Journal Article

Regulation of tillering in sorghum: genotypic effects

Hae Koo Kim, Delphine Luquet, Erik van Oosterom, Michael Dingkuhn and Graeme Hammer

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 106, issue 1, pages 69-78
Published in print July 2010 | ISSN: 0305-7364
Published online April 2010 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcq080
Regulation of tillering in sorghum: genotypic effects

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  • Ecology and Conservation
  • Evolutionary Biology
  • Plant Sciences and Forestry

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Background and Aims

Genotypic variation in tillering can be caused by differences in the carbon supply–demand balance within a plant. The aim of this study was to understand and quantify the effects of genotype on tillering as a consequence of the underlying internal competition for carbohydrates.

Methods

Five sorghum hybrids, derived from inbred lines with a common genetic background and with similar phenology and plant height but contrasting tillering, were grown in five experiments. The experiments covered a wide range in radiation and temperature conditions, so that number of tillers produced varied significantly. Data on leaf area, tiller number, and biomass accumulation and partitioning were collected at regular intervals. To quantify internal plant competition for carbohydrates, a carbohydrate supply–demand index (S/Dindex) was developed and related to variation in tillering.

Key Results

The appearance of main shoot leaves and tillers was highly co-ordinated across genotypes. High-tillering hybrids had a greater appearance frequency of early tiller ranks than low-tillering hybrids, and this was associated with narrower and hence smaller main shoot leaves. A generalized S/Dindex of internal plant competition accounted for most of the observed variation in maximum tiller number (Ntiller,max) across genotypes. However, genotypic differences in the relationship between the S/Dindex and Ntiller,max suggested that high-tillering hybrids also had a lower S/D threshold at which tillers appeared, possibly associated with hormonal effects.

Conclusions

The results support the hypothesis that genotypic differences in tillering were associated with differences in plant carbon S/D balance, associated with differences in leaf size and in the threshold at which tillers grow out. The results provide avenues for phenotyping of mapping populations to identify genomic regions regulating tillering. Incorporating the results in crop growth simulation models could provide insight into the complex genotype-by-management-by-environment interactions associated with drought adaptation.

Keywords: Carbohydrate supply–demand ratio; genotype-by-environment interaction; internal plant competition; leaf area development; leaf width; Sorghum bicolor; tiller number; tiller onset

Journal Article.  6003 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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