An Efficient System for Agrobacterium-mediated Transformation of Elite Cultivars in Brassica juncea

Efficient genetic transformation approaches play pivotal roles in both gene function research and crop breeding. However, stable transformation in mustard, particularly for different horticultural types, has not been systematically studied and well-established so far. In this study, we optimized the key factors in the genetic transformation of mustard, including the optical density value of Agrobacteria suspension, the age of explants, and the combination of phytohormones at different concentrations. As a result, the optimal conditions for the genetic transformation of leaf and stem mustard included explants derived from 4-day-old seedlings, infection by 0.8 OD 600nm Agrobacteria suspension, and then re-differentiation on the medium containing 2 mg/L trans-Zeatin (TZ) and 0.4 mg/Lauxin (IAA); while those for root mustard were explants derived from 8-day-old seedlings, infection by 0.2 OD 600nm Agrobacteria suspension, and the medium containing 2 mg/L TZ and 0.1 mg/L IAA. Overall, this work provides an effective tool for both theoretical study and genetic improvement of Brassica juncea.