Latitude influences growth and phenological development of photo-periodic sorghums in the Semi-arid tropics of Africa

Publikations-Art

Zeitschriftenbeitrag

Autoren

Abdulai, A. L., Kouressy, M., Vaksmann, M., Brueck, H., Asch, F., Giese, M.

Erscheinungsjahr

2012

Veröffentlicht in

Journal of Agronomy and Crop Science

Herausgeber

Wiley

Band/Volume

in press/

Matching phenology with favourable abiotic and biotic conditions is a prerequisite for good varietal adaptation. That is particularly important in the context of climate change because an increase in temperature is most likely to modify the precocity of the varieties. The forecast of the phenology of short-day cereals is complex because flowering depends on both temperature and day length. The effects of photoperiod and temperature can be studied by trials in phytotron, but, high cost prohibits the use of this technique where large numbers of varieties are handled. The day length varies with latitude. Multi-location field trials can be employed for creating a range of environments, but in this type of trials, the great variability of the environments (mainly photoperiod x temperature interaction) often masks the photoperiodic effect. The maturity of the photoperiodic varieties varies according to the sowing date. Trials involving several sowing dates facilitate the study of the effect of small variations of photoperiod on phenology. The objectives of this work are to compare these two last approaches by precisely measuring the effect of the latitude on the development of selected varieties of sorghum sown at staggered planting dates and to verify the precision of our models to predict sorghum maturity. A field experiment in Mali was conducted at the experimental sites of Cinzana (13°15' N), Sotuba (12°39' N) and Farako (11°13' N) in 2009 and 2010. Seven sorghum cultivars representing the diversity of cultivated sorghum in Mali were sown on the 10th of June, July and August each year. The duration of the vegetative phase strongly decreased with the latitude. Although the maximum day-length difference between Cinzana and Farako is less than 8 minutes, for some varieties we observed a reduction in crop duration up to 3 weeks. Some varieties are not photoperiod sensitive in Farako and become photoperiodic in Cinzana. The effect of latitude on the phenology is underestimated by the existing models. To determine the optimal areas for the varieties in West Africa and to forecast the effects of climate change, a correction of the simulation coefficients to take account of latitude is proposed. But, in the end, it will be necessary to develop a new model that will be able to predict the effects of both, sowing date and latitude. More research is needed to understand physiological response mechanisms of the pronounced latitude effects on sorghum phenology.