Conversion of Alien Sorghums to Early Combine Genotypes¹

Abstract

Alien sorghums from the world collection of sorghums are being converted to early, combine‐height strains adapted, to the United States and other temperate areas. Conversion is being accomplished by a crossing and backcrossing program in Puerto Rico under favorable shortday photoperiods during the winter, with selection for early, short genotypes within segregating populations in Texas under long‐day conditions during the regular growing season.After 2½ years of work on the conversion program, the procedure has proved workable, with only minor changes in time of seeding. Data indicate that the majority of alien strains used segregate for three to four height or maturity genes when crossed to a 4‐dwarf early line.

Duplicate and Conquer: Multiple Homologs ofPHOSPHORUS-STARVATION TOLERANCE1Enhance Phosphorus Acquisition and Sorghum Performance on Low-Phosphorus Soils

“…Tropical converted accessions were produced by introgressing genomic regions conferring early maturity and dwarfing genes from an elite donor into exotic accessions (Stephens et al, 1967) and were selected to broadly represent the genetic diversity of cultivated sorghum (Sorghum bicolor). The breeding accessions included photoperiod-insensitive elite inbreds, improved cultivars, and landraces that either have been or are still used extensively in the United States and Brazil for sorghum breeding (Casa et al, 2008).…”

Efficient Mapping of Plant Height Quantitative Trait Loci in a Sorghum Association Population With Introgressed Dwarfing Genes

“…In brief, this panel consists of 230 lines from the sorghum conversion program (SC lines), and 148 ''elite'' lines, which actually constitute not only elite lines from public breeding programs, but also assorted lines of genetic and historical interest, many of which carry SC lines in their pedigrees. SC lines were developed from tall, exotic sorghum lines by crossing to a four-dwarf, elite donor line (BTx406), selfing, and selecting for short, early segregants suitable for combine harvest; the process of backcrossing to the exotic, selfing, and selecting was performed an average of four times for each SC line (Stephens et al 1967). Sorghum lines were phenotyped for six plant architectural traits in three replicates in Lubbock, TX in 2006: total plant height, preflag leaf height, preflag-to-flag leaf interval, distance from flag leaf to apex, rachis length, and panicle branch length (see Figure 1).…”

“…Briefly, the panel consists of 377 inbred lines for which population structure was estimated with 47 unlinked SSRs. Sixty percent of the panel is composed of sorghum conversion (SC) lines, which are short, early-flowering lines developed from tall, photoperiod-sensitive exotics through the introgression of dwarfing and photoperiod-insensitivity alleles from a common donor (Stephens et al 1967). The remaining 40% of the panel consists of elite grain and forage lines, and lines of genetic and historical importance.…”

Análise da estrutura populacional e do desequilíbrio de ligação de um painel de acessos de sorgo: uma abordagem usando teoria da coalescência

“…Além disso, essas cultivares precisam mostrar resistência ou tolerância a certos fatores bióticos, tais como doenças e pragas, e fatores abióticos, tais como altas temperaturas e estresse hídrico (condições de seca). Ainda, é preciso mostrar qualidade nutricional para atender às exigências das alimentações humana e animal (Singh and Lohithaswa, 2006 (iv) implementação da produção de sementes híbridas de 1946 até os dias de hoje; e (v) conversão de acessos tropicais exóticos de maturação tardia e alta estatura (sensíveis ao fotoperíodo) em acessos temperados de ma-turação precoce e baixa estatura a partir de 1963 (Stephens et al, 1967;Quinby, 1974;Rosenow et al, 1983;Klein et al, 2008), de forma a introduzir variabilidade exótica de genótipos tropicais produtivos no germoplasma temperado (Stephens et al, 1967;Casa et al, 2008). O uso deste germoplasma é utilizado até os dias de hoje no melhoramento, e cada uma dessas etapas exerceu grande influência na produção de sorgo nas regiões semi-áridas do mundo (Klein et al, 2008).…”

“…A conversão de acessos tropicais em acessos temperados, conhecida como SCP (Sorghum Conversion Program) (Stephens et al, 1967), foi uma estratégia importante estabelecida pelo USDA (United States Department of Agriculture) em colaboração com a Texas University (Casa et al, 2008). Em linhas gerais, vários cruzamentos envolvendo cultivares tropicais (não-adaptadas) e temperadas (adaptadas) foram realizados, e os indivíduos das populações obtidas foram submetidos a vários ciclos de retrocruzamentos com as cultivares tropicais (Rosenow et al, 1997).…”