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 promote long term survival of softwood and semi-hardwood hazelnut cuttings. This past year softwood cuttings were taken from 14 cultivars and breeding selections and were used in two similarly designed experiments. Both experiments were organized into factorial treatment structures where treatments included different media types, hormone concentrations, and the use of different hazelnut tissues (basal shoots or canopy stems). Results corroborated previous findings that different genotypes lead to differential cutting success, but also showed that tissue type used for propagation has a significant effect on cutting survival. Specifically stem tissue from both basal and canopy stems lead to greater cutting success than apical shoot cuttings. These results will be used in the development of future propagation experiments in the hopes of developing a more robust hazelnut cutting propagation method.

Objectives/Performance Targets

The goal of the project is to optimize the rooting and survival of both semi-hardwood and softwood hazelnut stem cuttings, which would present a more efficient and cost-effective method of clonal hazelnut propagation then that currently available. The objectives of the project are listed below followed by my current progress.

1. 1. Measure the effectiveness and optimize the ethylene inhibitor (1-MCP) method described in Contessa et al. (2011) for enhancing bud retention of semi-hardwood hazelnut cuttings taken at different dates.                                                                                                                                 The 2013 and 2014 semi-hardwood cutting experiments yielded poor rooting and subsequent bud retention results. Thus, we will be assessing ethylene inhibitor compounds on dormant hardwood cuttings this winter as an alternative to semi-hardwood cuttings with the similar goal of enhancing bud retention, survival, and subsequent shoot growth of cuttings.

1. 1.  The effectiveness of the foliar formulation of 1-MCP was to be compared with the wettable release (gas) formulation for its efficacy in the prevention of bud abscission and as an aid to survival and subsequent shoot growth of semi-hardwood hazelnut cuttings.                                                                                                                 As stated with objective 1, I will be assessing hardwood dormant cuttings this winter as an alternative to semi-hardwood cuttings.

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.

Our previous attempts to propagate softwood cuttings have resulted in very little root growth. To improve upon previous attempts, this past year I established two factorial experiments exploring several different methods of softwood cutting propagation to find optimal conditions for root initiation and growth. Since our previous results have shown significant differences in root and shoot growth of cuttings among cultivars, we included 14 cultivars in our experiment design to ensure we find an optimal propagation method across many hazelnut varieties. In addition, I investigated the effect of media, rooting hormone concentration, and tissue type on propagation success of the cuttings.

Accomplishments/Milestones

Two softwood cutting experiments were established with slightly different treatment structures. The following growing conditions were investigated: growing media, rooting hormone concentrations, and developmental tissue stage. The following is a description of the new treatments and why they were chosen:

Growing Media: Oasis rooting cubes were compared to standard propagation media (a mixture of 1 part ProMix to 1 part pearlite). Oasis cubes are synthetic polyurethane based foam that contain micronutrients and are purported to allow for better aeration than standard peat based media. In addition to potentially higher rooting success, foam cubes are easier to handle and prepare, and their use can lessen the damage to roots when transplanting. My decision to include foam rooting cubes in the experimental design was based in part on a previous study that showed foam cubes increase cutting success in semi-hardwood peach cuttings (Avery and Beyl, 1991).

Hormone concentrations: In a small unpublished study we noted that Dip-N-Grow rooting hormone (a mixture of IBA and NAA) was most effective in inducing root growth in hazelnuts. In our softwood cutting experiments we used Dip-N-Grow at two rates a 1:20 dilution (500 ppm IBA+ 250 ppm NAA) and a 1:15 dilution (750 ppm IBA + 375 ppm NAA). These rates were similar to suggested (Dip-N-Grow) rooting concentrations for semi-hardwood cuttings.

Tissue Type: There are four main tissue types to use as cuttings for propagation in hazelnuts, canopy shoot cutting tissue, which consists of stem cuttings and apical tip cuttings, and sucker or basal hazelnut tissue, which also consist of stem cuttings and apical tip cuttings. Both apical and stem shoot tissue, along with stem basal cutting tissue were used in the factorial treatment design. Tip cuttings from basal tissue were not utilized due to the short internode length.

Experiment 1: The experiment was set up as a 14x2x2x2 factorial design. Cuttings were taken in June of 2015 from the following 14 hazelnut cultivars, which are considered the first factor in the design (cultivars: Jefferson, and Yamhill; Oregon State University breeding selections: OSU 859.050, OSU 859.053 and OSU 859.086; Rutgers University breeding selections: CR11P10, CR12P35, CR4P43, H3R12P62, H3R4P23, CR11P7, CR6P56, H3R7P25, and CR7P58). The following factors were also included: developmental tissue type (canopy shoot stem tissue or shoot apical tissue), rooting hormone treatment (Dip-N-Grow rooting treatment at either a 1:15 dilution or 1:20 dilution), and media type (Oasis rooting cubes or 1:1 Promix to pearlite packed in a propagation bench).

Experiment 2: The experiment was set up as a 10x3x2x2 factorial design. Cuttings were taken in June of 2015 from the following 10 hazelnut cultivars, which are considered the first factor in the design (Jefferson and Yamhill; Oregon State University breeding selections: OSU859.050, and OSU 859.086; Rutgers University breeding selections: CR11P10, CR4P43, CR11P7, CR6P56, H3R7P25, and CR7P58). The following factors were also included: developmental tissue type (shoot stem, shoot apical and basal stem tissue), rooting hormone treatment (Dip-N-Grow rooting treatment at either a 1:15 dilution or 1:20 dilution), media type (oasis rooting cubes or a 1:1 promix: pearlite media mix in rootmaker flats (11 cu in. cells)).

The following rating scale was used to assess the health of each cutting: 0= dead, 1= dead tip but the remainder of the cutting is alive, 2= buds are retained and the overall health of the cutting is good, and 3= bud break has occurred and the cutting is growing new shoots/leaves. This scale was used to rate the cuttings at 3, 8 and 11 weeks after being stuck in the benches. The data was recorded then analyzed using SAS 9.4.

This winter I will be working to take dormant hardwood hazelnut cuttings and use similar rooting treatments along with bud retention treatments described in the objectives.

Avery, J. D. and Beyl, C. B. 1991. Propagation of Peach Cuttings Using Foam Cubes. Hortscience. 26(9).

Impacts and Contributions/Outcomes

Although my study did not result in the propagation success we had hoped for, it did lead to findings that will help provide a foundation to improve hazelnut propagation techniques in the future. This past summer two experiments were performed on softwood hazelnut cuttings with slightly different treatment structures that showed similar results.

The most striking result was that up until 11 weeks after sticking the cuttings, most cuttings were healthy. After 11 weeks in the benches, however, the majority of cuttings across all cultivars died. This can be visualized in histograms of both experiments over time (Supplemental Figures). We hypothesize that the sudden death of many cuttings could have been due to overheating of the greenhouse in August.

Despite the death of many cuttings after 11 weeks in the propagation benches, we were able to report positive effects on rooting due to other treatments. In terms of the developmental stage of tissue that is best suited for softwood cutting propagation, stem cuttings off of hazelnut canopy shoots yielded a greater number of healthy hazelnut cuttings than when apical tips of the same shoots were used. Although, in the second experiment basal (sucker) cuttings were included and yielded a greater percentage of successful cuttings than stem cuttings of shoots across cultivars. Rooting media also showed positive, albeit variable, results from cultivar to cultivar, where the foam cubes generally led to equal or greater cutting health/success than the 1:1 promix to perlite media in either large propagation benches or rootmaker flats. The hormone concentrations used had similar effects on all cultivars, and we were unable to discern improvements in rooting due to one hormone concentration over another.

We are refraining from reporting any results to growers until we have found a more robust method of propagating hazelnut cuttings, but we feel that the findings from these studies will help us to develop more successful experiments in the future. Although there was high cutting mortality in both experiments, we have found stem cuttings lead to greater propagation success. Thus we will begin to focus on using stem cuttings off of basal branches in further experiments.

• Histograms of the results of both Experiment 1 and 2

Collaborators: