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ARS Home » Southeast Area » Stoneville, Mississippi » Crop Genetics Research » Research » Publications at this Location » Publication #295098
Title: Maturity effects on colony-forming units of Macrophomina phaseolina infection as measured using near-isogenic lines of soybeans

Author
item Mengistu, Alemu
item Ray, Jeffery - Jeff
item Smith, James - Rusty
item Boykin, Deborah

Submitted to: Journal of Crop Improvement
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/19/2013
Publication Date: 1/13/2014
Citation: Mengistu, A., Ray, J.D., Smith, J.R., Boykin, D.L. 2014. Maturity effects on colony-forming units of Macrophomina phaseolina infection as measured using near-isogenic lines of soybeans. Journal of Crop Improvement. 28:38-56.

Interpretive Summary: Charcoal rot fungus causes significant yield losses in soybean production in the US and as well in many other countries around the world. The effect of maturity on the severity of charcoal rot is not well understood mainly because maturity is generally confounded with genotypic background. Therefore field experiments using the two sets of near isogenic lines from either cultivar Clark or Harosoy, differing only by genes for maturity, were established on two soil types (sandy loam and clay) and evaluated for two years (2008 and 2009) in Stoneville, MS. Disease severity, expressed as colony-forming units of the fungus, was evaluated for each line at physiological maturity (soybean growth-stage R7). There was little evidence of a relationship between soybean maturity and disease severity within the maturity lines tested. Further, disease severity in both types of soils were similar, indicating that disease severity ratings may be equally achieved on either sandy loam or clay soils.

Technical Abstract: Charcoal rot (Macrophomina phaseolina) causes significant yield losses in soybean [Glycine max( L.) Merr.] production worldwide. The effect of maturity on the severity of charcoal rot is not well understood mainly because maturity is generally confounded with genotypic background. Therefore, the relationship between maturity and disease severity was examined using two sets of soybean lines derived from either cultivar Clark or Harosoy that were nearly-isogenic except for maturity genes. Field experiments using the two sets of NIL were established on two soil types (sandy loam and clay) and evaluated over two years (2008 and 2009) in Stoneville, MS. Disease severity, expressed as colony-forming units (CFU) of M. phaseolina, was evaluated for each line at physiological maturity (soybean growth-stage R7). Within a year, similar levels of disease severity were observed on both soil-types. Regression analysis indicated no significant (P < 0.05) relationship between maturity and CFU for either set of NIL on either soil type in either year. To investigate the potential effect of environment on the maturity-CFU relationship, environmental variables (rainfall, temperature, etc.) were added as covariates in the regression analysis. For both the sandy loam and clay soils in 2008, no environmental variable accounted for 10% or more of the variation in the relationship between maturity and CFU. However, in 2009 rainfall accounted for 17% of the variation found in the sandy loam soil and the minimum soil temperature (at the 5 cm depth) accounted for 25% of the variation found in the clay soil. Nonetheless, inclusion of these and other environmental variables as covariates in the model only allowed the detection of a significant relationship between maturity and CFU in the 2009-Clay environment (P = 0.0306, F = 6.00). Our results indicate that there was little evidence of a relationship between soybean maturity and disease severity within the maturity isolines tested. Our data further indicate that disease severity in both types of soils were similar indicating that successful disease severity ratings may be equally achieved on both sandy and loam soils.