Evaluation of sorghum germplasm used in US breeding programmes for sources of sugary disease resistance uri icon

abstract

  • Ergot or sugary disease of sorghum has become an important constraint in North and South American countries thatrely on F1 hybrid seeds for high productivity. The objective of this research was to determine the vulnerability ofvarious germplasm sources and publicly bred sorghum lines to sugary disease (Claviceps africana) in the UnitedStates. Flower characteristics associated with sugary disease resistance were also studied. A-/B-line pairs, R-lines,putative sources of resistance and their hybrid combinations with an A3 cytoplasmic male-sterile source wereevaluated using a disease incidence, severity, and dual-ranking system. Trials were planted in a randomized completeblock design with three replications and repeated in at least two planting dates. Planting dates and pedigrees hadsignificant effects on overall ranking for resistance. A-lines were most susceptible to sugary disease. R-lines weremore susceptible than B-lines with respect to incidence and severity of the disease. Newer releases of A- and B-lineswere more susceptible to sugary disease than older releases. Sugary disease reaction of A-lines was a good indicator ofdisease reaction of B-lines. Tx2737, a popular R-line, was highly susceptible to sugary disease in spite of being a goodpollen shedder because the stigma emerged from glumes 2±3 days before anthesis. The combination of flowercharacteristics associated with resistance were least exposure time of stigma to inoculum before pollination, rapidstigma drying after pollination, and small stigma. An Ethiopian male-fertile germplasm accession, IS 8525, had goodlevels of resistance. Its A3 male-sterile hybrid had the highest level of resistance in the male-sterile background. IS8525 should be exploited in host-plant resistance strategies

publication date

  • 2001
  • 2001