Registration of 40 Converted Germplasm Sources from the Reinstated Sorghum Conversion Program

Forty sources of late-maturing sorghum [Sorghum bicolor (L.) Moench] germplasm registered with the National Plant Germplasm System as genetic stocks (Reg. No. GS-744, PI 674473 to Reg. No. GS-783, PI 674512) were converted to earlymaturing, dwarf-height BC1F3 families and released by the National Sorghum Foundation, the United Sorghum Checkoff Program, the USDA-ARS, and NuSeed/MMR Genetics in 2014. The sorghum working groups represented include zerazera, caudatum, conspicuum, durra, nandyal, nigricans, guineense, caudatum-kafir, caudatum-guineense, caudatum-nigricans, caudatum-durra, durra-kafir, durra-bicolor, caffrorumbicolor, and durra-dochna. Conversion was accomplished by crossing late-maturing tropical accessions to inbred BTx406 in a short-day nursery with selection of early-maturing, short genotypes within F2 segregating populations in a long-day nursery. Early-flowering short F2 selections were genotyped, and one F2 plant with the greatest proportion of the exotic genome from each accession was backcrossed to the plant introduction. The resulting BC1F1 was self-pollinated, and selections of early-maturing, short genotypes within BC1F2 segregating populations were made. Early-flowering, short BC1F2 selections were genotyped, and one BC1F2 plant with the greatest proportion of the exotic genome was selfpollinated. The BC1F2:3 families, RSC02-BC1-10-F3bk to RSC149BC1-12-F3bk, represent new sources of germplasm from the USDA-ARS sorghum collection readily usable in temperate zones worldwide.