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Poster: Biology & Disease Mgmt: Cultural Control


Reduced Macrophomina phaseolina colonization of soybean by supplementing with the secondary nutrients calcium and magnesium
T. WILKERSON (1), M. Tomaso-Peterson (2), B. Golden (3), A. Brown (4), T. Allen (3) (1) Mississippi State University, U.S.A.; (2) Mississippi State University, U.S.A.; (3) Mississippi State University Delta Research and Extension Center, U.S.A.; (4) Missi

Macrophomina phaseolina (Tassi) Goid (Mp) is a ubiquitous soilborne fungal pathogen that causes charcoal rot (CR) of soybean. Charcoal rot annually limits profitability, especially in years when hot and dry environmental conditions persist. Throughout the southern United States, CR consistently remains one of the top five soybean diseases and has resulted in an estimated 11 million metric ton reduction in yield over the past 20 years. The objective of this research was to reduce Mp colonization of field grown soybean by supplementing secondary nutrients, specifically calcium (Ca) and magnesium (Mg). In 2014 and 2015 non-irrigated, Mp-inoculated field trials were conducted with a CR-susceptible and a CR-moderately-resistant cultivar. Treatment applications consisted of 1,120 kg/ha rate of Ca and Mg alone and in combination at each of three timings: pre-plant, at plant, and pre-plant fb at plant. Control plots consisted of a completely non-treated non-inoculated in addition to an Mp-inoculated non-treated. Root samples were taken at the R3, R5, R7, and R8 growth stages. Colony forming units (cfu) were enumerated from ground, disinfested root tissue using a semi-selective medium. Reductions in cfus were observed to be approximately 35% in the moderately-resistant cultivar and a 45 to 50% reduction in the susceptible cultivar, compared to the non-treated. Reduction in colonization was observed in some cases although not across all treatments.