Genetic Characterization of Harvest and Broom Quality Traits in Broomcorn.

Broomcorn (Sorghum vulgare var. technicum) is a type of sorghum specifically chosen for its utility in the broom-making industry.  Ideally, broomcorn lines have an extended panicle with the seed set congregated at the very end of the panicle.  The branches of the panicle would begin at the peduncle with minimal fusing of the central branches.  These varieties are well suited for mechanical harvesting, after which the seed is removed and the panicle straw woven into brooms.  The pedicels on the end of the straw act to capture dust particles while the thicker portion of the panicle provides support for the broom.  Broomcorn improvement at the University of Illinois over the past forty years has relied heavily on field breeding for desired harvest and broom quality traits.  Recent advancements in low cost genotyping technologies have enabled gene discovery and molecular breeding in broomcorn.  High throughput genotyping of 55 broomcorn cultivars that represent the available phenotypic variation generated high confidence single nucleotide polymorphisms (SNPs).  An Fst analysis of these SNPs assessed the genetic differentiation of the broomcorn sorghum types with traditional sweet and grain sorghum lines.  Additionally, phenotypes used to assess the “broominess” were collected for several hundred individuals across the 55 populations.  These traits include total panicle length, proportion of panicle with seed, yield per panicle, plant height, seed color, and a qualitative measurement of central branch fusion.  A genome-wide association study (GWAS) approach was used to identify loci that contribute to the variation observed in the broom quality and agronomic traits.  Further assessment of these loci can help to elucidate the genes involved in inflorescence architecture and could aid in the improvement of broomcorn lines through the use of marker assisted selection.