1a. Objectives (from AD-416):
The objective of this project is to develop an improved understanding of the physiological, molecular, and genetic basis of abiotic stress tolerance in sorghum in order to increase the productivity and nutritional quality of sorghum. Over the next 5 years we will focus on the following specific objectives: Objective 1: Develop and utilize new screening tools to identify and create novel sources of drought tolerance in sorghum. Objective 2: Identify quantitative trait loci (QTLs) contributing to abiotic stress tolerance and implement molecular marker-assisted selection for sorghum improvement. Specifically, germplasm collections will be mined for traits that will extend the growing season and enhance yield and biomass production. The genetic bases of cold and heat tolerance will be elucidated initially via genetic mapping of these traits from a new mapping population synthesized specifically for this purpose. Objective 3: Identify physiological traits associated with abiotic stress tolerance in superior germplasm and improved breeding materials. Objective 4: Enhance pre-flowering and post-flowering drought tolerance in sorghum by characterizing physiological drought stress responses throughout plant development, genetic mapping of these traits, identifying photoperiod-sensitive sorghum lines with post-flowering drought tolerance, and combining photo-period sensitivity and post-flowering drought tolerance in one sorghum genotype or line.
1b. Approach (from AD-416):
A comprehensive approach integrating Plant Physiology, Genetic Mapping, and Plant Breeding will be used to study the mechanisms of abiotic stress tolerance in sorghum and to develop superior germplasm with enhanced abiotic stress tolerance.
3. Progress Report:
In FY2012-2013, scientists in Lubbock, Texas, successfully completed the screen of 376 Sudan sorghum germplasm collection for post-flowering drought tolerance, established and characterized three new mapping populations for early season cold tolerance, identified over 20 sorghum multi-seeded mutants that have large potential to improve sorghum yield, and a collaboration with the scientists at the State of Kansas was established to jointly test over 300 breeding lines for drought and cold tolerance under multiple environments. The project was successfully closed and all objectives were completed.
1. New post-flower drought-tolerant sorghum lines identified. Scientists at the Plant Stress and Germplasm Development Unit at Lubbock, Texas, developed a method that can quantitatively determine the degree of post-flower drought tolerance, commonly known as the "stay-green" trait. The method has been published and made available for other researchers. Using this method, they evaluated 376 sorghum lines from the Sudan for the stay-green trait. Three lines have been advanced for further characterization based on our findings. Identification of these lines validates that the stay-green trait is a valuable tool for quickly screening sorghum lines for drought tolerance.
2. Three new mapping populations for cold tolerance established. Cold tolerance in sorghum has been considered as an important trait by the sorghum growers. To improve cold tolerance, scientists at the Plant Stress and Germplasm Development Unit at Lubbock, Texas, developed three large mapping populations with a combined total of 645 inbred lines. One of the populations is formally released and is available for stakeholders and customers through GRIN. Characterizations of various traits that serve as indicator of early season cold tolerance response were performed for all three populations, and top performing recombinant inbred lines were selected and evaluated for fertility reaction. Validation of framework genotyping data was also completed. Additionally, an analysis of variation in soluble sugar metabolites content in germinating seeds for the diverse parents provides evidence of the significance of amylases in variation for cold tolerance. These advances will facilitate enhanced mapping of gene regions involved in early season cold tolerance.
3. Novel multi-seeded sorghum mutants with large potential to improve sorghum grain yield identified. Scientists at the Plant Stress and Germplasm Development Unit at Lubbock, Texas, identified a large class of novel sorghum mutants that have potential to increase sorghum grain yield. Sorghum panicles have two types of florets: the sessile florets that directly attach to a flower branch and the pedicelliate florets that attach to a flower branch through a short petiole. In wild type sorghum, only the sessile florets develop into seeds, while the pedicelliate florets may develop anthers but will eventually abort. The multi-seeded mutants have increased number and size of primary and secondary flower branches and both types of florets can develop into seeds. Compared to the wild type sorghum, the mutants tripled the seed number and doubled the seed weight on individual panicle basis. The mutants are under evaluation for yield increases based on acreage. A patent about the utilization of msd mutants to breed new sorghum hybrids to enhance grain yield has been filed.
Wang, M.L., Xin, Z., Tonnis, B.D., Farrell, G., Pinnow, D.L., Chen, Z., Davis, J., Yu, J., Hung, Y., Pederson, G.A. 2012. Evaluation of sweet sorghum as a feedstock by multiple harvests for sustainable bioenergy production. Journal of Sustainable Bioenergy Systems (JSBS). 2:122-137.