Grafting Apple Trees

Grafting Apple Trees

Whip Graft 

Apple harvest

http://pixabay.com/en/harvest-apple-ripe-red-59921/

Apple trees, or Malus domestica, are deciduous trees and are among the oldest and most widely grown fruit crops in the world. The apple tree originated in Central Asia, and was one of the first tree fruits cultivated. Apple trees can now be found throughout the northern hemisphere. Today there are over 7,000 cultivars of apples. Apples can be used for cooking and making ciders as well as simply eaten. The United States is the second largest producer of apples, making their propagation important in the agricultural industry. 

Apples can be propagated many ways including by seed, layering, cuttings, grafting and micropropagation. The vast majority of domesticated apple trees are grafted. Domesticated apple trees produce seeds that differ from the parent plants, which means domesticated apple trees much be vegetatively propagated, either by grafting or budding.

Grafting is commonly used in apple orchards because it can be done for propagation purposes, creating a new variety or repairing damage. For apple farmers, grafting to certain rootstocks is desirable because certain rootstocks are adapted to distinct environments, are resistant to specific diseases and can decrease the size of the tree, making the tree a more ideal height for harvesting. Another perk of grafting, you will see results more quickly than you would with cuttings and micropropagation. The advantage grafting has over budding is that grafting is done during the apple tree’s dormant months, whereas budding is done during the active growing period which is also a very busy time for farmers. 

Apple Tree

 http://commons.wikimedia.org/wiki/File:Apple_tree,_Fryšták_(1).jpg

Many farmers graft the variety honey crisp to differing rootstocks. Since their introduction in the 1990’s, honey crisps have quickly become one of the most popular apple cultivars due to their sweet flavor. The high demand of honey crisps along with their higher market price creates an incentive for farmers to graft honey crisp scions to rootstocks of older and less popular varieties.  

Whip graft and machine grafting are the most commonly uses methods of grafting today. A whip graft, also known as a splice graft, is a relatively simple grafting method. Here, I’ll go into detail on how to graft an apple tree using the whip graft. 

Having the correct materials for propagation is essential. Materials needed for grafting an apple tree with a whip graft are rootstock, scion, sharp and sterile knife, budding rubber strips or grafting tape, grafting seal or wax (optional), container and media. 

The first step to grafting success is selecting quality materials for your scion and rootstock. Collect your materials when the apple trees are dormant, which is during the winter months. The materials gathered need to be of current season growth. Branches must be relatively small, no bigger than 1/2 an inch in diameter. The plant used for the scion and the rootstock must be very similar in size for a successful graft. 

Grafting is done during the winter or early spring in a greenhouse environment. If your plant materials are gathered prior to the actual grafting process, make sure to store the materials properly. They should be kept in cool temperatures with moist towels on the cut area to prevent desiccation. I recommend gathering your scion and preparing your rootstock at the same time you wish to complete the grafting. 

How to cut material for whip graft

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The scion and root stock are cut with the same angle and length. Look at the figure to the left for a good visual on how the cuttings should look. The angle should be approximately 45 degrees, and the cut will be go through the entire stem. Your rootstock will be planted in a container already, so just be sure water the media well beforehand to prevent unnecessary stress for the plant. You should sterilize your knife before you do the same cut on the variety that you have selected for your scion. The most important part of this stem is to make the cuts clean without burrs and even in angle so that the scion and rootstock will fit together. Once the second cut is made, the next step is securing the scion to the rootstock. 

Making clean cuts with
a sharp and sterile knife

http://www.flickr.com/photos/mmmavocado/4253778663/ 

The scion and rootstock are secured together with budding rubber strips, or plastic grafting tape. Make sure that you have the scion placed in the right direction with the apical side upright, otherwise the graft will not be successful. Because tying or taping the union together is an important step, it requires two people. One person is needed as the grafter, or the person who does the cutting and puts the scion in place and a second person is needed as the tier who will finish the graft by tying the union.

It is essential to make the cuts equal and even and secure the scion and rootstock tightly so that the maximum amount of cambial tissue contact is achieved. Without enough cambial tissues layers matching up between the rootstock and scion, the success rate of the graft decreases drastically. You should work rapidly to ensure the plants do not desiccate and cleanly to ensure smooth cuts that seal together nicely and provide close cambial contact. 

Once the union is tied together, a grafting compound such as Doc Farwell’s Grafting Seal or grafting wax may be used for further structural support and to prevent  desiccation. 

Though the whip graft is most often used for grafting scion to rootstock, it can also be used to graft smaller branches onto larger ones. If this is the case, make sure the scion is placed on one side of the rootstock and not in the middles so that the cambial layers match up. 

As for aftercare, keep a close eye on the graft in the first few days proceeding and keep the rootstock well watered so that plant does not become stressed. Make sure to remove the tape as soon as the graft has taken and the scion begins to grow. Failure to do so may result in girdling, which will restrict the growth of the tree. Once the scion has been growing for a few weeks, the plant can be moved from the greenhouse to an outdoor nursery environment to begin hardening off. By early summer the graft should be well established and the tree will be ready to be transplanted in an orchard. 

http://www.geograph.org.uk/photo/227520

Sources 

Apple Tree. 2012. http://www.2020site.org/trees/apple.html 

Crasweller, R. 2005. Grafting and Propagating Fruit Trees. Penn State College of Agricultural Science Cooperative Extensions. http://pubs.cas.psu.edu/freepubs/pdfs/uj255.pdf

Hartmann, H., Kester, D., Davies, F. and R. Geneve. 1999. Plant Propagation. Pearson Education, Inc. Upper Saddle River, NJ. 

Harry Ricker of Ricker Hill Orchards, Turner Maine.

Methods of Grafting. 2009. University of Minnesota Extension. http://www.extension.umn.edu/distribution/horticulture/components/DG0532c.html

Stoltz, L. and J. Strang. Reproducing Fruit Trees by Graftage: Budding and Grafting. Cooperative Extension Service University of Kentucky.http://www.ca.uky.edu/agc/pubs/ho/ho39/ho39.pdf

Tissue Culture

Propagating Bananas by Tissue Culture 

Banana Plant

http://commons.wikimedia.org/wiki/File:Musa_JPG02.jpg

Bananas are from the genus Musa and the Musaceae family. Edible bananas originated in the Indo-Malaysian area. Banana plants are perennial herbs, though they are commonly mistaken for trees. Today they are grown in humid tropical places and are the 4th largest fruit crop in the world. 

The main method of propagating bananas is vegetatively with daughter suckers or pups. These contain portions of the roots, corm and rhizome from the mother plant. However, propagating bananas by way of tissue culture is preferred for commercial production and has many benefits. Since the explant used for tissue culture is carefully selected from a strong and high yielding mother plant, the plants will be disease free and high yielding. Banana plants grown from tissue culture also yield earlier than conventionally propagated plants. Tissue culture allows a large number of plants to be propagated in a short period of time, which is helpful for bananas since they are a highly demanded crop. 

Working under a laminar flow hood

 http://www.flickr.com/photos/ilri/3974424030/

Preparing the proper work area is essential. Your work area needs to be sterile and dust free to prevent contamination. If you can work under a laminar flow hood, then do so. However, if you do not have access to a hood then working in a box turned on its side will suffice. As long as you have some sort of cover to prevent dust from falling into work working area then you are good. All surfaces and instruments must be sterilized and cleaned prior to beginning the process. 

Select your explant material from shoot tips from young suckers that are roughly 40-100cm in height. From that sucker, cut a piece that is roughly 1-2cm in length and that includes the apical meristem. The material needs to be sterilized first to prevent unwanted pathogens. First dip the explant into 70% ethanol for 10 seconds with tweezers so that the entire plant is emerged. Then place the plant material in a solution of 2% sodium hypochlorite for 20 minutes. Make sure to time this accurately because too little time won’t do the job and too much time with damage the plant material. The final sterilization step is to dip in sterile water 3 times. 

Growing Medium *Note, this is not
a banana plant*

 http://commons.wikimedia.org/wiki/File:Cercis_yunnanensis_-2.JPG

Using a sterilized sharp knife, cut the plant material into pieces between 5 and 10 mm in size. Carefully place the pieces directly onto the medium. Sterilize your knife frequently throughout this process.The medium most widely used, and which I recommend is Murashige and Skoog medium because it contain all the salts and nutrients needed for your plant. You can place as many pieces of explant on the medium as you please, just make sure its not crowded and that there is space for each explant to grow. 

Once you are done, the petri dishes need to be taped closed, preferably using para-film and place in a growth chamber where you can control the temperature, light and humidity. Optimal temperature for banana tissue cultures are 27-30 degrees Celsius and optimal light cycle is 12-16 hours.

You should check for signs of pathogens and diseases daily. You should discard any plant materials that are showing signs of disease or infection immediately to prevent the contamination from spreading. Banana tissue cultures are susceptible to blackening that results from the oxidation of polyphenolic compounds that occur in the wounded tissues. This causes a barrier to form and prevents the plant tissues from taking up the nutrients essential to its survival.  Because of this threat, the healthy explants should be transferred into new petri dishes every 1-2 weeks for the first 4-6 weeks. Ascorbic acid or citric acid in concentrations ranging from 10-150 mg/l can be added to the medium to reduce the chances of blackening. You can also dip the explant in cysteine 50 mg/l before you transfer it into the growing medium. 

Successfully transplanted banana plant

 http://pixabay.com/en/banana-shrub-banana-tree-59650/

For rooting hormones, adding IBA and IAA at 2.25 mg/l and 0.175 mg/l respectively to the growing medium is highly recommended. 

Once roots and shoots are established you need to start considering acclimating your banana plants. Start by taking the top off the petri dish for a period of a few days. A minimum period of 10 days is recommended before transplanting. 

When transplanting, carefully remove the plants from the gel and wash all traces of the gel off. This is important because any gel material left on the plant could be a potential source for pathogens. Transplant the plants into plastic pots at least 6 inches in diameter with a potting mix that consists of 2 parts growing media mix, 1 part perlite and 3 parts vermiculite. This will give the plant roots the proper aeration and drainage that it needs. Make sure the soil is thoroughly and uniformly moistened prior to transplanting. The pots should be kept under a misting bench in a green house. The misting system should be closely monitored in the first few weeks after transplanting because the plants will be vulnerable and you don’t want to over water creating a favorable environment for pathogens or under water causing desiccation. 

Sources 

Banana Tissue Culture. S L V Plant Technologies Tvt. Ltd. http://slvplant.com/pdf/BANANA_TISSUE_CULTURE.pdf

Perez, E. and C. Hooks. Preparing Tissue-Cultured Banana Plantlets for Field Planting. Cooperative Extension Service. University of Hawaii at Manoa. https://scholarspace.manoa.hawaii.edu/bitstream/handle/10125/12175/BIO-8.pdf?sequence=1

Hartmann, H., Kester, D., Davies, F. and R. Geneve. 1999. Plant Propagation. Pearson Education, Inc. Upper Saddle River, NJ. 

Morton, J. Banana. Fruits of Warm Climates. http://www.hort.purdue.edu/newcrop/morton/banana.html#Origin%20and%20Distribution  

Strosse, H. Van Den H. and B. Panis. Cell and Tissue Culture, and Mutation Induction. Labratory of Tropical Crop Improvement. http://www.fao.org/docrep/007/ae216e/ae216e03.htm