Fiber initiation development in Upland cotton (Gossypium hirsutum L.) cultivars varying in lint percentage

The ovules at the stage of fiber initiation from −1 to +1 days post-anthesis (dpa) were studied, using scanning electron microscopy (SEM), in five Upland cotton (Gossypium hirsutum L.) cultivars varying in lint percentage from 28.53% to 43.10%. Our results indicated that on −1 days post-anthesis (−1 dpa), fiber cell protrusions were found in all cultivars, but these protrusions varied among different materials and the differences did not correlate with ultimate lint percentage of each cultivar. At 0 days post-anthesis (dpa), a large amount of fiber cell protrusions appeared on the ovular surface of all samples, and these protrusions had been elongated significantly by +1 dpa. Interestingly, fiber density at +1 dpa of almost all samples was always significantly lower than that at 0 dpa except Simian3, the cultivar with the highest lint percentage 43.10%. This observation suggests that with the expanding of the cotton ovular volume, fiber “diluting” degree on the ovular surfaces might be related to higher or lower lint percentage. Qiannong465, the cultivar with the lowest lint percentage (28.53%), was found to exhibit the fewest fiber protrusions. Rather, many sunken, morphologically abnormal protrusions were observed on the ovular surface at 0 dpa. Correlation analysis suggested that either fiber protrusion density at 0 dpa or fiber elongation density at +1 dpa had a highest positive correlation with lint percentage, secondly with lint index. The grey relational analysis was essentially consistent with these findings. Thus we have identified two important parameters that could provide invaluable predictive information for cotton breeding.