Four near-isogenic lines of cotton with different genes for bacterial blight resistance.

The development and genetic characterization of four near-isogenic lines (NILs) of cotton (Gossypium hirsutum) is described herein. Each line contains a single, but different, gene for resistance to bacterial blight caused by Xanthomonas campestris pv. malvacearum. The lines were derived using at least six backcrosses to the susceptible recurrent parent 'Acala 44', followed by single plant-progeny row selection for uniformity. The NILs are homozygous for the B-2, B-4, B-ln, or b(7) genes and are designated as AcB2, AcB4, AcBln,, and Acb(7), respectively. In the 'Acala 44' background, B-2, B-4, and B-1, are partially dominant genes; b7 is partially recessive. Relative strengths of resistance conferred by those genes toward race 1 of the pathogen were B-4-b(7)>B-ln-B-2. B-4, B-ln and b(7) each conferred resistance toward X. campestris pv. malvacearum carrying a single avirulence gene, whereas B-2 was less specific.