James E. Faust

Evaluating a Novel Method to Introduce a Mycorrhizal-like Fungus, Piriformospora indica, via an Inoculated Rooting Substrate to Improve Adventitious Root Formation

The mycorrhizal-like fungus Piriformospora indica has demonstrated potential to enhance adventitious root formation (ARF) and increase root weight when applied to the propagation substrate of unrooted cuttings (URCs). Experiments were conducted to determine the effect of P. indica on ARF of six floriculture species: cape daisy (Osteospermum ·hybrida ‘Side Show White’), crossandra (Crossandra infundibuliformis ‘Orange Marmalade’), dahlia (Dahlia ·hybrida ‘Dahlietta Margaret’), lantana (Lantana camara ‘Lucky Yellow’), poinsettia (Euphorbia pulcherrima ‘Champion Fire’, ‘Premium White’, and ‘Supreme Bright Red’), and scaevola (Scaevola aemula ‘Fan Dancer’). The treatments consisted of a peat-based growing medium that contained 5%, 10%, 20%, or 30% perlite colonized with P. indica (volume of colonized perlite/volume of growingmedium). Inoculationwith 10% to 20% colonized perlite significantly increased the root fresh weight for one cultivar, Supreme Bright Red poinsettia, whereas the 20% colonized perlite treatment resulted in a decrease in root fresh weight of scaevola and cape daisy. Rooting percentage of ‘Champion Fire’ poinsettia and dahlia showed a benefit at specific P. indica treatments, whereas cape daisy displayed a decrease in rooting percentage. Conventional rooting hormone treatment showed beneficial responses for dahlia, and ‘Champion Fire’ poinsettia rooting percentage and a negative response on lantana root fresh weight. This project demonstrates a novel method for delivering a root endophyte toURCs for the purpose of increasing ARF, and the results suggest the potential for P. indica usage for ARF enhancement. However, the results were not consistently beneficial across the eight cultivars tested, so growers would need to conduct in-house trials to identify the best treatments across a range of crop species and cultivars.

Identifying the storage potential of unrooted shoot-tip cuttings of eight ornamental species.

Unrooted cuttings are typically produced in tropical climates and shipped via air freight to North American and European markets. Shipments usually occur during 3 to 4 days per week, since customers do not desire to receive cuttings on Friday, Saturday or Sunday. Thus, the number of days per week to actually harvest cuttings is limited unless those cuttings can be held in storage prior to shipment. The objective of this project was to identify the storage potential of the following eight ornamental species: Artemisia × hybrida, Angelonia angustifolia, Diascia × hybrida, Gaura lindheimeri, Ipomea batatas, Nemesia × hybrida, Solenostemon scutellarioides and Verbena × hybrida. Cuttings were harvested from stock plants and placed at 0, 5, 10, 15 or 20°C for 2, 4, 6 or 8 days and then placed into a simulated shipping environment for two days. A control group of cuttings was not stored and only received the simulated shipping treatment. Roots and shoots were visually rated after three weeks in propagation. Angelonia and Solenstemon were the least cold tolerant species, e.g., they had damaged tissue after 2 days storage at 0°C. Angelonia, Diascia, Gaura and Nemesia were the least heat tolerant species, e.g., they did not perform well in propagation following for more than 2 days of storage at 20°C. While the optimal temperature varied from 5 to 15°C for each species, all species performed well at this temperature range following 2 to 4 days of storage. This work suggests that cutting suppliers can harvest cuttings every day of the week and ship the cuttings only 1 to 2 days per week. This creates the opportunity for companies to minimize the number of trained cutters that need to be employed and to minimize transportation costs by consolidating orders harvested throughout the week into a minimum number of shipments.