The fuzzy fantastic kiwifruit, and plant tissue culture
Did you know kiwifruit originated from China?
Don’t let the name fool you. Even though this fruit is synonymous with New Zealand’s culture it actually hails from the opposite hemisphere. The fruit originates from the Yangtze in the valley of Northern China. There are more than 50 species of the fruit, but only two have economic* importance, the green kiwifruit, and the golden kiwifruit.
In 1904, kiwifruit seeds were brought to New Zealand by Mary Isabel Fraser, who had been visiting mission schools in China. In 1906 the seeds found home in the soil of New Zealand, resulting in the first fruits occurring in 1910. The fruit was originally named the Chinese gooseberry due to its taste and origin. Although, it has no relation to the gooseberry family and the name would change due to economic reasons. Fruit exports to the US during the 1950s Cold-War saw berries and melons subjected to high tax tariffs. Therefore, in 1959 Jack Turner suggested renaming the fruit into the popular name it has today: the kiwifruit.
A kiwifruit a day keeps the doctor away
Recent studies found that kiwifruit has a great amount of medical potential. This fruit exhibits high concentrations of antioxidants, antibacterial, and anti-fungicides. The kiwifruit contains more antioxidants than strawberries and double the amount of vitamin C compared to oranges. The fruit is eaten in its natural form or as sweets, ice-creams, juices, pulps and more. Currently, interest lies in the fruit’s peel and seeds. These parts of the kiwifruit contain many bioactive molecules that have human-health benefits.
Economic world of kiwifruit
A recent study suggested that the kiwifruit will likely continue to increase its contribution in the New Zealand’s GDP from $2.6b (USD) in 2016 to $6.1b (USD) in 2030. The same study also suggests that the kiwifruit will remain the top horticultural export of New Zealand till 2030. Therefore, it is important for their economy to maintain kiwi’s agricultural growth.
There are other countries that are also increasing their kiwifruit production. Presently, China is the biggest consumer of the fruit and they have been increasing their own production numbers significantly. Commercial kiwifruit productions also exist in: Italy, India, USA (California), France, Greece, Japan, South Korea, Nepal, and Chile. These countries have ideal climates for the fruit as well as regions which are 1000-1500 m above sea level.
In Indonesia, the fruit is also starting to gain traction as a potential cash crop. However, the main constraint in this region is the availability of high-quality seeds which are identical in their genetics. There are other major constraints in global kiwifruit production. For instance, long juvenile periods and high levels of genetic variation. To create identical individuals many farmers are still using conventional stem cutting techniques. However, these often result in very poor rooting success. This is where plant tissue culture (PTC) comes in. The technique has a multitude of benefits. For a comprehensive outline of the benefits and how this technique can generate profit, read our earlier article: “8 ways plant tissue culture generates profit.”
Exciting discoveries in kiwifruit plant tissue culture
A method for micropropagation using mature seeds of kiwifruit grown in vitro (petri dishes, test tubes, etc.) has shown success. This study by Akbaş and others, found that sucrose with Murashige & Skoog medium yields the best shoot success rates. Furthermore, this study also identified key plant-hormones and chemicals required for successful rooting. Cytokinin being among them. From here more research into optimizing the process have been explored.
As previously mentioned, Indonesia has large potential for kiwifruit production. However, they are limited by their ability to source high quality and genetically identical seeds. Therefore, research into plant tissue culture was started. A study in Indonesia aimed at finding the best gelling agent to grow kiwifruit explants. Different individual gelling agents and combinations were investigated. The results of this study show that the highest explant root, shoot, and leaf growth occur on Swallow Globe 4 g/l + Nutrijel 5 g/l. Applying Phytogel 2.2 g/l also shows positive results in terms of root, shoot, and leaf growth.
In India, a study was done to create an inexpensive micropropagation routine for the kiwi industry. This study had some interesting results. For instance, where and how the tissue was sourced proved important. Also, the nodal cuttings of the kiwifruit tree taken in the winter months had the highest survival rate. This study confirms the use of sucrose as a carbon source for best shoot growth results. Interestingly, using nodal cuttings from explants is a great way to increase production. The survival and success rate of these secondary nodal cuttings are even higher than their primary counterparts.
The process of acclimatization (sometimes referred to as hardening) is essential for plants to move from laboratories to the fields. This is the process of gradually introducing the plants to natural light and environmental conditions. The process can often be expensive if agar is used as the growth medium. However, the study in India found a way around this cost. Using coconut coir in the acclimatizing phase significantly reduces costs and shows the highest success rate. Plants that are hardened in this medium have an 82 % survival rate. Using forest litter exhibits a 70 % survival rate. These alternatives significantly reduce the cost of micropropagation from lab-to-field.
The world is hungry for kiwifruit
The global demand for kiwifruit is climbing. This is due to the demand increases in China and Europe. China and Italy have now become the top producers of the fruit. A title once boasted by New Zealand.
And people are really hungry for the fruit. These green or gold fruits are selling at a rate never seen before. In 2019, the highest levels of kiwi fruit per capita consumption were registered in Greece at 14 kg per person. Thereafter, Italy with 5.66 kg per person and Chile with 4.45 kg per person. Thus, PTC is making it possible to feed the world the fruit it wants by making more kiwifruit trees available the world over.
*Several kiwi varieties are not economically important due to their bitter taste as well as their difficult growth patterns.
By Christos Tripodis | 6-December-2021
About the author
Christos Tripodis was raised in the windy city of Port Elizabeth, South Africa. This southern coastal city is now known as Gqebreha and is the Bottlenose Dolphin Capital of the World. During his time at Nelson Mandela University, Christos focused on physics and biology. Eventually graduating with a BSc Honours in Botany with a focus in ecophysiology and phytoremediation. Currently, Christos is using his communication skills and understanding of botany as an Inside Sales Representative at Lab Associates B.V. When he is not reading or writing you can find him botanizing or in the ocean. His other passions include cooking, martial arts, and languages.
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