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 early-maturing, 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, caffrorum-bicolor, 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 F-2 segregating populations in a long-day nursery. Early-flowering short F-2 selections were genotyped, and one F-2 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 self-pollinated. The BC1F2:3 families, RSC02-BC1-10-F-3 bk to RSC149-BC1-12-F-3 bk, represent new sources of germplasm from the USDA-ARS sorghum collection readily usable in temperate zones worldwide.