MORPHOLOGICAL AND MOLECULAR MARKER STUDIES ON SOME COTTON OFF-TYPES AND THEIR DETERIORATION EFFECTS ON CULTIVARS.

Maintenance is considered essential in breeding program to maintain high quality properties and prevent any deterioration for these traits. Thus, study of off-type plants under commercial scale is a must to isolate these plants. Two varieties (Giza 86 and Giza 88) and their off-types were collected from commercial cotton area. The original maintained varieties and their off-types were grown during 2015, 2016 and 2017 growing seasons. Significant differences were observed between (Giza 86 and Giza 88) and their off-types for all traits except for (F.S) in Giza 86. Genetical comparison was done by using a random amplified polymorphic DNA (RAPD) analysis and genetic relationships between genotypes were estimated using the cluster analysis. Analysis of variance revealed highly significant differences among all genotypes under study for growth, earliness, yield and its components as well as fiber properties. The off-types showed more vigorous growth while Giza 86 and Giza 88 (pure) gave the highest values of earliness, yield and fiber traits. The cluster analysis based on all studied traits showed two main groups, Giza 86 (pure) represented the first group. Meanwhile, the off-types represented the rest groups. Giza 88 (pure) revealed the same results. Dissimilarity between the (Giza 86, Giza 88) and their off-types were the highest. The results cleared that the mean performance of the standard varieties Giza 86 and Giza 88 exhibited the best values for most traits, while the off-types had the worst values of both yield and fiber traits, especially Fiber length (F.L.), Fiber fineness (F.F.), Yellowness (+b) and Brightness (RD%). This obligates the cotton breeders to exclude the off-type plants from the fields of original cotton varieties, during the purification of seed certification fields of cotton varieties. [ABSTRACT FROM AUTHOR]