Efficiency of Single and Multiple Traits Selection for Yield and Its Components in Varietal Maintenance of Giza 90 Egyptian Cotton Variety

Cotton is an important commercial crop of Egypt. The present study was carried out to study the possibility of selection of elite high yielding plants characterized by the same fiber properties of the superior cultivar Giza 90. To attain this goal two cycles of selection for single trait selection for lint yield/plant and 14 selection indices (desired genetic gain index) were achieved. Average observed genetic gain of the ten selected families after two cycles of selection indicated that LY/P ranged from insignificant (16.57%) for index 2 (LY/P and BW) to 21.63% (P ≤0.01) for index 7 (NB/P and NS/B). Index 2 increased BW by 9.27% (p ≤ 0.05) and UHM length by 2.23% (p ≤ 0.01). Index 7 showed significant genetic gain of 20.26, 21.63, 3.16, 5.44 and 2.785 for SCY/P, LY/P, SI, PI, and UHM length, respectively. Index 3 showed significant genetic gain of 19.71, 21.36, 3.61, 7.82, and 2.65% for SCY/P, LY/P, SI, PI and UHM length, respectively. Index 13 gave significant genetic gain 18.46, 20.55 and 5.76% for SCY/P, LY/P and PI, respectively. Single trait selection for LY/P showed significant genetic gain of 19.75, 20.30 and 14.01% for SCY/P, LY/P and NB/P, respectively. The results indicated that selection index was better than single trait selection in detecting the superior families in LY/P. Generally, it could be concluded that the present program for maintenance and renewing Egyptian cotton varieties is a precise and perfect program to preserve the fiber quality, but, not suitable for improving yielding ability. In consequence, this program should be modified to allow the isolation of superior high yielding off types from the breeding nursery characterized by improvement in one or more fiber quality.