1a. Objectives (from AD-416):
1. To develop valuable breeding resources with early season cold tolerance from advanced recombinant inbred populations of sorghum. 2. To continue analysis of male sterile A3 cold-tolerant Chinese lines for studies on maternal/heterotic effects; AIMs mutants in elite background; advancement of populations and conversion of germplasm resources for identification of favorable alleles and full utilization of germplasm. 3. To carry out screening for disease/pest reactions of advanced populations, select lines and analysis of seed quality to integrate resistances to biotic stress with cold tolerance traits. 4. To utilize genomic tools for understanding and deploying cold tolerance in sorghum.
1b. Approach (from AD-416):
This project is a continuation of existing cooperative research on sorghum cold tolerance to start to deliver germplasm products and technologies to the sorghum industry. Primarily, it involves identification of R (restorer) or B (maintainer) fertility reaction of selected RIL lines from BTx623 x PI567946 population developed at USDA-ARS Cropping Systems Laboratory through crosses with A1 or A3 cytoplasmic male sterile lines. Furthermore, development of A1 lines from select B-RIL lines and production of hybrids with elite adapted US and company inbreds will be carried out. Continuation of multi-location testing for early season cold performance will be conducted in Texas, Kansas, Iowa, South Dakota, and Illinois for selected germplasm lines. This research will continue to gather information on heterosis and maternal effects on early season cold-tolerance response from F1 hybrids from crosses of A3 cold-tolerant Chinese lines with elite grain sorghum lines and sweet sorghum. Production of advanced population/germplasm resources for cold tolerance from USDA-ARS at Lubbock, TX, and Stillwater, OK, and partial conversion lines of cold-tolerant Ethiopian germplasm, and development of stable AIMs mutants (B lines) that can serve as novel sources of cold tolerance will be performed. Determination of disease reactions to major seedling pathogen(s) of recombinant inbred lines and select lines and information on seed quality parameters for parents, select RIL lines, and F1 hybrids and analysis of their association with cold tolerance will be gathered. This project will also initiate study of cold-tolerance QTL from available RIL populations using joint genome-wide association analysis and accomplish combined QTL analysis for cold tolerance and disease resistance. Generation of data on single nucleotide polymorphism markers through next generation sequencing will be continued for further understanding of cold tolerance at molecular level.
3. Progress Report:
Moving forwardis a detailed evaluation of previously identified robust cold-tolerant maintainer or B lines (derived from BTx623 x PI567946 population) and 12 pollinators or R lines (derived from RTx430xPI610727 population) based on multi-location trials and genetic studies. Specifically, the new B lines were converted to seed parents (as A lines). These inbred lines were transferred to industry partners and public sorghum researchers for further studies. Genetic studies for combining ability of candidate B lines were evaluated for hybrid performance in crosses with KS female germplasm, and preliminary results showed that among hybrids, consistently higher germination and strong vigor was observed with BTx623/HKZ RIL #228 as B parent. Additionally, RIL BTx623/HKZ RIL #228 is a resistant line to seedling pathogen P. aphanidermatum. Confirmation of top performing cold-tolerant lines from 2011 field screening and 20 additional cold-tolerant lines from large Ethiopian collection were accomplished. Five novel cold-tolerant mutants (in BTx623 background from AIMS population) were successfully backcrossed to wild type parent. The conversion of new cold-tolerant germplasm resources from Ethiopian collection for full utilization of their genetic potential is in progress.