|Mirkov, T. Eric - Texas A&M University|
Submitted to: PLoS One
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/12/2012
Publication Date: 10/17/2012
Citation: Hert, M.M., Bowman, K.D., Mirkov, T., Evens, T.J., Niedz, R.P., Mccollum, T.G. 2012. A dark incubation period is important for Agrobacterium-mediated transformation of mature internode explants of sweet orange, grapefruit, citron, and a citrange rootstock. PLoS One. 7(10):1-11.
Interpretive Summary: A citrus tree produced from a seed takes 2-20 years to produce fruit. To develop a new citrus variety takes about 30 years, with much of the time waiting for trees to produce fruit. This long time to produce fruit increases the time it takes to develop new citrus varieties where fruit yield and quality are important factors when deciding if a selection should be released as a variety. Citrus trees produced by plant tissue culture act like seed in that they also take a very long time to flower and produce fruit. Because genetic engineering is becoming an increasingly important tool for producing new citrus varieties, particularly varieties that are resistant to pests and diseases for which there is no natural resistance, reducing the time to produce fruit would speed up the development of genetically engineered citrus. This study reports a method to produce genetically modified trees of four citrus types including sweet orange, grapefruit, citron, and citrange.
Technical Abstract: Background: Citrus has an extended juvenile phase and trees can take 2-20 years to transition to the adult reproductive phase and produce fruit. For citrus variety development this substantially prolongs the time before adult traits, such as fruit yield and quality, can be evaluated. Methods to transform tissue from mature citrus trees would shorten the evaluation period via the production of adult phase transgenic citrus trees directly. Methodology/Principal Findings: Factors important for promoting shoot regeneration from internode explants from adult phase citrus trees were identified and included a dark incubation period and the use of the cytokinin zeatin riboside. Transgenic trees were produced from four citrus types including sweet orange, citron, grapefruit, and citrange using the identified factors. Significance: The critical importance of a dark incubation period for shoot regeneration was established. These results confirm previous reports on the feasibility of transforming mature tissue from sweet orange and are the first to document the transformation of mature tissue from grapefruit, citron, and citrange.