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Cannabis sativa L. (hemp) develops plants with either male or female flowers, and growers of hemp greatly prefer female flowers which bear the glandular trichomes that contain cannabinoids. Feminized (all female) seeds are highly desired, which are produced by crossing a female plant with a masculinized female plant. Masculinization is achieved through the inhibition of ethylene and/or addition of gibberellins before flower initiation in female plants. The hemp industry uses silver thiosulfate (STS) to masculinize hemp, but spraying silver poses environmental concerns. This study compared STS to three other ethylene-inhibiting agents: aminoethoxyvinylglycine (AVG), cobalt nitrate (CBN), and 1-methylcyclopropene (1-MCP). Treatments of STS and CBN also included gibberellic acid as a synergist. Plants treated with STS exhibited superior masculinization and pollen dispersal compared to plants treated with AVG, CBN or 1-MCP. Only plants treated with STS or AVG produced pollen in sufficient quantities for collection. This pollen was assayed for germination potential initially and after storage for up to five weeks at 22.2, 7.2, or 1.1°C. Pollen from plants treated with AVG remained viable for four weeks at 1.1°C, whereas STS-treated plants produced pollen that was viable for three weeks at 1.1°C. Due to phytotoxicity problems with AVG, STS remains the best treatment to masculinize female hemp plants when breeding for feminized seeds. In a separate study, flower tissues of hemp had considerably higher total cannabinoid concentrations compared to leaf tissues but significantly lower ratios of cannabidivarin (CBDV) to cannabidiol (CBD). To reduce variability, at least 1 g samples of fresh leaf or flower tissue should be extracted with 10 mL of methanol. Rapid throughput testing of cannabinoids as part of a breeding program should use flower tissue, preferably at the time typical of harvest.

ABSTRACT A Comparative Study of Three Growing Media and Four Plant Groups Under Extensive Green Roof Conditions in San Luis Obispo, California Todd A. Nelson Green roof growing media and plant species are critical factors when deciding on the best materials for a project. Growing media must be chosen in accordance with load bearing capacities of structures and water requirements of the plant material. Plant species must be able to thrive in the climate of the green roof and withstand a green roof’s harsh environment. The objectives of this research were: (1) to determine which of three extensive green roof growing media support the most growth of Sedum, a proven extensive green roof plant genus; and (2) to determine which of four plant groups provides the most media coverage under extensive green roof conditions. Sedum growing in a granular growing media blend with higher organic matter and larger particles provided more coverage than Sedum growing in a medium with smaller particles with lower organic matter and an experimental foam medium. Sedges covered the soil faster than Sedum, grasses, and Mediterranean species. These results will help green roof designers and landscape architects anticipate the plant growth rates during the first 36 weeks of new projects and choose more effective growing media blends. They can also observe the growth patterns of the plant groups to choose plant material that will achieve the functional objectives of a green roof more efficiently. These results are applicable to green roofs designed for moderate California coastal climates and regions with similar weather conditions.

Buffalograss [Buchloe dactyloides (Nutt.) Engelm.] is a warm season, perennial grass native to the Great Plains from southern Canada to Mexico (Beetle, 1950). This newly developed, low input, turf-type grass is recommended for use on low maintenance sites (Falkenberg-Borland and Butler, 1982; Pozarnsky, 1983; Wu and Harivandi, 1989; Shearman et al., 2005). Recently, the use of buffalograss as a turfgrass has increased due to its drought tolerance, low nutrient requirements, and low growing height (Harivandi and Wu, 1995; Frank et al., 2004). It is an excellent choice in California where water use is limited. Unsightly winter dormancy of buffalograss can be overcome by growing mixtures of buffalograss and fine fescue (Festuca spp.). Overtime species composition can be overtaken by the fine fescue, unintentionally converting the mixed turfgrass stand to a fine fescue monostand (Severmutlu, et al., 2005). Research on buffalograss establishment in fine leaved fescues from seed or by vegetative methods was completed from 2007 to 2009 at the California Polytechnic State University Horticulture Unit in San Luis Obispo, California. Comparisons were made between mixtures of eight cultivars of buffalograss (Prairie, Prestige, UC Verde, 609, Bowie, Cody, Texoka, and Bison) and three fine leaved fescue species [hard fescue (Festuca trachyphylla Thuill.), sheep fescue (Festuca ovina L), and red fescue (Festuca rubra L.)] to determine which combination and establishment strategy provides the highest quality turf for the California central coast region. Evaluations made on buffalograss establishment and competitive ability when grown in pre-existing fine fescue turfgrasses showed seeded cultivars (Bowie, Cody, Texoka, and Bison) were unsuccessfully established (zero percent coverage in two growing seasons), and vegetative cultivar (Prairie, Prestige, 609 and UC Verde) establishment was greatly dependent on the type of cultivar planted. After two growing seasons, buffalograss cultivar UC Verde had the highest establishment rate (38.6 percent living ground cover) and Prestige had the lowest (11.4 percent living ground cover). Results from this study do not recommend establishing seeded buffalograss cultivars into pre-existing fine leaved fescue turfgrass stands. Vegetative buffalograss cultivars can be established into pre-existing fine leaved fescue turfgrass stands; however, this process is too slow for most turfgrass practitioners and is quite unsightly in winter dormancy during the establishment process.

Botrytis bunch rot, caused by Botrytis cinerea, is a fungal disease that primarily affects the fruit of wine grapes. Infection of fruit consequently results in reduced yields and wine quality. These factors lead to significant economic losses for growers which prompts the implementation of management practices to control the disease. One objective of this study was to evaluate the level of resistance that populations of B. cinerea in the Central Coast region showed to various chemicals. A fungicide assay was conducted to determine resistant phenotypes to six fungicide active ingredients (pyrimethanil, iprodione, fenhexamid, fludioxonil, trifloxystrobin, boscalid). Thirty-five (2020) and 88 (2021) B. cinerea isolates were collected from Santa Maria, Cambria, Paso Robles, and Edna Valley in California and screened for resistance. The frequencies of populations (2020, 2021) showing resistance to each active ingredient were: pyrimethanil (94.3%, 81.8%), trifloxystrobin (97.1%, 100%), boscalid (77.1%, 77.3%), fenhexamid (8.6%, 25%). The majority of isolates were sensitive to iprodione (100%, 100%), fludioxonil (100%, 100%), fenhexamid (88.6%, 75%), and boscalid (22.9%, 22.7%). These results documented the accumulation of resistance in B. cinerea to various fungicides commonly used for Botrytis bunch rot management in California’s Central Coast. Another objective of this study was to determine the effective concentration of the six fungicides that reduces mycelial growth of the fungus by 50% (EC50). Seven B. cinerea isolates in 2020 and ten isolates in 2021 were selected and subjected to a sensitivity screening with serial dilutions of the different fungicide active ingredients. The fungicides found to have the highest EC50 values indicating reduced efficacy for inhibiting B. cinerea growth were Scala® (FRAC 9), Flint® (FRAC 11), and Endura® (FRAC 7). The fungicides found to have the lowest EC50 values indicating higher efficacy for inhibiting B. cinerea growth were Scholar® (FRAC 12) and Rovral® (FRAC 2). The results from this study provided information regarding the accumulated resistance of B. cinerea populations to certain chemical groups and therefore the efficacy of different fungicide active ingredients. This information can be utilized by growers as a tool to enhance and develop fungicide spray programs that effectively manage Botrytis bunch rot in Central Coast vineyards.

Fruit split is the most important physiological disorder in pomegranate production, causing devastating crop losses worldwide. Foliar nutrient applications have been used experimentally to mitigate pomegranate fruit split but none have been conducted using the industry standard cultivar, Wonderful, and little is known about the effects of foliar nutrient applications on pomegranate. Additionally, investigations into putative health benefits of pomegranate fruit have increased interest in its production but limited evidence exists regarding effects of agricultural practices such as foliar fertilizer applications on internal fruit quality. ‘Wonderful’ pomegranate trees at 2 commercial orchards were treated with foliar applications of ZnSO4 (3000 mg∙L-1, 4000 mg∙L-1, or 5000 mg∙L-1), MgSO4 (1%, 2%, or 3%), KNO3 (1%, 2%, or 3%), or deionized (DI) water (control). Fruit were analyzed for fruit split incidence, yield, fruit number per tree, fruit diameter, fruit mass, mass of all arils in fruit, mass of 100 arils, total soluble solids (TSS), titratable acidity (TA), antioxidant activity (AA), total phenolics (TP), and mineral nutrient concentrations of leaves and fruit. Foliar applications of MgSO4 and ZnSO4 resulted in significantly lower fruit split incidence. Treatments had no significant effect on fruit number per tree, fruit diameter, and mass, mass of all arils in fruit, or mass of 100 arils. Leaf N, K, S, Mn, and Zn were significantly affected by the treatments. TSS and TA were not affected significantly by treatments. AA ranged from 77.8-84.3 percent inhibition of 2,2’-diphenyl-1-picrylhydrazyl and TP ranged from 2489-3046 mg·L-1 gallic acid equivalents, with some KNO3 treatments significantly affecting these parameters. Fruit mineral nutrient concentrations were characterized and Zn-treated trees had greater fruit Zn concentrations. The results suggest that foliar ZnSO4 or MgSO4 could be used to decrease fruit split incidence and increase nutritional content of ‘Wonderful’ pomegranate and any of the three tested foliar nutrients could be applied as a foliar fertilizer without negatively impacting fruit yield, size, internal quality, bioactivity, or mineral nutrient concentration.

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