Genetic Dissection of Temperature Dependant Sorghum Growth Rates During Juvenile Development

Developing fast growing energy sorghum genotypes for temperate regions is an important breeding goal in order to obtain an alternative crop to maize. Major limitations are low springtime temperatures resulting in prolonged juvenile development. However, the adaptation of sorghum to tropical and subtropical highlands gives hint for certain genetic variation in temperature response and cold tolerance. The goals of the present study are to identify fast growing sorghum genotypes and to detect marker-trait associations describing temperature dependant dry matter growth, leaf growth and chlorophyll fluorescence. A diversity set comprising 194 genotypes was tested in eight controlled environments with temperatures ranging from 9.4 to 20.8 °C. Mean genotype performance, growth rates and base temperatures were used for association studies. Sorghum lines were fingerprinted with 171 DArT and 31 SSR markers. SSR markers were analyzed to obtain the population structure while association studies were performed using DArT markers. Promising marker-trait associations for temperature response of sorghum growth rates during juvenile development were detected on chromosomes 1, 4, 6 and 10. Co-localization of parameters describing leaf growth and chlorophyll content or chlorophyll fluorescence suggests that genotype specific temperature effects on the photosynthesis apparatus are a major reason for the variability of growth rates. Future goals are fine mapping of QTL regions in order to identify candidate genes and develop stable markers enabling marker-assisted selection.