Start Date: Mar 21, 2007
End Date: Mar 20, 2012
1) Large-scale evaluations of the base collection through screening of the core (2,400 accessions), and the Sudan and Mali working (600 accessions) collections will be carried out. The core collection represents a random selection of the base collection. The Sudan and Mali working collections are accessions that breeders have selected based on agronomic performance and yield potential. Selected resistance sources will be screened over locations in different years to assess their horizontal disease resistance. 2) Two hundred fifty C. sublineolum single spore isolates collected over the past four years from various locations of the United States and Puerto Rico and are currently in long-term storage in the laboratory will be used. Host plant evaluations in the greenhouse will be conducted to establish the pathotypes of C. sublineolum. 3) Two closely related pathotypes of P. sorghi, P1 and P3, will be used to identify the differentially expressed unique sequences using standard AFLP technology as well as SSH. 4) A total of six cultivars, B1, BTx7078 and SC170-6-17 (susceptible lines), BTx635 (resistant line), SC140 and SC64 (their reaction to head smut is unknown), will be included in this study. Four inoculation methods--seed treatment, soil treatment, media placement, and syringe injection--will be employed. Four Texas isolates collected from College Station, Corpus Christi, Weslaco, and Beeville will be evaluated, with three replications for all four inoculation methods and all six cultivars simultaneously. In each replication, disease incidence (i.e., whether the inflorescence is replaced with sori or not) will be recorded.