Development of Perennial Grain Sorghum

Stan Cox,Andrew Paterson,Pheonah Nabukalu,Shakirah Nakasagga,Wenqian Kong

doi:10.3390/su10010172

Stan Cox, Andrew Paterson + Show 3 more

Open Access

https://doi.org/10.3390/su10010172

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Abstract

Perennial germplasm derived from crosses between Sorghum bicolor and either S. halepense or S. propinquum is being developed with the goal of preventing and reversing soil degradation in the world’s grain sorghum-growing regions. Perennial grain sorghum plants produce subterranean stems known as rhizomes that sprout to form the next season’s crop. In Kansas, breeding perennial sorghum involves crossing S. bicolor cultivars or breeding lines to S. halepense or perennial S. bicolorn × S. halepense breeding lines, selecting perennial plants from F2 or subsequent populations, crossing those plants with S. bicolor, and repeating the cycle. A retrospective field trial in Kansas showed that selection and backcrossing during 2002–2009 had improved grain yields and seed weights of breeding lines. Second-season grain yields of sorghum lines regrowing from rhizomes were similar to yields in the first season. Further selection cycles have been completed since 2009. Many rhizomatous lines that cannot survive winters in Kansas are perennial at subtropical or tropical locations in North America and Africa. Grain yield in Kansas was not correlated with rhizomatousness in either Kansas or Uganda. Genomic regions affecting rhizome growth and development have been mapped, providing new breeding tools. The S. halepense gene pool may harbor many alleles useful for improving sorghum for a broad range of traits in addition to perenniality.

Highlights

Grain sorghum (Sorghum bicolor) ranks fifth among the world’s cereal crops in area sown
The process of breeding perennial grain sorghum begins with controlled hybridization between annual grain sorghum and either of two wild perennial grasses, S. halepense or S. propinquum
Sorghum halepense was the result of later natural hybridization between S. bicolor and S. propinquum followed by a spontaneous doubling of the chromosome number to 40

Summary

Introduction

Grain sorghum (Sorghum bicolor) ranks fifth among the world’s cereal crops in area sown. The process of breeding perennial grain sorghum begins with controlled hybridization between annual grain sorghum and either of two wild perennial grasses, S. halepense or S. propinquum. Perennial Sorghum species produce tillers and basal subterranean stems known as rhizomes. Wild perennial Sorghum species, the sources of genes for rhizome development, are poorly suited for agriculture. They produce large numbers of thin, flexible culms (stems) and small quantities of very small, hulled seeds that drop to the ground when ripe. In breeding perennial grain sorghum, it is first necessary to bring genes from grain sorghum that confer good grain-production traits into a common pool with genes from wild perennial species for rhizome development. That is accomplished by hybridizing the former with the latter to produce populations of plants that carry genes from both parents in various combinations

Establishment and Genetic Analysis of the Perennial Grain Sorghum Gene Pool

Findings

Procedure for Developing Perennial Grain Sorghum Germplasm