Optimization of adventitious rooting of hazelnut stem cuttings to expedite on-farm commercialization trials

Optimization of adventitious rooting of hazelnut stem cuttings to expedite on-farm commercialization trials

Summary

The purpose of this project is to improve bud retention, increase vegetative growth and long term survival of softwood and semi-hardwood hazelnut cuttings. Softwood cuttings were taken from three different genotypes, H3R11P52, OSU 408.040, and OSU 541.147. Several plant growth regulators were applied over an 8-week period, but none of the foliar treatments significantly improved bud retention or vegetative growth in any of the genotypes. A significant difference in bud retention was found among the different cultivars though, where both H3R11P52 and OSU 408.040 retained significantly more buds after 8 weeks than OSU 541.147. Only two genotypes (OSU 541.147 and ‘Ratoli’) were used in the semi-hardwood cutting experiment. Similarly, none of the treatments resulted in higher bud retention than the control, but a difference in bud retention was found between genotypes where ‘Ratoli’ had a significantly higher percentage of live buds after 8 weeks than OSU 541.147. Although thus far we have not found a treatment that significantly increases bud retention and long term survival in softwood or semi-hardwood hazelnut cuttings, we have corroborated previous findings that the genotype has a significant effect on hazelnut cutting survival rates.

Objectives/Performance Targets

The goal of the project is to optimize the rooting and survival of both semi-hardwood and softwood hazelnut stem cuttings as a more efficient and cost-effective method of clonal hazelnut propagation. The following were the objectives, followed by current progress on the objectives.

1. 1. Measure the effectiveness and optimize the ethylene inhibitor (1-MCP) method in Contessa et al. (2011) of inducing bud retention of semi-hardwood hazelnut cuttings taken at different dates.                                                            A second year of data has been obtained for this portion of the experiment. This year cuttings were taken at one time point, because an additional ethylene inhibitor aminoethoyxvinylglycine (AVG) was added to the experiment. AVG was tested on the cuttings at three concentrations (150, 500 and 750ppm).

1. 1.  The effectiveness of the foliar formulation of 1-MCP was to be compared with the wettable release (gas) formulation, for efficacy in the prevention of bud abscission, survival and subsequent shoot growth of semi-hardwood hazelnut cuttings.                                                                                                                             This aspect of the experiment was performed for a second year and compared to an additional ethylene inhibitor described above.

1. 1. To investigate and optimize the application of ethylene inhibitors and gibberellic acid on bud retention, shoot growth and overall survival of softwood hazelnut cuttings.                                                                                           Data for this portion of the experiment was collected this year, a total of 6 treatments were applied including one (water) control treatment. The remaining treatments as shown in the supplemental Figures 1 and 2 were combinations of GA3, GA4,7 and 6-BAP, which were all chosen to enhance bud retention and shoot growth.

Accomplishments/Milestones

In Mid-June of 2014 semi-hardwood cuttings of three genotypes (OSU 408.040, OSU 541.147, and H3R11P52), were collected, dipped in 1000 ppm Dip-N-Grow then stuck in rooting benches. At 2 weeks, 4 weeks and 6 weeks after the collection date the cuttings were sprayed with the following treatments: water (control), 125 ppm foliar fertilizer, 50 ppm GA 4,7, 50 ppm GA3 + 10 ppm 6-BAP, 50 ppm GA 4,7 + 10 ppm 6-BAP, 50 ppm GA3. At 8 weeks after collection the cuttings were dug up and assessed for number of live buds, number of roots (expressed as a root rating 1-5), and number of new leaves.

            Very few new leaves had grown in any of the cuttings after 8 weeks, but a number of cuttings did show live buds and significant root growth. The treatment effects on bud retention and rooting can be visualized in Figures 1 and 2 respectively. The water, foliar fertilizer treatment, and GA4,7 + 6-BAP treatment did not result in significantly different bud retention but all three showed significantly higher bud retention than any other treatment.

            Although all cuttings received the same rooting compound application prior to sticking, the root growth was negatively affected by application of the foliar products in this study. There was a significantly lower root rating in cuttings treated with any compound except for foliar fertilizer which had a similar rooting response to the cuttings treated with water.

            There was also a significant difference in genotype response where H3R11P52 had significantly higher bud retention than OSU 541.147 and higher rooting response than either of the other cultivars.

            There was no significant genotype by treatment interaction in bud retention or rooting in this experiment.

At the end of September 2014, semi-hardwood cuttings were taken from two genotypes (‘Ratoli’ and OSU 541.147) and dipped in 500 ppm IBA salt and stuck in rooting benches (rooting media consisted of 2 parts perlite: 1 part peat). Foliar treatments were applied to the cuttings immediately after they were stuck (except the cuttings treated with gaseous 1-MCP). The rooting hormone was changed from last year’s experiment because of a much higher rooting success in cuttings treated with 500 ppm IBA, in a small-scale, preliminary softwood cutting experiment earlier in the year (data not shown). The cuttings were monitored closely over an 8 week period for bud retention, and at 8 weeks the cuttings were dug up and the number of live buds, dead buds, young leaves and roots were recorded.

After 8 weeks many cuttings were still alive but none of the cuttings showed root growth. The cuttings showed various degrees of live bud retention though. Equally significant high bud retention was observed in cuttings treated with three different compounds; control cuttings treated with water in the gas chamber, 500 ppb 1-MCP in the gas chamber, and 1.5 ppm 1-MCP liquid. The highest average percentage of live buds was 82% found in the cuttings placed with water in the gas chamber.

            There was a significantly higher percentage of bud retention for ‘Ratoli’ (85%) than OSU 541.147 (52%).

            There was no significant genotype by treatment interaction on live bud retention in this experiment.

• Supplemental Data Figures

Impacts and Contributions/Outcomes

The initial results from the experiments this year showed a significant effect of genotype on bud retention and rooting in both softwood and semi-hardwood hazelnut cuttings. This could result in a greater challenge in finding a compound to enhance shoot growth and bud retention on a wide range of cultivars. It shows the need to increase the breath of cultivars included in future experiments in order to ensure these plant growth regulators are effective across a wide range of genotypes.

            Rooting issues in these experiments could also be a result of the different genotypes we have used in these studies in comparison to other hazelnut propagation studies, which have resulted in greater rooting percentages. Poor rooting could be confounding the treatment effects of bud retention and shoot growth, thus a future focus in these hazelnut cutting experiments will be to find a more effective rooting compound for cultivars native to the North East region of the United States. While our progress to date has been disappointing, efforts will continue in 2015 to explore several other options to improve rooting, bud retention, and survival of hazelnut stem cuttings. This will include exploring in more detail the factors of timing of cutting collection, location of cuttings within the canopy of the tree, and a wider range of rooting hormones, temperature, fertility, and light treatments.

Collaborators: