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 the project is to develop a more cost-effective, efficient, and sustainable method of propagating new hazelnut cultivars. The specific goal is to improve the success rate of propagating hazelnuts by semi-hardwood and softwood stem cuttings through the use of novel ethylene blockers as well as the application of gibberellic acid and cytokinins. The first two sets of semi-hardwood cutting experiments have been completed and data has been collected on survival rate, percent bud and leaf retention, and root growth. Results show that cutting survival rates were below 10%, which can be explained in part by a serious mechanical failure of the mist system at one point during the study. The bud retention was as high as 57% in the Rutgers breeding selection H3R11P55; however, overall leaf retention and root growth were low, which explains the poor 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.        

          I have obtained preliminary results for this work, but due to technical difficulties (inconsistent misting of benches), I was unable to accurately compare how the date cuttings are taken affects cutting survival rates. The mist benches were shut down inadvertently over one hot weekend in October with no mist applied for a 24 h period. This caused severe leaf burn on both experiments (September 16/17 and September 30/October 1 initiation dates), which lead to subsequent leaf drop on almost all of the cuttings. Those cuttings that dropped their leaves generally did not develop roots (the 10% than retained their leaves rooted at a much higher percentage).

        The first round of treatments have been performed, and no significant treatment effect on bud retention has been shown. See the discussion in Objective 1, which I believe is a major factor for why I was not able to discern any differences.

This objective has not yet been addressed, but will be this upcoming year with the softwood cuttings. This experiment will start in May 2014.

Accomplishments/Milestones

            Only the first round of semi-hardwood hazelnut cuttings have been taken to date. The following breeding selections were chosen to take semi-hardwood cuttings from: Rutgers H3R11P55 and H3R11P52 and Oregon State University (OSU) 408.040 and 541.147. Although they were not initially proposed to be included, the OSU selections were added to the study because they are also promising cultivars for production in the northeast and ample stem tissue was available for developing the factorial experiment. The first round of cuttings was taken on September 16 and 17, and subsequently stuck on one propagation bench in a randomized complete block design. They were given their designated 1-MCP treatments and all were dipped in Hormodin #3 IBA .8%, immediately before being stuck into the benches. The second round of cuttings were taken on September 30 and October 1, and also stuck in a randomized complete block design on a separate bench.

            Each round of cuttings was kept in their benches for ~10 weeks. During this time there were a few mechanical issues with the misting system that were beyond our control, and as a result parts of the benches were dry for extended periods of time. These periods of dryness caused premature leaf drop in many of the cuttings (especially on the second round). The misting system has been repaired and will be monitored more closely for the next round of cuttings.

            After ~10 weeks the cuttings were taken out of their benches and analyzed for the number of live buds, dead buds, leaves, roots, and individual root length and width. Due to the very low overall rooting percentage (<10%) (which we suspect was due to the misting issues), all rooted cuttings were saved and none were destructively sampled.

            Preliminary, although possibly confounded, results indicate that there is no significant treatment effect on bud retention (cutting survival) based on the various treatments they were exposed too. However, there was a significant cultivar effect on bud retention. The results indicate that OSU 541.147 has a significantly lower percentage of bud retention in all treatments (8.2% for the first round of cuttings, and 3.8% for the second round of cuttings (P < .0001). The remaining cultivars all showed significantly higher (but similar) bud retention rates than OSU 541.147. The first round of cuttings showed an overall 7% survival rate, and the second round of cuttings showed a 1% survival rate. Despite the low survival rate, there seems to be a weak correlation between the number of leaves retained after 10 weeks and the number of roots formed after 10 weeks (the correlation coefficient was r=.5, where 0 indicates the variables are not correlated and 1 shows a high level of correlation). Given this correlation, drought factors beyond our control (causing early leaf drop), could explain the poor root growth and subsequent cutting survival.

            The next step in the project is to take softwood hazelnut cuttings in the spring (May 2014) and use 1-MCP to promote bud retention as well as to test combinations of gibberillic acid and cytokinins to promote a flush of shoot growth sufficient to keep the cuttings alive through next winter. Once the softwood cuttings are taken out of their rooting benches and analyzed, the next set of semi-hardwood cuttings will be taken and grown with no drought stress to determine if 1-MCP has a treatment effect.

Impacts and Contributions/Outcomes

The preliminary results indicate that there is a significant correlation between cutting success (indicated through bud retention) and genotype. Our preliminary results suggest that treatment of cuttings with 1-MCP has no effect on bud retention and ultimately no effect on overall cutting success. It was already known that drought stress can negatively impact cutting success, but our findings show that hazelnut cuttings are particularly drought intolerant despite treatment with 1-MCP (as evidence by the low survival rate of the cuttings <10%).   Lastly leaf retention seems to be correlated to rooting success, which further corroborates how critical it is for hazelnut cuttings to retain leaves (avoid drought stress) for as long as possible to help induce root growth. These results are all important in developing factsheets and guidelines for nurserymen propagating hazelnuts. The current results are preliminary, and confounded by issues with the intermittent mist system. However, after further analysis, and additional rooting data (six more cutting dates will be examined), we should be able to develop a better understanding of the process. From this, we hope to develop useful guidelines on implementing a more cost-effective means of propagating hazelnuts.

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