WhatsappPragmatic production of the purposeful papaya
Papaya; a functional fruit
This tasty and aromatic fruit is grown in tropical and subtropical environments and is known for its soft and sweet flesh. However, the papaya is more than a tasty snack. Unripe papaya fruits contain high amounts of latex, which is the primary source of a cysteine protease enzyme, called papain. The main function of this enzyme is to break down proteins, which makes it useful in various industries.
There are also a whole host of health benefits associated with the consumption of papaya and papaya derived products. Being a good source of the antioxidant beta-carotene, the papaya can aid in asthma and prostate cancer prevention. The papain, fiber, and water in this fruit aids in digestion. Choline is another principal nutrient found in papayas that helps our bodies. It aids in sleep, muscle movement, learning, and memory. Choline does so by maintaining the structure of cellular membranes, aiding in the transmission of nerve impulses, assisting in the absorption of fat, and reducing chronic inflammation. So, there are plenty of reasons why a papaya a day will keep the doctor away!
Conventional papaya propagation
We have already learned that the papaya is very versatile fruit when it comes to it's consumption, it's production is no different. Papaya varieties can be dioecious (i.e., male or female), but they can also exist as hermaphrodites (both male and female flowers on the same plant). The dioecious Australian and African varieties of Honey Gold and Richter Gold are popular due to their high output and flavor. Whereas the hermaphrodite varieties grown in Malaysia and the Philippines are favored in these countries due to their high output and crop consistency throughout generations.
The dioecious papaya varieties require a male tree to fertilize a female tree. This often results in fruit characteristics changing over generations. Another challenge when farming the dioecious varieties is the ability to identify the sex. Sex determination can only occur in the flowering phase or via genetic analysis. Using the genetic approach is costly as every plant would have to undergo analysis, making it an expensive endeavor.
The majority of papaya propagation is done via seed propagation. In some countries, such as South Africa, vegetative propagation is being utilized, which requires plant cuttings. The problem with this method is that not all papaya varieties have the same tendency to produce multi-branches. Therefore, hindering the ability of vegetative propagation. The papaya is a perennial that can produce fruit year-round under ideal conditions. Although, the production is often limited by diseases and parasites. There is good news though. Biotechnology can revamp the papaya industry and make it highly productive.
Papaya plant tissue culture, the pragmatic propagation
Using plant tissue culture (PTC) has shown positive results in the papaya industry. A papaya variety known as Maradol has performed well using PTC. The elongated fruit produced by hermaphrodites is preferred over the rounded fruit produced by females, with respect to the export of this variety. Therefore, commercial Maradol farms require 100% hermaphrodites in their farms. Commercial farmers using seeds yielded 75% hermaphroditism or lower. This requires the farmers to plant more seedlings, water and fertilize them for two months and then eliminate 25% of those plants. This is a costly procedure.
A four-year commercial-scale field-trial of PTC micropropagated Maradol showed plants conserved hermaphroditism entirely (100%) in their flowers and consistently (100%) produced fruits that were elongated in shape. While the control plants (non-PTC) derived from seeds showed only 75% hermaphrodite flowers. This meant 25% of the farm's yield was the non-export grade rounded fruits. The fruit size and yields between the PTC and seed derived hermaphrodite plants were also compared. With regards to fruit appearance and quality, fruits from both types of production were equivalent.
Plant tissue culture techniques used in the papaya industry
Organogenesis
This method has not been studied extensively in the papaya industry. Although, there have been some positive results. A protocol for micropropagation of the Indian papaya variety Co7 was developed using epicotyl segments by direct organogenesis from in vitro papaya seedling plants. Another high efficacy micropropagation protocol for the papaya variety, Rajshahi-red, developed by using petiole segments and indirect organogenesis.
Somatic embryogenesis
This method of PTC has been the most widely studied in papaya. Currently several protocols exist for the in vitro micropropagation of papaya using somatic embryogenesis (SE). This technique addresses the difficulties that occur during conventional seed proliferation as well as the absence of an actual method for early sex determination. SE has also been used to aid in cross breeding papaya species and the proliferation of pest tolerant papaya. Somatic embryos can also be encapsulated in an alginate capsule to be preserved via cryopreservation. This helps preserve valuable genetic material in case of natural disasters or occurrence of a devastating disease.
To delve deeper into the topic of somatic embryogenesis and the factors influencing SE read our corresponding articles.
Cell suspension culture
Cell suspension culture has been shown to work for mountain papaya. This method has improved asexual propagation rates in the mountain papaya. Researchers have also found that a liquid medium is better than a solid medium for the conversion of a higher number of somatic embryos during early stages. You can learn more about cell suspension culture in our overview article.
The papaya is a versatile plant that has yet to reach its full potential. Its ability to exist within so many different industries gives it a high profitability potential. Plant tissue culture can surely help the papaya industry expand beyond its current limitations.
For more informational articles on growing different crops using PTC, keep checking this space!
By Christos Tripodis | 12-April-2022
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.
References
- Al-Shara, B., Taha, R.M., Rashid, K. (2018). Biotechnological methods and limitations of micropropagation in papaya (Carica papaya L.) production: a review. The Journal of Animal & Plant Sciences 28(5), 1208–1226. ISSN: 1018-7081
- Islam, M.N., Molinar-Toribio, E.M. (2013). Development of a meat tenderizer based on papaya peel. Peer Observation Based on Conceptual Maps: A Strategy to Promote the "Scholarship of Teaching and Learning" at the Technological University of Panama. RIDTEC, 9 (2).
- Talavera, C., Espadas, F., Contreras, F. and Santamaría, J.M. (2007). Field performance of 100% hermaphrodite micropropagated papaya plants. 2nd International Symposium on Acclimatization and Establishment of Micropropagated Plants. Riviera Maya, Mexico 748, 219-222. DOI:10.17660/ActaHortic.2007.748.29
- Talavera, C., Espadas, F., Contreras, F., Fuentes, G., Santamaría, J.M. (2009). Acclimatization, rooting and field establishment of micropropagated papaya plants. Acta Horticulturae 812, 373–378. ISSN: 0567-7572
- Ware, M. and Butler, N. (2017). Papaya fruit: Health benefits, uses, and risks. [online] Medicalnewstoday.com. Available at:<https://www.medicalnewstoday.com/articles/275517?c=923219902471> [Accessed 17 February 2022].