Fig. 3

Efficient and convenient screening in the primary stage of tissue culture. a, b Examples of positive tissue with red fluorescence by visual screening. Strong red fluorescence could be observed in calli and shoots. c, d Examples of negative tissue with red fluorescence by visual screening. Nearly no or weak red fluorescence in calli and shoots could be observed. e–l Diagram of the convenient screening for calli and shoots at the primary culturing stage. Red fluorescence could be clearly observed in calli and shoots by visual screening with a hand-held green fluorescent flashlight. The yellow arrows indicate red fluorescence. a, c, e–h are in the white field, while b, d, i, g, k and l are in the excitatory light field