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The extent of natural crossing in cotton (Gossypium hirsutum L.) was studied in 2 experiments conducted in Greece during 1998 and 1999, using glandless and red-leaf traits as genetic markers. The glandless line was planted in the middle, and the red-leaf both in the middle and the corners, of a commercial cotton field. In the first experiment where estimation of natural crossing was based upon gland status, the percentage ranged from 1.67% to 2.67% in adjacent rows, dropped to 1.42% in plants 2 m apart, and declined to almost zero after 10 m. In the second experiment, where the red-leaf marker gene was used, the mean of natural crossing was 3.85% in adjacent rows, fell to 2.79% in plants 2 m apart, and progressively diminished to 0.31% after 10 m. The mean natural outcrossing in different rows was almost the same in both experiments at the middle of the field and was actually double at the corners. Differences in the extent of natural crossing between the middle and the corners of the field continued to be significant up to 4 m distance. In all cases, distances greater than 10 m among cottons were sufficient to minimise out-crossing ranges.

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The present study aimed to evaluate the resistance in water stress conditions of the cultivated varieties in Greece, taking into consideration not only the economic importance of cotton worldwide and especially in Greece, where almost 10% of the agriculture land was cotton cultivated, but also the importance of the factors which interfere in its seed germination. Eleven cotton cultivars were evaluated for germination efficiency concerning both, the relevant percentage and the germination rates. Seeds from selected varieties cultivated in Greece, were placed for seven days, in conditions of increased osmotic pressure achieved by gradually increasing concentrations of polyethylene-glycol solutions. A differentiation in cultivars behavior concerning the percentage and the germination rate was observed. Among the eleven cultivars tested "Hermes" was the least and "Sandra" was the most affected concerning the two measured parameters. The remaining cultivars are graded in intermediate order. In all cases the cultivar × polyethylene-glycol interaction was significant.

Seeds from two locally adapted cotton cultivars, Eva and Zeta-2, were irradiated by 300 Gy γ-irradiation in order to create useful variability for earliness within each cultivar, and then to select for desirable recombinations. Selection for earliness was applied in the M2 generation and the earliest 2% of the mutants were selfed for further evaluation. After eliminating the undesirable phenotypes, the remaining material was sown in progeny rows as the M3 generation. Selection for earliness based upon morphological and physiological characteristics resulted in 5 early mutants from cv. Eva and 3 early mutants from cv. Zeta-2. These lines were further evaluated the following year for earliness, yield, fibre, and seed quality in 3 locations across the Greek cotton belt, using a randomised complete block experimental design with 4 replications. Among the 5 early mutants of cv. Eva, only one was consistently early at all 3 locations, whereas the other 4 mutants showed significant differences in the first growth stages. From the 3 early mutants of cv. Zeta-2, one was consistently early at all 3 locations. Plant height, lint yield, length, micronaire, strength, etc., as well as oil %, protein %, and gossypol %, were not significantly different from the untreated checks.