2017 ASHS Annual Conference

Small anise tree is a native evergreen shrub used in southeastern U.S. landscapes due to its adaptive nature to a range of environmental conditions and dense hedge-forming ability. There are very few cultivars on the ornamental market and little natural phenotypic variation exists. Traditional breeding is difficult due to very low seed set, as well as different timing of receptivity of reproductive structures. This project utilized a relatively common method of mutation breeding, gamma radiation, in an attempt to induce variation and improve growth characteristics of Illicium parviflorum. The purpose of these studies were 1) to determine if gamma radiation leads to stable variation(s) of the species and 2) to determine the optimal timing of cuttings and rates of radiation application (Gy). In 2016 vegetative cuttings were taken at three growth stages: hardwood, semi-hardwood and soft/actively growing wood. Effect of radiation rate was evaluated on hardwood cuttings on 16 Feb. treated with 20, 40 and 60 Gy, semi-hardwood cuttings on 4 Aug. at 3, 5, 10, 20, and 40 Gy; and on softwood on 20 May at 5, 10, 20, 40, and 60 Gy using a Cobalt⁶⁰ source. An untreated control was included at each date. Percentage of cuttings rooted under mist was recorded after nine to 12 weeks. Preliminary results indicated an optimal rate and period of 5 Gy in August, which yielded 90% rooting, 10% lower than the untreated control. In February, control plants only had a rooting percentage of 60% and no plants treated with radiation rooted. Survival of rooted cuttings decreased dramatically above 5 Gy. Rooted cuttings treated with radiation will be evaluated for differences compared to untreated controls. The experiment is being repeated in 2017 and a large number of cuttings will be irradiated in early August to maximize the potential of inducing variation via gamma radiation.