|YIN, XINHUA - University Of Tennessee|
|MCCLURE, ANGELA - University Of Tennessee|
|TYLER, DON - University Of Tennessee|
Submitted to: American Phytopathological Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 7/28/2015
Publication Date: 8/1/2015
Citation: Mengistu, A., Yin, X., Bellaloui, N., Mcclure, A., Tyler, D.D., Reddy, K.N. 2015. Potassium and Phosphorus effects on disease severity of charcoal rot of soybean. American Phytopathological Society Abstracts. 2015 APS Presentation Abstract 299-P.
Technical Abstract: The effects of potassium (K) and phosphorus (P) fertilizers on charcoal rot of soybean [Glycine max (L.) Merr.] are unknown. Therefore, the severity of charcoal rot was studied at five levels of K (0, 37, 75, 111 and 149 kg K ha-1) and a level that was equal to the recommended fertilizer application rate based on annual soil K testing; and five levels of P (0, 10, 20, 30 and 40 kg P ha-1) and a level that was equal to the recommended P fertilizer application rate based on annual soil testing under field conditions in 2008, 2009 and 2010 at Jackson and Milan, TN, USA. Analysis of variance showed no significant effect from treatments or treatment-by-year interactions. However, P but not K application had a significant effect on colony forming unit (CFU) of Macrophomina phaseolina extracted from soil. Analysis using treatment as a linear trend effect indicated that tissue CFU as a function of K rates showed a positive but non-significant slope at both Jackson (P=0.10) and Milan (P=0.08) in 2009, suggesting a modest increase in disease severity. Further increases in K rate however, resulted in a negative slope at Milan (P=0.08) in 2010. The CFU from soil also showed a similar positive significant slope (P=0.03) with P rate in Milan in 2009 and 2010 (P=0.10), but not for 2008. Our results showed that increasing either the K or P application rates over the recommended rates and control (0 Kg-1ha) did not affect the CFU of Macrophomina phaseolina.