Myb transcription factor of cotton and its encoding gene and use

The present invention discloses Myb transcription factor of cotton and its encoding gene and application. The Myb transcription factor, named GhMYB9, is protein with the amino acid residue sequence as Sequence 2 in sequence list, or protein derived from the Sequence 2 with one or several substituent, default or added amino acid residues and possessing the same activity as amino acid residue sequence as that in Sequence 2. The encoding gene GhMYB9 of Myb transcription factor GhMYB9 is one of the following nucleotide sequences: DNA sequence of Sequence 1 in sequence list; and DNA sequence with over 90 % homology with the DNA sequence of Sequence 1 in sequence list and encoding the same functional proteins. The gene of the present invention is significant in breeding new variety of fiber plant, especially of cotton.