Predicting heterosis in grain sorghum hybrids using sequence-based genetic similarity estimates

ABSTRACT

The genetic yield potential in grain sorghum [Sorghum bicolor (L.) Moench] hybrids has increased at a slower rate than other cereal crops. While there are many reasons for this lag, increasing heterosis through broadening genetic distance between parents is commonly hypothesized as a mechanism to boost the rate of gain. To assess the relationship between heterotic groups in sorghum, a panel of 435 inbred lines from the Texas A&M program was genotyped using Genotyping-By-Sequencing (GBS). Lines were divided into three groups through K-means clustering based on genetic similarity. Distinct groups of B-lines, R-lines, and forage lines were observed, but they were not highly divergent from one another. In both elite germplasm and a large panel of sorghum lines, less diversity was observed among B-lines than R-lines. From the panel of 435 inbreds, a subset of 24 elite grain-type lines was chosen and crossed to produce 52 hybrids. Hybrids and parental lines were evaluated in four environments for grain yield, plant height, days to flower, and panicle exsertion. Genetic similarity among elite inbred parents of hybrids evaluated ranged from 0.632 to 0.792. For all traits, significant mid-parent heterosis was observed; however, correlations between mid-parent heterosis and genetic similarity were low to non-significant. GBS-based genetic similarity is not a good predictor of heterosis or hybrid performance among elite Texas A&M sorghum inbreds. However, some parental-inbred performance measurements may be predictive of hybrid performance.

KEYWORDS:

• Genetic distance
• genotyping-By-Sequencing
• heterotic groups
• mid-parent heterosis
• single nucleotide polymorphism

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors acknowledge the United Sorghum Checkoff Program (grant # C1001-12) for the support of this work.