Evaluation of sorghum waxy A1- and R-lines as hybrids

Abstract

The Waxy locus (Wx) encodes the granule-bound starch synthase enzyme, which synthesizes amylose, the long-chain, unbranched starch polymer. Loss of function alleles of Wx result in the endosperm having a waxy appearance, and contain nearly all amylopectin, the highly branched starch polymer. A critical question for commercialization of waxy grain sorghum [Sorghum bicolor (L.) Moench] for applications ranging from food industry to bioenergy crop production is whether hybrids deleteriously affect agronomic traits. A set of six waxy sorghum A-lines was crossed with a set of six R-lines developed by USDA-ARS in Lincoln, NE. The hybrids were grown in two field sites under dryland and irrigated conditions. Both agronomic and grain composition traits were determined. The amylose concentration from all waxy hybrid grain was around 5% compared to wild-type hybrid checks, which had concentrations around 35%. In general, seedling emergence, test weight, and 100-seed weight were lower for wx hybrids than the commercial check. The grain yields for wx hybrid combinations with A lines PI 670136 and PI 672150 (Wheatland wx) or R-line PI 672152 (RTx430 wx) were over 8000 kg ha⁻¹ for several combinations. The A line PI 670136 in combination with five of the R-lines evaluated produced white sorghum grain on tan plants that could be milled into food grade white sorghum flour. The waxy hybrids in this study illustrate the potential to commercially produce wx grain sorghum for a range of applications.