2012 Annual Report
1a.Objectives (from AD-416):
Phenotype a soybean mapping population for environmental stress factors.
1b.Approach (from AD-416):
Random inbred lines (RILs) are nearing final stages of development and 192 RILs will be selected for marker assisted mapping of resistance genes. The RILs will be assayed for single nucleotide polymorphisms to identify markers for mapping. The RILs will be assessed for response to drought, iron deficiency chlorosis, salt stress, aluminum stress, and ozone stress. Injury scores and DNA marker results will be related through QTL analysis.
This research is related to Objective 3 of the parent project to identify soybean germplasm that will contribute to development of stress tolerant cultivars.
A mapping population of random inbred lines has been developed from a cross between tolerant (Fiskeby III) and sensitive (Mandarin Ottawa) genotypes. Each random inbred line will be assessed for response to each abiotic stress factor and these phenotypic data combined with DNA marker data to construct linkage maps for each factor.
DNA was extracted from root tips of 240 random inbred lines and the Fiskeby III and Mandarin Ottawa parents. Assay of single nucleotide polymorphism (SNP) DNA markers was been completed for each random inbred line to provide data for the linkage map to be used for DNA mapping as complete sets of phenotype data become available.
The screening of the mapping population for ozone response was completed using greenhouse exposure chambers located in North Carolina with the Fiskeby III (ozone-tolerant) and Mandarin Ottawa (ozone-sensitive) parents used as checks. The population exhibited a wide range of foliar injury in response to the ozone treatment. Assessment of the data has begun for mapping ozone response genes.
A preliminary salt screening was performed on ~200 random inbred lines in North Carolina to optimize for growth system, salt treatment concentrations, application methods, and scoring. This preliminary screen was performed in order to become familiar with the pattern and timing of salt stress symptoms as they appear in this population. A full screening of the population for salt stress responses is being conducted during the fall of 2012.
Experimental plans and materials were prepared for aluminum screening of the population in North Carolina. Researchers with relevant experience were consulted and specialized equipment located. Growth chamber space is being reserved for conducting aluminum screening during July through December of 2012.
Initial phenotyping of the population for iron deficiency chlorosis was conducted during the summer of 2011 in Minnesota field trials by our University of Minnesota cooperator. Injury evaluations revealed good separation of the parents with Fiskeby III having a lower score than Mandarin (Ottawa). Variation for iron deficiency chlorosis injury is extensive within the population with scores for individual lines distributed throughout the complete range of injury scores from 1 to 5. The experiment is being repeated during the summer of 2012.
Excessive rain throughout the 2011 growing season prevented collection of wilting score data from the drought plots in Minnesota by our University of Minnesota cooperator. Seeds were harvested, processed and stored to ensure an adequate seed supply for remaining phenotyping studies. Drought tolerance evaluation of the population is being conducted in 2012, but success will depend on rainfall patterns providing drought conditions in Minnesota later in the season when canopy wilting can be accurately assessed.