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Background Cotton breeding programs mainly focus on improving cotton fibers, but less attention has been paid by breeders to cottonseed oil improvement. Breeding cottonseed for oil content has mainly depended on phenotypic information used to select varieties with high seed oil content. The purpose of this study was to evaluate some cotton genotypes regarding their oil content and other characters related to fiber yield, in order to select genotypes with high oil content and acceptable levels of the other characters. Seventeen different genotypes of cotton were used in this study. A two-year experiment was carried out at Sids Agricultural Research Station, Beni Suef, Egypt, during 2017 and 2018, using a randomized complete block design with six replications. Seed cotton yield, lint cotton yield, boll weight, seed index, embryo index, oil % and embryo oil index characters were recorded. Results The analysis of variance results showed highly significant differences among the genotypes for all the studied traits except boll weight in season 2017. The overall cotton embryo oil % ranged from 33.40 to 40.28 among the genotypes, while the overall cotton embryo oil index ranged from 1.79 to 2.47. Maximum cotton embryo oil % was noted by the genotypes 15 [{(G83 × G80) × G89} × Australian] and 8 [(G 91 × G90) × (G 85 × G 83)], while maximum cotton embryo oil index was noted by the genotype 13 [(G 91 × G 90) × G80]. The results showed positive correlations between seed cotton yield and lint cotton yield, seed index and embryo index, seed index and embryo index oil %, embryo index and embryo index oil %, and oil % and embryo index oil %. Conclusions It could be concluded that using seed or embryo oil percentages as criteria for differentiating genotypes according to their oil content is misleading and the best efficient measure is using the seed or embryo oil indices because they depend on weight basis. Also, Genotypes 13, 15 and 8 were the best genotypes regarding oil % and they could be used in breeding programs for cotton oil improvement.

Background: This study was conducted to investigate the effect of heterogeneity and heterozygosity on lint yield and fiber quality of Egyptian cotton for late planting stress tolerance. Lint yield was recorded in two planting dates among four cotton population types which included homozygous lines grown in pure stands, hybrids grown in pure stands, homozygous lines in blended stands, and hybrids grown in blended stands. Comparisons were made using trait means, blend response, and heterotic response. Stress susceptibility index (SSI) was calculated over planting dates. Results: In normal planting date, the results showed that means of lint yield for homozygous entries (population I and II) were greater than mean yields of heterozygous entries (population III and IV). In late planting date, the results showed that mean of lint yield for some homozygous entries was equal mean yields of heterozygous entries. Regarding the yield, there was no significant difference between inbreds and blend of hybrids. However, the heterozygous populations had a lower (SSI) and more tolerance for late planting than homozygous populations. In late planting date, the two parents G.90 × CB.58 and G.95 had lint yield equal to or greater than means of blends (heterozygous populations). Adding to the two blends of inbreds, [((G.91 × G.90) × G.80)] + [G.90 × CB.58] and [((G.83 × G.80) × G.89) × (G.83 × Deltabine 703)] + [G.90 × CB.58] had the highest lint yield included the best inbred (G. 90 × CB.58) suggesting that blend performance was determined by inbred performance. Conclusions: Cotton blends may not provide buffering against late planting date. Blend response or heterotic response increased with late planting. However, cotton yields can sometimes be increased through the blends. Blends were not better than inbreds, and blend response was not consistent among the blends. Using blends is not recommended to increase yields or tolerance for late planting, and homozygous population's cultivars could result in increased yields relative to blends. Assuming an efficient method for producing homozygous population's cultivars was available, homozygous populations should be a viable option for commercial production to decrease observed losses in late planting date conditions.

Cotton yield is integrated through whole-plant and within-boll yield components. Four Egyptian cotton genotypes (Gossypium barbadense L.) were evaluated for within-boll seed yield (boll weight, bolls per plant, and lint percentage) and yield components (seeds per boll, motes per boll, ovules per boll, seed mass, lint mass, and seed-setting efficiency ). The question arises that how do within-boll yield components differ from old cultivars to recent isolated hybrids? Two commercially available cotton cultivars and two isolated hybrids were evaluated in years 2010, and 2011. Ten plants were hand-harvested by fruiting position. Five bolls from first-and second-position bolls from the middle of the fruiting zone were hand-harvested. One of the two isolated hybrids (G.90 x Australian) produced more bolls per plant with more seeds per boll. This also resulted in a greater number of ovules produced boll and a lower number of motes per boll with this isolated hybrid. The greater seeds per boll of (G.90 x Australian) was concomitant with greater seed-setting efficiency compared with the other two cultivated cultivars.