Objective 1:
? A population of 207 recombinant inbred lines (RIL) in the F11 generation was developed from the cross between a wild and a cultivated soybean line.
o This RIL population was evaluated for the resistance to iron deficiency chlorosis (IDC) under field conditions for three years. A total of 6 QTLs associated with the resistance to IDC were identified. The QTL alleles that enhance the IDC resistance were derived from both cultivated and wild soybean lines.
? Eleven RILs were selected to cross with a local cultivar to pyramid the IDC-resistance alleles using recurrent backcrossing and marker-assisted selection strategies.
o This RIL population was also evaluated for the resistance to soybean aphids for two years.
? Heritability estimates for the trait is 0.54
? 49 new SSR markers screened and 28 identified to be polymorphic and can be used in marker assisted breeding
Objective 2:
? Specific pathways and ~2000 target genes identified for genetic targeting and identification of novel mechanisms of drought tolerance
? Accumulation of the phytoalexin coumestrol under water stress has been identified as one of the most dramatic changes in metabolites.
? Specific functional markers identified to be used in diagnostic tool development
? Proteomics techniques established to study soybean leaf and seed proteins including the identification of specific proteins associated with drought stress in the leaves
? Ascorbate-glutathione pathways identified as biomarker for drought tolerance in soybean
? Novel mechanism associated with photosynthesis identified in slow-wilting lines
? Genes associated with nodule development, nitrogen fixation and transport with potential for manipulation to enhance N availability during drought stress and/or herbicide injury
? A catalogue of microbes colonizing soybean roots with isolates potentially providing beneficial interactions
? Identification and characterization of soybean signaling proteins (GmMAPKs) that mediate responses to drought stress and nitrogen fixation.
Objective 3:
? Genes and genetic material with altered leaf architecture and stem hair development towards enhanced yields and insect/stress resistance.
? Promoter analyses have identified both known and novel switches that turn on drought-responsive genes.
? Metabolomics, proteomics and transcriptomics reveals that new synthesis of amino acids occurs. These act to protect the plant from dehydration.