|Awala, S - MINISTRY OF AGRIC NAMIBIA|
Submitted to: International Sorghum and Millets Newsletter
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 1, 2005
Publication Date: December 1, 2005
Citation: Awala, S.K., Wilson, J.P. 2005. Expression and segregation of stay-green in pearl millet. International Sorghum and Millets Newsletter. 46:87-100. Interpretive Summary: These studies identify and develop an assay for the stay-green trait in pearl millet. Stay-green is characterized by the retention of green leaf area at crop maturity under water stress. In other crops, stay-green varieties have greater drought tolerance at crop maturity, greater leaf nitrogen, and contain more basal stem sugars than do senescent genotypes. Stay-green varieties utilize fertilizers more effectively and have improved digestible energy content of forage. The identification of the trait in pearl millet and ability to measure it will be valuable for improving drought tolerance and forage yield and quality of this important forage grass.
Technical Abstract: Delayed senescence, or stay-green, is a mechanism of drought tolerance characterized by the retention of green leaf area at crop maturity under water-stressed environments. Although never documented to occur in pearl millet, the stay-green trait should have multiple benefits in crop improvement. The objectives of two experiments conducted in the field were to 1) quantitatively compare the chlorophyll content of a putative stay-green genotype, 02F266-4, and a normal senescent pearl millet over time, and 2) obtain preliminary information on the inheritance of the stay-green through segregation in an F2 population. Use of the SPAD meter to measure relative chlorophyll content provided a quantitative assessment of the stay-green trait. The data confirmed previous observations that 02F266-4 expressed stay-green characteristics. Any of the upper three leaves evaluated were suitable for measurements, but expression was greatest in leaf 2.Whereas SPAD ratings indicated the magnitude of the relative chlorophyll content at a point in time, a stay-green value could be calculated as a measure of the magnitude and retention of chlorophyll content over time for assessing the distribution of the trait within populations. In both experiments, the retention of chlorophyll was dominant or over-dominant in expression.