Benha University; Faculty of AgricultureAnnals of Agricultural Science, Moshtohor1110-041961120230301Quadriallel Analysis of Some Yield Components and Fiber Quality Traits in Egyptian cotton Varieties91828185510.21608/assjm.2023.281855ENALIElhousaryAgronomy Dep. Fac. Agric. Moshtohor, Benha Univ.Journal Article20230124 Six Egyptian cotton varieties and their 45 double crosses were used to evaluating for combining ability and gene action .Results shown that the mean squares of genotypes were highly significant for most studied traits. Further partition of crosses mean squares to its component showed that the mean squares due to 1-line general, 2-line specific effect, 2-line arrangement, 3-line arrangement and 4-line arrangement were either significant or highly significant for most studied traits suggesting the presence of the additive and non-additive variance in the inheritance of these traits. Two-line interaction effect i.e. (S<sup>2</sup><sub>12</sub>),(S<sup>2</sup><sub>25</sub>) and (S<sup>2</sup><sub>34</sub>) showed positive or negative(desirable) the best combination effect for most of yield compounds and fiber quality studied traits. Regarding, the three –line interaction effect, the combinations (S<sup>3</sup><sub>124</sub>), (S<sup>3</sup><sub>125</sub>) and (S<sup>3</sup><sub>134</sub>) were the best combinations for most studied traits. Moreover, the four- line interaction effect point that, best combinations and exhibited desirable effects for most studied traits were (S<sup>4</sup><sub>1346</sub>), (S<sup>4</sup><sub>3456</sub>), (S<sup>4</sup><sub>1235</sub>) and (S<sup>4</sup><sub>1234</sub>). The specific t<sup>2</sup>(<sub>ij</sub>)(<sub>..</sub>) combining ability effects showed that, the better combination t<sup>2</sup>(<sub>14</sub>)(..), for (B/P), (BWg.), (UHM) and (UI), Also, t<sup>2</sup>(<sub>45</sub>)(..) for (SCY/P.g.) and (LY/P.g.) traits. In the same time, the two t<sup>2</sup>(<sub>36</sub>)(..) and t<sup>2</sup>(<sub>26</sub>)(..) were the best for FF trait and the best combination t<sup>2</sup>(<sub>25</sub>)(..) for (FS) trait. Through the specific t<sup>2</sup><strong><sub>(i.)(j.)</sub></strong> combining ability effect noticed that, t<sup>2</sup>(<sub>4.</sub>)(<sub>6.</sub>), t<sup>2</sup>(<sub>1</sub>.)(<sub>5.</sub>), t<sup>2</sup>(<sub>1.</sub>)(<sub>6.</sub>), t<sup>2</sup>(<sub>2.</sub>)(<sub>4.</sub>), t<sup>2</sup>(<sub>1</sub>.)(<sub>3.</sub>), t<sup>2</sup>(<sub>2.</sub>)(<sub>5.</sub>), t<sup>2</sup>(<sub>3</sub>.)(<sub>4.</sub>) as well as t<sup>2</sup>(<sub>3.</sub>)(<sub>5.</sub>), were the best effect combinations for most yield and fiber quality traits. https://assjm.journals.ekb.eg/article_281855_01c74c40acea6975d2f6c6cefb88b2ab.pdf