Genetic programs controlling life history of annual-biennial weeds

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Conyza canadensis is an annual-biennial weed, which exhibits both annual and biennial phenotype. When the seeds of C.canadensis had been exposed to low temperatures during winter, the resultant plants became responsive to flowering stimuli (ungerminated-seed vernalization), showing annual phenotype. Cycloheximide substituted for the ungerminated-seed vernalization. Genetic clones were isolated from the ungerminated seeds incubated in low temperatures using a subtractive differential screening. Nine out of the 19 clones were unknown genes. A strain of C.canadensis originated from Matsumoto district showed obligate annual phenotype. These findings indicate that the ungerminated-seed vernalization is a key ecological factor for establishing the annual phenotype in annual-biennial plants by modifying some genetical and biochemical processes.