2019-11-01T00:00:00The present study contained 16 testing genotypes and was laid out in a Randomized Complete Block Design (RCBD) with four replications at Werer Agricultural Research Center (WARC). This experiment was conducted with the objective of evaluating the performance of segregating inbred lines. The analysis of variance revealed that the tested genotypes differed significantly (p<0.05) in number of sympodial branches plant-1(SYM), Plant height (PLH), boll number plant-1 (BOP), Boll weight (BOW), Seed cotton yield ha-1 (SHA),Ginning percentage (GP),and lint yield ha-1(LHA), hundred seed weight (HSW), micronaire (Mic), upper half mean length (Uhml), Fiber Strength(Str) and Short fiber content (Sf). A one degree of contrast between the mean of the 14 F5 inbred lines and the mean of the two parents was significant for all traits except some traits. All 14 inbred lines included in this study were better than both parents in SYM, BOP, SHA, GP, and LHA, but were inferior to both parents in BOW, indicating that there was transgressive expression of the majority of traits. Additive genes were dispersed in the two parents for these traits. The mean separation analysis of seed cotton yield revealed superior inbred lines that excelled their parents viz., K (5170.3kg/ha), G (5072 kg/ha) and I (4987 kg/ha). The yield advantage obtained from most of the inbred lines was more than 10% in both seed cotton yield and lint yield compared with the parents. The inbred line with the highest value was superior to the parent with the highest value by 34% in SYM (inbred line I (15.25 vs 11.38), by 39.94% in BOP (inbred line I; 17.59 vs 12.57), by 26.7% in SHA (inbred line K; 51.7 vs 40.8), by 33.1% in LHA (inbred line K; 20.92 vs 15.72). Deltapine-90 was inferior to Delecero in Upper half mean length (Uhml) (27.90 vs 32.92), Uniformity percentage (80.4 vs 83.88), and in Strength (25.78 vs 36.33). The higher fiber quality of Delecero was expressed in its higher Uhml, strength, and its lower percentage of short fiber content (Sf, 8.0%).Deltapine-90 could not contribute any additive genes for the improvement of fiber quality traits like Uhml, strength and uniformity. It had one of the lowest means for the three traits. Breeders should look for appropriate germplasm that can contribute to the improvement of these fiber quality traits. Delcero should be backcrossed, with high yielder inbred lines to transfer its main fiber quality trait like fiber strength and length. Thus, these inbred lines could be potential varieties for future use by combining important quality traits through back crossing.