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Breeding for Herbicide Tolerance, Functional Diversity, and Leveraging Parent Hybrid Relationships in a Sorghum Breeding Program
Abstract
For sorghum to continue to remain a competitive crop, continual increases in yield need to be made. However, other traits such as abiotic stress tolerance, biotic stress tolerance, and most recently herbicide tolerance also warrant improvement. Implementation of genomic prediction, as was demonstrated herein, can bolster rates of genetic gain and permit more efficient allocation of resources within hybrid sorghum breeding programs. In the present study, modeling genotype-by-environment effects and including phenotypic data from parental lines significantly increased the prediction accuracy of genomic prediction models for hybrid grain sorghum. To make further genetic gain, maintaining or introducing additional genetic diversity into plant breeding programs is necessary; however, diversity at the cost of reduced performance is not sought by breeders. This study also evaluated (i) the performance of sorghum lines from backcross nested association mapping (BC-NAM) populations developed as part of the Germplasm Utilization & Enhancement of Sorghum Strategy (GUESS) program and (ii) the potential of genomic prediction to screen diverse lines from BC-NAM populations. Despite the diverse origins of the donor parental lines, many BC1 derived lines performed significantly better than the recurrent parent, R.Tx436. Moderate prediction accuracies were found for days to mid-anthesis, grain yield, and plant height showing that genomic prediction can be an efficient way of pre-screening lines prior to phenotypic evaluation. While it was necessary to have related lines in the training and prediction sets, training sets for genomic prediction models can be optimized in large BC-NAM populations with a relatively low fraction of individuals needing to be evaluated. Lastly, post-emergent grass weed control options in sorghum have historically been limited. In this study, mass selection was used to select for increased tolerance to a broad-spectrum herbicide (tembotrione). Over four cycles of selection for tembotrione tolerance, populations showed significantly more tolerance to tembotrione. Consistent and modest genetic gain was made over four cycles of selection, indicating both the quantitative nature of the trait and sufficient heritability to further improve the trait. Given further development, tembotrione-resistant sorghum hybrids could provide an effective means of post-emergent weed control for a range of common weeds.
Citation
Crozier, Daniel Shaw (2023). Breeding for Herbicide Tolerance, Functional Diversity, and Leveraging Parent Hybrid Relationships in a Sorghum Breeding Program. Doctoral dissertation, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /199936.