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
Many cold-tolerant lines have been isolated. Those lines are evaluated in multi-locations for germination and vigor in the field under early season cold conditions and for combining ability in hybrids. RIL (recombinant inbred line) mapping populations are established or under development to map quantitative trait loci responsible for cold tolerance in sorghum. We also isolated many new staygreen (post-flower drought tolerance) lines, which are confirmed in field experiments and are analyzed for metabolic profile to identify if there is any specific metabolite associated with staygreen traits. The high throughput screening method for drought and cold tolerance was also used to screen the sorghum pedigreed mutant library developed at the Plant Stress and Germplasm Development Lab at Lubbock, TX. Many mutants altered in cold/high temperature and drought tolerance have been isolated. These mutants are under investigation for inheritance and potential application in sorghum improvement. Milestone 4, sub-objective 2B was suspended due to loss of a sorghum breeder; all the milestones are fully or substantially met.
1. Cold-tolerant sorghum lines identified. Early season cold affects germination and seedling establishment and has been considered the most important trait to improve in sorghum breeding. In general, the sorghum hybrids in the US lack cold tolerance. Scientists at the Cropping Systems Research Laboratory in Lubbock, Texas, have isolated many cold tolerance lines from the Chinese sorghum germplasm collection available in the Plant Genetic Resources Conservation Unit, USDA-ARS. In collaboration with sorghum industries, five lines have been demonstrated to confer cold tolerance in sorghum hybrids. These cold-tolerant lines can improve sorghum cold tolerance to catch early season moisture and solar radiation, and boost sorghum yield.
Burow, G.B., Klein, R.R., Klein, P.E., Franks, C.D., Burke, J.J., Xin, Z., Pederson, G.A., Schertz, K.F. 2011. Registration of the IS3620C/BTx623 recombinant inbred mapping population of sorghum (Sorghum bicolor L. [Moench.]). Journal of Plant Registrations. 5(1):141-145.