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This experiment was conducted in order to estimate gene action, combining ability and heterotic effects for yield and quality characters by the line x tester analysis, involving 5 lines and 4 testers with 20 crosses in cotton (Gossypium hirsutum L.). The ratio of general and specific ability variance revealed non-additive gene action effects for seed cotton yield, fiber length, fiber strength and ginning percentage and additive gene action for fiber fineness and reflectance degree. Claudia, Gloria and Bali 308 with high general combining ability were the best combiner parents and could be used for breeding multi-parent combinations. ST-468 x Claudia, Carisma x Carmen, Bali 308 x Gloria and Bali 308 x Claudia were promising combinations for further selection. Heterosis and heterobeltiosis values of most cross combinations for seed cotton yield, fiber strength and ginning percentage were negative direct. It was concluded that due to non-additive gene actions, it is advisable to select individual plants for seed cotton yield, ginning percentage and fiber traits in later generations (F4-F6).

The purposes of this study were to determine the percentage of out-crossing, isolation distance and pollinator insect species for cotton (Gossypium hirsutum L.) seed production in the Aydin region in Turkey. The glandless and red-leaf traits in G. hirsutum were used as genetic markers. Two experiments were conducted over two years that monitored out-crossing in adjacent rows and adjacent plants and established that the percentage of out-crossing varied. The percentage of out-crossing varied between 0% and 13.3% depending on the genetic marker. In the experiment to determine isolation distance, natural crossing percentage was not observed in 2002, while this percentage was 0.8% in the first rows in 2003. In this study, cotton fields were also visited once a week during flowering periods for seven weeks in order to determine the numbers of pollinator insect species, where the only detected species was the honey bee. The numbers of pollinator insects were 2.14% (2002)

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