ARS | Publication request: A cut-stem inoculation technique to evaluate soybean for resistance to Macrophomina phaseolina

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 28, 2012
Publication Date: July 10, 2012
Citation: Twizeyimana, M., Hill, C.B., Pawlowski, M., Paul, C., Hartman, G.L. 2012. A cut-stem inoculation technique to evaluate soybean for resistance to Macrophomina phaseolina. Plant Disease. 96:1210-1215.

Interpretive Summary: Charcoal rot of soybean, caused by a fungal pathogen, is the leading soil borne disease in many states in the USA. Effective and reliable methods to evaluate soybean for resistance to this fungus are needed as part of a management scheme that would utilize host resistance. This study investigated the use of a cut-stem inoculation technique to evaluate soybean genotypes for resistance to this fungal pathogen. The cut-stem inoculation technique, which has several advantages over field tests, successfully distinguished differences in aggressiveness among isolates of the fungal pathogen and relative differences among soybean genotypes for resistance to the fungal pathogen that causes charcoal rot that were comparable to results of field tests. This information will be useful for soybean breeders, pathologists, and those interested in crop improvement because it provides information on how to evaluate soybeans for resistance to a disease where soybean cultivars for resistance are not available for soybean growers.

Technical Abstract: Charcoal rot of soybean is caused by the fungal pathogen Macrophomina phaseolina. Effective and reliable methods to evaluate soybean for resistance to this fungus are needed as part of a management scheme that would utilize host resistance. This study investigated the use of a cut-stem inoculation technique to evaluate soybean genotypes for resistance to M. phaseolina. The first experiment compared aggressiveness of M. phaseolina isolates collected from soybean on different soybean genotypes. Significant (P < 0.05) differences among the isolates and genotypes for relative area under disease progress curve (RAUDPC) were found without a significant isolate x genotype interaction. The second experiment compared 14 soybean genotypes inoculated with M. phaseolina in greenhouse and growth chamber trials. Significant (P < 0.05) differences among environments and highly significant (P < 0.001) differences among soybean genotypes for RAUDPC were found.The environment x genotype interaction was non-significant (P > 0.05). Genotypes DT97-4290, DT98-7553, DT98-17554, and DT99-16864 had significantly (P < 0.05) lower RAUDPC than seven of the 14 genotypes. The third experiment evaluated resistance in selected Phaseolus spp. genotypes. The P. lunatus cultivar Baby Bush Lima had significantly (P < 0.05) lower RAUDPC than P. vulgaris genotypes evaluated. The cut-stem inoculation technique, which has several advantages over field tests, successfully distinguished differences in aggressiveness among M. phaseolina isolates and relative differences among soybean genotypes for resistance to M. phaseolina comparable to results of field tests.