To improve sorghum grain protein nutritional quality, improved sorghum lines were transformed to
suppress the synthesis of different kafirin sub-classes, or backcrossed into transgenic lines with
improved protein quality. Co-suppression of the alpha-, gamma- and delta-kafirin sub-classes and
removal of the tannin trait resulted in transgenic sorghum lines with high cooked protein digestibility
( 80%), improved Amino Acid Score (0.8) and Protein Digestibility Corrected Amino Acid Score (0.7)
compared to the non-transgenic null controls ( 50%, 0.4 and 0.2, respectively). These high protein
quality lines had a floury endosperm. They also had modified protein body structure, where the protein
bodies were irregular shaped with few to numerous invaginations and were less densely packed, with
a dense protein matrix visible around the protein bodies. When fewer sub-classes were suppressed, i.e.
gamma 1 and delta 2, the endosperm was corneous with normal protein body structure but the
improvement in cooked protein digestibility appeared to be less. Apparently, co-suppression of several
kafirin sub-classes is required to obtain high protein nutritional quality sorghum lines, but this seems to
result in floury-type grain endosperm texture.