How Novel Biotechnology Could Lead To Improved Citrus Varieties
A new biological technology that develops and multiplies disease-resistant citrus plants using “hairy roots” is under development by a Texas A&M AgriLife Research team led by Associate Professor Kranthi Mandadi at the Texas A&M AgriLife Research and Extension Center at Weslaco.
At the root of their project is developing new ways to fight pathogens, which infect living plants and resist growth in a lab setting for study. One such pathogen causes citrus greening.
In recent years, Mandadi and his team at Weslaco developed a breakthrough method as an alternative means to propagate fastidious bacteria responsible for citrus greening and other insect-vectored diseases such as potato zebra chip and tomato vein greening disease.
“We developed a technology that uses pathogen-infected host tissues to produce so-called ‘hairy roots’ that can serve as biological vessels for the propagation of these pathogens in the laboratory,” Mandadi says.
The hairy root screening technique has already led to the discovery of new antimicrobial peptides and chemicals with proven efficacy in plant materials.
Now, in their most recent study, Mandadi and his team investigated how to use this hairy root technique in plant transformation and bioengineering improved citrus.
Building on previous success, in their latest study called “Rhizobium rhizogenes-mediated hairy root induction and plant regeneration for bioengineering citrus,” recently published in the high-impact Plant Biotechnology Journal, Mandadi and his team showed proof of the concept of engineering citrus using hairy roots.
“Developing new plant varieties with improved genetics using conventional breeding or the latest bioengineering and CRISPR tools can be quite laborious, often taking multiple years,” Mandadi says. “The ability to overcome this bottleneck and improve this process, particularly for hardy, slow-growing, perennial trees like citrus, can be a game changer and a boon to producers and consumers.”
In their most recent study, the researchers used R. rhizogenes to induce transgenic hairy roots from diverse citrus cultivars such as grapefruit, sweet orange, rough lemon, and citron at efficiencies of 28% to 75%. This level of efficiency is at least twice — potentially greater — than those seen with previous methods for citrus transformation, making for a faster and less costly process.
After making sure a transgenic root had the proper genetics, the team was then able to regenerate and clone several identical, transgenic plants from it.
The proposed R. rhizogenes-mediated citrus hairy root induction, shoot regeneration and multiplication process achieved in about six months what typically took approximately 12 to 18 months using the previously described transformation method.
“This means we will be able to develop and multiply disease-resistant citrus plants using root tissue more quickly and get them established much faster than when using the previous approaches,” Mandadi says. “The entire throughput for developing more disease-resistant citrus and other plants will be greatly expedited.”
Mandadi concludes the hairy-root mediated transformation could benefit citrus producers in many ways by speeding the development of new varieties with superior disease resistance, as well as resilience to environmental stresses, increased production efficiency and improved nutritional quality.
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