Novel Technology May Lead To Improved Citrus Varieties

Developing improved, disease-resistant, high-quality crop varieties that benefit growers and consumers may seem like a "difficult" task, but Texas A&M AgriLife Research scientists have found the root of the problem.

AgriLife's research team, led by Dr. Kranti Mandadi, is developing a new biological technology that uses "hairy roots" to grow and propagate disease-resistant citrus plants. Mandadi is an AgriLife research associate professor and faculty member in the Department of Plant Pathology and Microbiology at the Texas A&M AgriLife Research and Extension Center in Weslaco and Better Health at the Agricultural Institute at Bryan College Station.

The focus of their project is to develop new methods to combat troublesome pathogens that infect living plants and inhibit growth in the laboratory for study. One of these microbial pathogens causing citrus greening is a major problem in the citrus industry.

In the year Through 2021, Mandadi is the recipient of USDA's $7 million National Institute of Food and Agriculture, Multi-State Integrated Agriculture Project, as well as a NIFA-designated Citrus Green Center of Excellence.

Director of the Texas A&M AgriLife Center at Weslaco, Ph.D. Strong plant pathogens attack citrus, tomatoes, potatoes, grapes, peppers and other crops grown in Texas, Dirk Hess said. "These pathogens, often carried by insect vectors, cause billions of dollars in agricultural losses each year."

A breakthrough in the treatment of plant diseases

The USDA estimates that regulating citrus orchards could save $3 billion in annual losses.

In recent years, Mandadi and his team at Weslaco have developed a revolutionary method as an alternative method to control the difficult bacteria responsible for citrus greening and other insect-borne diseases such as potato zebrafish disease and potato blight.

"Using pathogen-infected host tissues, we have developed a technology to produce 'hairy roots' that serve as biological vessels for these pathogens to reproduce in the laboratory," he said.

The hairy root screening method has already led to the discovery of new antimicrobial peptides and chemicals with proven efficacy in plant materials, said postdoctoral researcher at AgriLife Research, Ph.D. Sonya Yrigoyen says.

"These antibiotics can be used alone or in combination for short- and long-term treatments to control citrus greening, potato blight and tomato weed," he said.

Now, in their latest research, Mandadi and his team have explored how to use this hair rooting technique to improve plants and improve citrus bioengineering.

Genetic engineering of citrus plants based on hairy roots

Based on their previous success, Mandadi and his team have demonstrated a proof-of-concept for citrus engineering using hairy roots in a recent study titled "Rhizobium rhizogenes-mediated hairy root and plant regeneration for bioengineering citrus plants." In Journal of Plant Biotechnology .

In addition to Mandadi and Yrigoyen, co-authors Ph.D. Manikandan Ramasamy, Michelle Dominguez, B.Sc. and Ph.D. Carmen Padilla is a Scientist at Weslaco AgriLife Research.

"Creating improved plant species, whether through traditional breeding or using the latest bioengineering and CRISPR tools, is labor-intensive and can take years," Mandadi said. "Being able to overcome this hurdle and improve this process, especially for hardy and slow-growing perennials like citrus, could be a game-changer and beneficial for growers and consumers alike.

A better and faster way to grow hardy citrus.

In a recent study, researchers used R. rhizogenes to produce transgenic hairy roots of various citrus species such as grapefruit, sweet orange, bitter lemon, and lime with efficiencies ranging from 28% to 75%. This level of efficiency is at least twice and possibly more than previous citrus processing methods, which makes the process faster and more expensive.

After confirming that the transgenic root had the correct genetics, the team was able to reproduce several identical transgenic plants.

Ramasamy said that although scientists have used many techniques to transform plants in the past, genetically modified tree plants like citrus have been difficult to achieve because of their slow growth and regeneration problems.

"However, we were able to demonstrate a versatile approach for hairy root induction, plant regeneration and clonal propagation using R. rhizogenes, which may be useful for many bioengineering applications and gene modification in citrus and other woody plants," he said.

The proposed process of R. rhizogenes-mediated citrus hairy root induction, regeneration, and propagation will be carried out over a period of six months, preferably 12-18 months, using the previously described transformation method.

"This means we can grow and propagate disease-resistant citrus plants using root tissue and establish them faster than previous approaches," Mandadi said. "Developing citrus and other disease-resistant crops can greatly increase overall productivity."

Mandadi hairy root-mediated transformation can benefit citrus growers in many ways, accelerating the development of new cultivars with higher disease resistance and environmental stress tolerance, improving yield efficiency and food quality.

"The consumer will benefit because they expect to continue to offer their favorite fruits and other products with features they find attractive in their products," he said.

Additional information: Manikandan Ramasamy et al., Rhizobium rhizogenes mediated hairy root induction and plant regeneration for citrus plant bioengineering, Journal of Plant Biotechnology (2023). DOI: 10.1111/pbi.14096

Citation : New technology leads to improved citrus varieties (July 27, 2023), ed. Retrieved August 4, 2023, from https://phys.org/news/2023-07-technology-citrus-varieties.html.

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