Predicting heterosis in grain sorghum [Sorghum bicolor (L.) Moench] hybrids using sequence-based genetic similarity estimates

Authors: CROSIER, DANIEL - Texas A&M University; HOFFMANN, LEO - Texas A&M University; KLEIN, PATRICIA - Texas A&M University; Klein, Robert - Bob; ROONEY, WILLIAM - Texas A&M University

Submitted to: Journal of Crop Improvement
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/24/2020
Publication Date: 4/2/2020
Citation: Crosier, D., Hoffmann, L., Klein, P., Klein, R.R., Rooney, W. 2020. Predicting heterosis in grain sorghum [Sorghum bicolor (L.) Moench] hybrids using sequence-based genetic similarity estimates. Journal of Crop Improvement. https://doi.org/10.1080/15427528.2020.1748152.
DOI: https://doi.org/10.1080/15427528.2020.1748152

Interpretive Summary: The yield potential in grain sorghum hybrids has increased at a slower rate than other cereal crops including its close relative maize. While there are many reasons for this lag, increasing hybrid performance through broadening the genetic distance between parents is commonly hypothesized as a way to boost the rate of gain. To address this issue, we examine the correlation between the genetic similarity between sorghum parental lines and the performance of their hybrid offspring. This study will provide the necessary knowledge to breeders who work to exploit genetic diversity in improving grain yield of hybrid cereal crops including sorghum.

Technical Abstract: The genetic yield potential in grain sorghum hybrids has increased at a slower rate than other cereal crops including its close relative maize. 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. As such, the purpose of this study was to determine if genetic similarity in a set of elite sorghum inbred lines is correlated with heterosis or hybrid performance. To access the relationship between heterotic groups in sorghum, a panel of 436 inbred lines from the Texas A&M program were genotyped using Genotype by Sequencing (GBS). Principle coordinates analysis divided the lines into three groups through k-means clustering based on genetic similarity. Distinct groups of B lines, R lines, and forage lines were observed; however, marked diversity between the functional groups was not observed which may reflect interbreeding foundational sorghum accessions and the constraints placed on line development by CMS (cytoplasmic male sterility) hybrid production system. A mini core, twenty-four elite grain-type lines, was chosen and crossed to produce fifty-two hybrids, which were then evaluated along with the parental lines 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. While, the performance of select parental inbreds was predictive of hybrid performance, GBS-based genetic similarity was not a good predictor of heterosis or hybrid performance amongst elite Texas sorghum inbreds.