Grafting Imparts Glyphosate Resistance in Soybean

Grafting is a widely-adopted cultural method to incorporate desired traits of rootstock with those of the scion and has been used successfully to address many biotic and abiotic stresses, including drought/waterlogging, insects, and diseases. However, it is not known if a herbicide resistance trait can be transferred across a graft union. Using Roundup Ready® (RR; glyphosate-resistant) soybean grafted with conventional (CN; nontransgenic and glyphosate-sensitive) soybean, we show that grafting is capable of transferring glyphosate resistance from RR rootstocks to CN scions. Grafts of CN/CN (scion/rootstock), CN/RR, RR/CN, and RR/RR were treated with potassium salt of glyphosate at 0.28, 0.84 and 1.68 kg ae ha−1. The CN/RR plants survived glyphosate treatment at 0.84 and 1.68 kg ha−1 while CN/CN plants were killed, indicating that glyphosate resistance is systemically mobile across the graft union. Intraspecies transfer of glyphosate resistance was unidirectional from root to shoot, since RR/CN plants were killed by glyphosate. The glyphosate resistance trait is conferred by CP4 5-enolpyruvylshikimate-3-phosphate synthase (CP4-EPSPS); therefore, we further examined whether CP4-EPSPS played a role in the phenomenon. CP4-EPSPS was detected in the CN scion of CN/RR plants by enzyme-linked immunosorbent assay (ELISA) but only 0.001% of that detected in RR leaf. This concentration is unlikely to have contributed significantly to the glyphosate resistance observed in CN/RR plants. Amino acid systemic trafficking and/or tissue specific glyphosate resistance are more likely the reasons for this phenomenon. These results show that grafting a transgenic herbicide-resistant rootstock to a nonresistant scion can confer resistance to the entire plant. Nomenclature: Glyphosate; soybean, Glycine max (L.) Merr. El injertar es una práctica cultural ampliamente adoptada para combinar caracteres deseados de un patrón con aquellos del injerto y ha sido utilizada exitosamente para lidiar con muchos estreses bióticos y abióticos, incluyendo sequía/inundación, insectos y enfermedades. Sin embargo, no se sabe si el carácter de resistencia a herbicidas puede ser transferido a través de la unión del injerto. Usando soya resistente a glyphosate (RR) injertada con soya no resistente a glyphosate (CN), nosotros demostramos que los injertos son capaces de transferir la resistencia a glyphosate de un patrón resistente a tejido convencional injertado. Injertos de CN/CN (injerto/patrón), C