Location: Plant Science Research2013 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.
3. Progress Report:
The objective of this project is to map stress tolerance genes in soybean for five abiotic stress factors: drought, iron deficiency chlorosis, ozone, salt, and toxic soil aluminum. A mapping population of 240 recombinant inbred lines (RILs) has been developed from a cross between tolerant (Fiskeby III) and sensitive (Mandarin Ottawa) genotypes. Each RIL 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. The DNA marker data was developed into a linkage map for this population. Programming code for the quantitative trait loci (QTL) analyses was been written for R/QTL and applied to the data collected for ozone-induced foliar and specific leaf weight. Significant QTLs for ozone response were identified on chromosomes 1 and 18. A significant QTL for specific leaf dry weight was also identified on chromosome 20. Preparation of an ozone manuscript has begun. Screening the population for salt stress in the greenhouse was completed using foliar injury, shoot biomass reduction, and sodium accumulation in tissues as assessments. Preliminary analysis of foliar Na+ indicated that this is a promising method for quantitative phenotyping of this trait. Salt-induced injury data was formatted and is ready for summary statistics and QTL analysis when the complementary biomass and sodium data becomes available. Screening the population for aluminum response was begun using a hydroponics approach. Approximately 40% of the RILs have been tested. Roots are being collected and stored in ethanol for later imaging and digital analysis to assess root system response to aluminum. Screening the population for iron deficiency chlorosis in Minnesota field plots was completed. Data from 2011 and 2012 are being analyzed in preparation for QTL analysis. Data from both 2011 and 2012 showed significant segregation within the population. Data are being analyzed and formatted for QTL analysis. Programming code for the QTL analyses written for R/QTL to conduct ozone analysis is being adapted for iron deficiency chlorosis. Weather permitted collection of wilting scores in Minnesota field plots during the summer of 2012, so screening of the population for drought was begun. Wilting scores were collected on two dates (July 5 and July 16) before rain events and confounding differences in maturity prevented further readings. On a scale of “1” (no wilting) to 5 (dead plant), scores for the tolerant Fiskeby III parent ranged from 1-2 and the scores for the sensitive Mandarin (Ottawa) parent ranged from 3-4. The RILs had scores that ranged from 1-4, suggesting that identification of QTL for drought in this population will be possible. Seed from the early maturing lines in the population were harvested from Minnesota field plots to maintain seeds supplies. ADODR monitoring: The project was monitored by email and telephone calls with the management staff representing the United Soybean Board.