Abstract

Yield and yield stability of sorghum [Sorghum bicolor (L.) Moench] and pearl millet [Pennisetum glaucum (L.) R.Br.] are highly influenced by flowering time andphotoperiodic sensitivity in the arid to semi-arid regions of West and Central Africa.Photoperiodic sensitivity is the key adaptation trait of local landraces because it assures flowering at the end of the rainy season, independent of variable dates of planting. Flowering time genes are mainly integrated into four pathways with close interaction among each other: Vernalization, autonomous, GA (gibberellic acid) and photoperiod. In the GA pathway, maize D8, wheat RHT1 and rice SLR have been identified as homologous genes to the Arabidopsis GAI, which is a negative regulator of GA response. We have identified two homologous genes to D8: Sorghum SbD8 and pearl millet PgD8. These genes were expressed in the root and leaves of sorghum and pearl millet as revealed by EST database search and reverse transcription PCR, respectively. The genetic diversity of SbD8 was considerably lower than that of PgD8. The extent of linkage disequilibrium in PgD8is lower than that of maize D8. SbD8 and PgD8 polymorphisms might be appropriate for dissection of photoperiod sensitivity using association mapping approaches.

Key words: DELLA proteins, GA pathway, flowering time, photoperiod sensitivity, sorghum, pearl millet.