Submitted to: International Sorghum and Millets Newsletter
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/9/2006
Publication Date: 12/1/2006
Citation: Burow, G.B., Franks, C.D., Burke, J.J. 2006. Evaluation of anthocyanin pigmentation as an indicator of chilling sensitivity of sorghum seedlings. International Sorghum and Millets Newsletter. 47:39-42.
Interpretive Summary: Sorghum (Sorghum bicolor) is one of the five most important grain species in the world. It is highly adapted to warm and dry conditions making it a useful crop in areas where irrigation is limited or unavailable. In the Southern Plains of the United States, where water availability for agriculture is becoming scarce, cultivation of sorghum is an ecological and water friendly production system that is amenable to highly mechanized large-scale agricultural systems. However, sorghum is sensitive to chilling stress, which is the prevalent abiotic stress condition that occurs in temperate regions during the early spring cropping season. It is widely recognized that sorghum cultivation in the temperate regions can be greatly aided with chilling tolerant sorghum varieties. To facilitate screening for seedling tolerance to chilling stress, alternative screening procedures that permit higher throughput and evaluation of easier to score phenotypes are desired. In this study we characterized the response of fourteen diverse sorghum lines that showed varying levels of anthocyanin pigmentation during chilling stress and determined the relationships of pigmentation to seedling growth and vigor parameters. The results indicate that low temperature-induced anthocyanin accumulation in sorghum can be a stress-induced indicator of chilling sensitivity, and that levels of anthocyanin accumulation are related to the degree of chilling sensitivity.
Technical Abstract: Sorghum is a tropical crop that has been successfully bred to flower under temperate day lengths, but its establishment is limited by early to late season chilling stress. Sorghum lines with enhanced chilling tolerance are valuable; however, germplasm selection in the field is beset by annual variability in early season temperatures. Here, we report the development of a laboratory screening technique that uses the chilling-induced synthesis and accumulation of anthocyanin as an possible indicator of a sorghum lines’ sensitivity to low temperatures. Analysis of fourteen diverse sorghum lines showed genetic variability in anthocyanin accumulation following an 8-day treatment at 17C day/ 12C night temperature regime. Growth of seedlings based on fresh and dry weights of shoots and roots indicated that sorghum lines with low anthocyanin exhibited higher biomass (per seedling) than those lines that accumulated anthocyanin. Further, sorghum lines with low anthocyanin recovered faster based on higher biomass accumulation when the cold-treated seedlings were transferred to 24C day/20C night treatment for 3 days. Early season field trials of the lines evaluated in the laboratory showed that the lines that did not accumulate anthocyanin in the laboratory assay accumulated greater seedling biomass in the field, thereby reaffirming the usefulness of the laboratory screening technique for selection of cold-tolerant sorghum.