Registration of partially converted germplasm from 44 accessions of the USDA-ARS Ethiopian and Sudanese sorghum collections

Forty-four sources of late-maturing sorghum [Sorghum bicolor (L.) Moench] germplasm registered with National Plant Germplasm System as genetic stocks (Reg. No. GS-655, PI 665639 to Reg. No. GS-698, PI 665682) were converted to early-maturing, dwarf-height F₃ families and were released by the National Sorghum Foundation, the United Sorghum Checkoff Program, the USDA-ARS, and MMR Genetics in 2012. The sorghum working groups represented in these partially converted materials include zerazera, caudatum, caudatum-kafr, caudatum-guineense, caudatum-nigricans, caudatum-durra, nandyal, durra, durra-kafr, and durra-bicolor. Conversion was accomplished by crossing photoperiod-sensitive tropical accessions to elite line BTx406 during the winter in Puerto Vallarta, Mexico with selection of early-maturing, short (generally 2- or 3-dwarf) genotypes within F₂ segregating populations under long-day, summer conditions in Vega, TX. Early-flowering short F₂ selections were genotyped by sequencing, and five F₂ plants with the greatest proportion of the exotic genome from each accession were selfed in Puerto Vallarta. The resulting F_2:3 germplasm families, RSC02-3sel(bulk) to RSC149-3sel(bulk), represent new sources of germplasm from the USDA-ARS collection of a height and maturity readily usable to temperate-zone areas of the world. This germplasm will be useful in breeding programs by providing new genetic diversity from tropical accessions currently not available for use in hybrids.