Resistance to Stalk Rots in a Sorghum Diversity Panel.

Fusarium stalk rot and charcoal rot are the primary stalk rot diseases that cause significant yield loss in sorghum. Fusarium stalk rots (caused by Fusarium spp. including F. thapsinum, F. proliferatum, and F. andiyazi) are important when high temperatures and drought stress occur during grain filling followed by exposure to cooler and wetter conditions. However, charcoal rot (caused by Macrophomina phaseolina) occurs during prolonged post-flowering drought stress and does not require a period of cooler temperatures or higher moisture in order to manifest itself.  The diseases are important biotic constraints to sorghum production worldwide and are best managed through host plant resistance. A sorghum diversity panel, consisting of 300 accessions was evaluated to identify sources of resistance to stalk rot diseases. The accessions were evaluated in three environments (Manhattan 2011, Manhattan 2012 and Ottawa 2012) under artificial inoculation. A randomized complete block design with two replications was used. Adequate genetic variation for stalk rot resistance was observed in the sorghum diversity panel. Response to infection by stalk rot pathogens varied significantly among accessions and was not affected by botanical race and geographical origin. Out of a total of 300 accessions evaluated some 95 accessions were found to have resistance to Macrophomina phaseolina and 77 to Fusarium thapsinum. Of these, 53 accessions were resistant to both pathogens. These accessions with dual disease resistance will be useful in sorghum stalk rot resistance breeding programs.