الفهرس 
Heterosis and inbreeding depressionOnly 14 pages are availabe for public view
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Abstract
The purpose of this study was to obtain information regarding combining ability of eight cotton varieties (Gossypiu~n barbadense L.) and manifestation of heterosis in their cross combinations. Heterosis is one of the crop breeding tools which offers an opportunity for increasing cotton production and developing a commercial hybrid cotton. The work reported in this study provides some basic information for the cotton breeders regarding selection of parents to be used in future cotton breeding programmes. Five local cotton varieties; G.45, G.83, G.85, G.86 and Dandara and three exotic cotton varieties; Suvin and TNB (from India) and Karshenskey (from Russia) were chosen for this study, and were crossed in all possible combinations (without rec’iprocals) to produce FI hybrids during summer, 1995. paru: Diallel crosses experiments:- In 1996 season, four experiments were conducted to evaluate the eight parents and their 28 Fl’s crosses at Sakha Fanns, Saltha Agricultural Research Station in a rando~nizedc omplete block design with three replications under four different environments as follows:- Env. 1 : Normal plant density with recommended dose of nitrogen fertilizer [50000 plantslfaddan + 60 Kg Nlfaddan (DINI)]. Env.2: Normal plant density with higher dose of nitrogen fertilizer [50000 plants/faddan + 90 Kg Nlfaddan (DIN2)]. Env.3: High plant density with recommended dose of nitrogen fertilizer [75000 plantsifaddan + 60 Kg Nlfaddan (D2N1)]. E11v.4: High plant density with higher dose of nitrogen fertilizer [75000 plants/faddan + 90 Kg Nlfaddan (D2N2)]. The followinp characters were measured; A- Growth habit and earliness ~neasurements:- I- Days to first flower 2- Days to first boll opening 3- Position of first fruiting node 4- Number of fmiting branchedplant 5- Plant height (cm) 6- Earliness index (%) B- Yield and yield component characteristics:- 1- Seed cotton yieldlpl~(tg m) 2- Lint yieldlplot (gm) 3- Boll weight (gm) 4- Lint percentage 5- Lint index (gin) 6- Seed index (gin) C- Fiber properties:- I- Fiber strength 2- Fiber fineness The data iustifv the follow in^ conclusions; W: Effect on varieh and variety crosses performance dGrifing approach:- A- Growth habit and earliness measurements:- 1- Densities (D) mean squares were significant for no. of fruiting brancheslplant, plant height and earliness index. 2- Nitrogen levels (N) mean squares were significant for days to first flower and earliness index. 3- The interactions between densities and nitrogen levels (D x N) were insignificant for all growth habit and earliness measurements. 4- Mean squares and combined mean squares of genotypes, parents and crosses were significant for growth habit and earliness neasurementsa t and over the four different environments. 5- Parent Vs. crosses mean squares were significant for all growth habit and earliness ineasureinents at some different environments, whereas parent Vs. crosses combined mean squares for the growth habit and earliness nieasureinents were significant except plant height.