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
A method to screen for the post-flowering drought tolerance (staygreen) trait was tested in the field on known pre- and post-flowering drought-tolerant lines, and the method has been published. New genetic sources of pre- and post-flowering drought tolerance were identified from the Sudan sorghum germplasm collection. These new drought-tolerant lines will be confirmed in the field in the growing season of 2010. Milestone 4, sub-objective 2B was suspended due to loss of a sorghum breeder; all the milestones are fully or substantially met.
1. Selecting drought tolerance from irrigated sorghum. Sorghum grain losses occur annually because of sensitivity to post-flowering drought. Post-flowering drought tolerance is desired; however, it is notoriously difficult to determine because of variable rainfall patterns. Scientists at the Cropping Systems Research Laboratory in Lubbock, Texas, have developed a method that can screen drought tolerance from non-stressed sorghum plants. The method has been successfully tested in the field with known pre- and post-flowering tolerant lines and used to evaluate the core collection of the sorghum germplasm from Sudan. Researchers/breeders now have a tool that can be used to find sorghum lines with improved drought stress tolerance; and new sources of pre- and post-flowering drought tolerance have been identified from the Sudan collection of sorghum germplasm.
2. Sorghum germplasm released. Sorghum populations exhibiting high levels of genetic diversity are needed for geneticists to identify genes responsible for specific traits. Scientists at the Cropping Systems Research Laboratory in Lubbock, Texas, have developed a sorghum recombinant mapping population derived from a cross between IS3620C/BTx623. This population was shown to exhibit a high level of genetic variation and was released for public use. This population serves as an important resource for mapping important agronomic traits in sorghum.
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