2012 Annual Report
The Drought Tolerance project seeks to unlock the rich store of drought tolerance genes that exist in the USDA’s preserve of soybean germplasm. This preserve was formed by scientists through decades of work, combing the globe to find exotic soybean. This reservoir of exotic diversity, although collected by scientists, was produced originally by over 3000 years of ‘on-farm breeding’ in Asia, in which farmers selected and adapted the soybean for human use under a range of climate conditions. Special genes for drought tolerance, bred into soybean so long ago by these ancient farmers, are key to coping with the problem of drought in the USA today. The drought problem is so severe for our farmers in the USA because U.S. varieties do not presently contain these special drought genes from Asia. The central theme of our drought tolerance work is that we can ‘turn the tables’ on drought in the USA by putting the world’s genetic resources in soybean to work on U.S. farms. To that end, the United Soybean Board drought tolerance project coordinates the research activities of 8 scientists and 7 research institutions in the Midwest and South. All of this effort is aimed at transferring drought genes from exotic Asian material into adapted genetic materials which will protect agriculture from damaging droughts.
The drought team employed DNA markers to tag genes (quantitative trait loci; QTL) for increased yield under drought stress. A major portion of the research in Georgia has been devoted to this effort. Two approaches were taken to confirm the genomic location of stress-yield QTL identified in soybean PI 471938, and to determine the impact of the QTL on seed yield in stress environments. First, the three major stress-yield QTL were validated using marker-selected F6-derived lines from Hutcheson x PI471938. Eight groups of lines representing all possible allelic combinations of the three QTL were evaluated at multiple locations. The second approach was to develop and test near-isogenic lines (NILs) for all combinations of stress-yield QTL. These lines were developed by reselection within individual F4:8 lines descended from F4 plants that had residual heterozygosity in the regions of each of the four QTL. The F8-derived NILs are homozygous for either the PI 471938 or Hutcheson allele at one of the QTL, and are approximately 99% genetically identical otherwise. The near isogenic lines (NILs) are being compared for drought response and agronomic performance in a wide range of environments. Multiyear data confirm the positive impact of the ‘slow wilt QTL’ on yield. Four slow-wilting QTL were identified which are derived from slow-wilting drought-tolerant exotic soybean PI 416937 x cultivar Benning. Follow-up validation testing of phenotypic extreme is underway at multiple locations in 2012.