooting stem cuttings and weed control in propagation. Hydrangea softwood cuttings (Hydrangea paniculata ‘Phantom’) were used for the rooting study while seeds of two weed species [large crabgrass (Digitaria sanguinalis) and bittercress (Cardamine hirsuta)] were used for the weed control study. Rooting percentage for hydrangea was 100% for all treatments except rice hulls and paper pellets applied at 2.5 cm (1 in.) depth (90% and 95%, respectively). Root dry weight and total root length were similar to the control for all mulches. Root volume was lowest for paper pellets at 2.5 cm (1 in.) depth, but similar to the control for all other treatments. Crabgrass seedling counts were similar for all treatments compared to the non-treated control. Bittercress seedling count was lower than the non-treated control for pine pellets at both mulch depths. Pine pellets and paper pellets suppressed shoot fresh weight of crabgrass and bittercress at both mulch depths. We conclude that pine pellets and paper pellets were found to be effective in controlling weeds in propagation, but further research should focus on rooting safety of other crop species.

Keywords: Cardamine hirsuta, Digitaria sanguinalis, Hydrangea paniculata ’Phantom’,

nursery crops, weed efficacy

Green lacewing (Chrysoperla rufilabris) is a voracious predator on crapemyrtle bark scale - Acanthococcus lagerstroemiae

Author: Bin Wu, Runshi Xie, Mengmeng Gu, Hongmin Qin

PP: Pages 60-70

Crapemyrtle bark scale (CMBS, Acanthococ¬cus lagerstroemiae), an invasive sap-sucking hemipteran, has spread across 14 states of the United States. The infestation of CMBS negatively impacted the flowering of some ornamental plants, and even the fruiting of some economically important crops. Using natural enemies, a non-chemical approach, would be beneficial for the integrated management of CMBS. Eggs of the green lacewings were observed on CMBS-infested crapemyrtle plants at Texas A&M University campus. Aiming to utilize green lacewings (Chrysoperla rufilabris) as a biocontrol agent of CMBS, predatory capacity of the green lacewings on CMBS was evaluated in laboratory conditions in this study. The results confirmed that the larval green lacewings could prey upon CMBS’s nymphs, eggs, and adults. The average duration of the first egg consumption (P<0.0001) and the mean number of CMBS eggs consumed per larval green lacewing in 24 hours (P<0.0001) differed among different developmental stages. The 1st instar lacewing took 141.4 ± 4.8 sec. (mean ± SE) to consume the first CMBS egg and finished 11.8 ± 1.3 CMBS eggs in 24 hours. Whereas, the 3rd instar green lacewings devoured the first egg in 60.3 ± 3.0 seconds and consumed 176.4 ± 6.9 eggs per 24 hours. The Y-tube assay demonstrated that 78.1 ± 4.7% of larval C. rufilabris located CMBS under dark conditions. Thus, the evaluation of the predation capacity and Y-tube results confirmed that C. rufilabris could potentially be applied to control CMBS biologically.

Keywords:  Biological control, green lacewings, predatory capacity, Y-tube assay

Biological parameters of crapemyrtle bark scale (Acanthococcus lagerstromiae

Author: Runshi Xie, Bin Wu, Gary W. Knox, Mengmeng Gu, Hongmin Qin

PP: Pages 71-80

Crapemyrtle bark scale [(CMBS); Acanthococcus lagerstroemiae], an exotic pest insect in the United States, causes damage to popular crapemyrtle landscape plants - as well as other economically important or native plant species, such as pomegranate, apple, and American beautyberry. Age-stage, two-sex table study analysis was conducted to evaluate the biological parameters of CMBS on different species and cultivars of Lagerstroemia under laboratory conditions at 25C and 250 μmol m-2 s-1 light with a photoperiod of 12:12 (light: dark). Crapemyrtle bark scale development was found to be greatly influenced by plant host. This study aimed to provide important biological and ecological data of CMBS. A comprehensive life table study was conducted for the first time - in order to gain a thorough understanding of CMBS development, survival, and fecundity on different plant species and cultivars of Lagerstroemia.

Keywords:  CMBS, crapemyrtle, ecology, life table, scale insect

Effects of gibberellic acid (GA3) and cold stratification on sparkleberry (Vaccinium arboreum) germination under different collection times

Author: Ping Yu, Lin Li, Qiansheng Li and Mengmeng Gu

PP: Pages 81-86

Sparkleberry has the potential to be used as commercial blueberry’s (Vaccinium spp.) rootstock due to its wider adaptation to the environment, tolerance to higher pH, and its singular architecture, which can reduce blueberry yield loss during mechanical harvesting. There is little information in the literature on seed germination of sparkleberry. We report that gibberellic acid and cold stratification work synergistically to increase sparkleberry germination for seed collected in Texas during November and December. The optimal germination treatments for sparkleberry seeds collected from November was 500 mg L-1 gibberellic acid (GA3) followed by cold stratification for 9 weeks, which had a 70.4% emergence percentage.

Keywords:  Blueberry rootstock, seed germination

Lessons from Nature: Studies on mangrove tree biotechnology

Author: Prakash P. Kumar and Pannaga Krishnamurthy

PP: Pages 87-94

Salinity is an abiotic stress that reduces the growth and productivity of crop plants worldwide. Mangrove trees such as Avicennia officinalis exhibit remarkable ability to grow in saline environment by means of various adaptations. Such adaptations include secretion of excess salt from the leaf surface via specialized salt glands, as well as the ability to exclude ~95% salt from seawater due to enhanced hydrophobic root barriers (suberin lamellae) in their roots. Certain cytochrome P450 enzymes play a key role in biosynthesis of suberin precursors. Knowledge gained by studying mangroves can be used for biotechnological applications. Thus, we identified several CYTOCHROME P450 (CYP) genes that were induced by salt treatment in A. officinalis roots. Using appropriate Arabidopsis mutants, such as atcyp94b1, we characterized the function of CYP94B1 gene in regulating suberin biosynthesis. The atcyp94b1 mutant seedlings showed salt sensitivity with reduction in root elongation. When treated with salt, their roots exhibited reduced suberin lamellae and Casparian bands. Heterologous expression of the coding sequence of A. officinalis CYP94B1 in atcyp94b1 resulted in rescuing of the salt sensitive phenotypes, indicating the involvement of CYP94B1 enzyme in suberin biosynthesis. Additionally, we have expressed selected genes from the mangrove in rice, and the transgenic rice plants acquired higher salinity tolerance. These findings opened up additional strategies for salinity tolerant crop plants in the future. Our current efforts in these projects will be discussed.

Keywords: Avicennia, CYTOCHROME P450, salinity, roots, ecology suberin, salt glands