Survival of Claviceps africana Within Sorghum Panicles at Several Texas Locations.

Abstract

Survival of the sorghum ergot fungus, Claviceps africana, based on pathogenicity of recovered macroconidia used to inoculate sorghum (Sorghum bicolor), was measured in 2000 over the course of the year at five locations in Texas representing three climates. The experiment was repeated in 2001. Sphacelia associated with infected sorghum panicles were placed in nylon mesh bags and either buried at a 10-cm depth, placed on the soil surface, or suspended 61 cm above the ground. Samples were recovered after 4, 8, and 12 months and assessed for pathogenicity of surviving macroconidia by macerating tissue in water and spraying it onto panicles of flowering male-sterile sorghum in the greenhouse. Survival of ergot macroconidia in recovered panicles declined at all locations after the first 4 months that panicles were left in the field. The decline in viability during this period was greater in 2001 than in 2000. In 2000, survival after 4 months was greatest at Lubbock and Bushland, which have a continental steppe climate, than at the other three Texas locations, Weslaco and Corpus Christi, which have a subtropical subhumid climate, and College Station, which has a subtropical humid climate. However, this difference in survival was not as pronounced in 2001. Additionally, after 8 months, survival levels at all locations were similar. At the end of 12 months, infective macroconidia were found only at Lubbock in 2000, and only at Lubbock and College Station in 2001. Ergot macroconidia can survive in all major sorghum production areas of Texas; thus, conidia would not need to move long distances in order to initiate an epiphytotic.