Four successive pure nuclei of Giza 80 cotton cuiuvar (N <')r'\.) (heir
corresponding farmer's seeds (F) were used 10 study the changes thai mIght occur in
yield and quality atter using the seeds in general planting. The field experiments were
carried out in two different locations (Minya and Sohag) through three successive
growing seasons (1997. 1998 and 1999). The experimental design was randomized
complete blocks design wilh four replications.              ,        The results indicate that the source of variability among studied   genotypes and genotypes by locations interactions were, basically, due to the
differences of farmer's seeds (FJ, (N) vs. (F.) and their interactions with
locations. It could be also, concluded that the lint percentage and lint index
characters considered to be good indicators of degeneration as well as the
yarn strength trait; which were affected by the presence of off-type seeds. The
increasing of off-type locks percentage exhibited negative effects on lint
percentage and lint index characters. The results. also. indicated that the
mistakenly handling of the farmer's seeds including off-type seed's in general
tanns might cause deterioration during twO years.