A Dark Incubation Period Is Important for Agrobacterium-Mediated Transformation of Mature Internode Explants of Sweet Orange, Grapefruit, Citron, and a Citrange Rootstock

Abstract

BackgroundCitrus 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 direct production of adult phase transgenic citrus trees.Methodology/Principal FindingsFactors 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 a trifoliate hybrid using the identified factors and factor settings.SignificanceThe 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 a trifoliate hybrid.

Establishment of a Rapid and Stable Transgenic System by Agrobacterium-Mediated Transformation of the Germination Seeds in Diploid Strawberry.

“…2). In addition, Agrobacterium concentrations and infection time are also critical to transformation e ciency [38]. We also con rm that 24-h infection time has maximum transformation e ciency, in consistent with the previous reports in seed transformation [31,32].…”

Kn1 gene overexpression drastically improves genetic transformation efficiencies of citrus cultivars

“…Cervera et al (1998) have shown that greenhouse-grown transgenic plants derived from mature tissues can fruit in 14 months. However, efforts have been made to genetically transform mature citrus tissues but the efficiencies are generally extremely low (Marutani-Hert et al 2012).…”

Organogenesis of Citrus Rootstocks Using Mature Explants

“…In addition, Citrumelo has shown more tolerance to citrus blight (Gmitter et al, 2009). To date, the rate of shoot proliferation from citrus mature tissues remains relatively low compared to juvenile material and little is known about the effects of cultivars, explant type, growth regulators and nutrient substrate on in vitro culture of citrus mature tissues (Marutani-Hert et al, 2012;Tallon et al, 2013).…”

“…Although mature explants have been used for micropropagation in some cases, the high rate of contamination, the low morphogenetic capacity and poor shoot rooting largely impeded their wide application (George, 1993;Curtis & Mirkov, 2012). Lastly, few protocols developed in citrus micropropagation using mature explants but little is known about the effects of genotype, explant type and growth regulators on in vitro culture of citrus mature tissues (Pérez-Molphe-Balch & Ochoa-Alejo, 1997;Bordón et al, 2000;Kobayashi et al, 2003;Pérez-Tornero et al, 2010;Marutani-Hert et al, 2012;Tallon et al;.…”