Résumé
The rate of development of highly photoperiodic and consequently late sorghums adapted to the West-African savannas is reduced during the phases of jointing and panicle development. Slow development, expressed by a long phyllochron or time between the appearances of two successive leaves, is related to the limited size of the panicles of late sorghums. Therefore, variation for phyllochron during plant development could be a way of increasing the potential grain yield of this type of sorghum. Variability for this trait was assessed in the Cirad (Centre de cooperation internationale en recherche agronomique pour le dveloppement) sorghum mini core-collection but none was detected. On the contrary, the rates of development appear to be homogeneous within the species. There was no significant variation observed for the initial phyllochron, following emergence. Although there was large variation in the secondary phyllochron expressed during the jointing period, there were no significant differences among varieties of a similar maturity. Secondary phyllochron was strongly correlated with vegetative phase duration and thus appears to be one of the functions affected by the photoperiod-sensitive response.