Fig.3. Photoperiod trend during growing season Photoperiod Sensitivity of Local Sorghum and Millet Varieties in West Africa Photoperiod Sensitivity of Local Sorghum and Millet Varieties in West Africa Moussa Sanon1,2, Gerrit Hoogenboom2, Seydou B. Traoré3, Benoit Sarr3, Axel Garcia y Garcia2, Léopold Somé1, and Carla Roncoli2 Moussa Sanon1,2, Gerrit Hoogenboom2, Seydou B. Traoré3, Benoit Sarr3, Axel Garcia y Garcia2, Léopold Somé1, and Carla Roncoli2 1 Institut de l’Environnement et de Recherches Agricoles (INERA), 04 P.O. Box 8645; Ouagadougou 04, Burkina Faso 2 Department of Biological and Agricultural Engineering, The University of Georgia, Griffin, Georgia 30223-1797, USA 3 Centre Regional Aghrymet (CRA), BP.O. Box 11011, Niamey, Niger 1 Institut de l’Environnement et de Recherches Agricoles (INERA), 04 P.O. Box 8645; Ouagadougou 04, Burkina Faso 2 Department of Biological and Agricultural Engineering, The University of Georgia, Griffin, Georgia 30223-1797, USA 3 Centre Regional Aghrymet (CRA), BP.O. Box 11011, Niamey, Niger INTRODUCTION RESULTS In West Africa, sorghum and millet are the most common cereals used for feeding millions of people, however, yields are very low. Photoperiod strongly affects the development of local sorghum and millet varieties. Their sensitivity to photoperiod is beneficial to production as the growing season duration is modified to fit the maturity with the end of the rainy season for a large range of planting date (0 to 45 days). Also, it allows reducing the impact of water deficit during the first stages of growth, and avoid kernel exposure to insects and diseases. A better understanding of the photosensitivity of sorghum and millet could contribute to reinforce breeding programs and improve crop management systems. The objective of this study was to determine the photoperiod sensitivity characteristics of the most common varieties of sorghum and millet in Burkina Faso, West Africa. Fig. 2. Determination of critical photoperiod and photoperiod sensitivity slope Climatic parameters from planting dates experiment. Fig.3. Photoperiod trend during growing season Phenology Synchronized flowering of local varieties of millet and sorghum sensitive to photoperiod (fig.4). Larger amount of biomass of local varieties Late maturity of local varieties Panicle initiation date period was larger for improved varieties and short for photoperiod sensitive local varieties Planting and Panicle Initiation (PI) dates for sorghum and millet was large for improved varieties (Sariasso 11) and very short for photoperiod sensitive local varieties (Locale Bobo). Critical photoperiod and photoperiod sensitivity Photoperiod sensitivity slope varied from 700 to 4500 GDD h-1 (fig.5); Improved varieties, varieties from the northern Burkina Faso region, as well as short cycle varieties showed lower photosensitivity than varieties from the southern region; Critical photoperiod that varied from 13.00 h to 13.35 h was higher among varieties from the north. Same relationship found for millet Photoperiod sensitivity decreased with the latitude of the local varieties origin for both sorghum and millet Critical photoperiod increased with latitude both for sorghum and millet (Fig.6). Fig.4. Ranges of planting dates and PI date for millet during the 2003, 2004, and 2006 growing seasons Fig. 5. Relationship between GDD from emergence to PI and photoperiod for sorghum. MATERIALS AND METHODS Planting date experiments were conducted during the 2003, 2004, and 2006 cropping seasons Di Experiment Station (13.2 lat. N and 3.2 lon. W) (Fig.1). To avoid water stress, irrigation was applied when necessary The soil of the experimental area was characterized as Gleyic vertic chromic, Cambisol (FAO, 1988), pH neutral to basic, and, and organic matter of 1.3% The experiment in 2003 consisted of six planting dates that were 10 days apart, starting on 13 June. The experiment in 2004 consisted on six planting dates that were 10 days apart, starting on 14 June. For both experiments, eight sorghum and four millet varieties were used The experiment in 2006 consisted on five planting dates that were 15 days apart starting on 05 June; 3 sorghum and 3 millet varieties were used Phenological observations were recorded when 50% of the population reached flag leaf, anthesis, and physiological maturity. The phenological stages were characterized using the cumulative growing degree days (GDD) from emergence The GDD to panicle initiation (PI) was derived empirically as GDD (PI) = (TTFL-300)/1.199 ((Ritchie, J.T., G. Alagarswamy, 1989), were TTFL corresponds to GDD from emergence to Flagleaf (Fig.2). Fig. 1. Map of Burkina Faso Fig. 6. Relationship between latitude and critical photoperiod or photoperiod coefficient for sorghum and millet CONCLUSIONS In this study, we determined the photoperiod sensitivity for sorghum and millet varieties adapted to local ecological conditions of Burkina Faso Most of local varieties are more sensitive to photoperiod than improved varieties in Burkina Faso. These results could allow for the development of alternative management options based on improved variety selection for a given environment. REFERENCES Ritchie, J.T., Alagarswamy, G., 1989. Simulation of sorghum and pearl millet phenology. In: ICRISAT (Ed.), Modeling the Growth and Development of Sorghum and Pearl Millet. Research Bulletin no. 12, Patancheru, India, pp. 24-26.