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Heterosis and the metabolism of gibberellin A20 in sorghum

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Abstract

The correlation between gibberellin (GA) metabolism and growth rate was investigated using two Sorghum bicolor inbred lines, Hegari and AT×623, and their heterotic F1 hybrid. Previous studies have demonstrated that this hybrid is taller and has substantially greater shoot dry weights and leaf areas than either parental inbred. [3H]GA20 was applied to the leaf whorl of seedlings and after 24 hours, plants were harvested and separated into roots, shoot cylinders containing the apical meristems, and leaf blades. Chromatographic analyses of metabolites indicated the conversions of [3H]GA20 to [3H]GA1,8 and 29. The conversion of [2H]GA20 to [2H]GA1 was demonstrated by gas chromatography-selected ion monitoring (GC-SIM). Putative glucosyl conjugates of all of the [3H]GAs were also produced and GA8 was identified by GC-SIM following enzymic cleavage of the putative [3H]GA8 glucosyl conjugate fraction. Comparing the genotypes, [3H]GA20 metabolism was more rapid in the shoot cylinders of the hybrid than in the shoot cylinders from inbreds. In the hybrid samples, there was a three-fold increase in the putative conjugate(s) of [3H]GA1 which was the principal metabolite, and increased production of [3H]GA8 and the putative conjugates of [3H]GA29 and [3H]GA8. Conversely, levels of the remaining precursor, [3H]GA20, and its putative conjugate(s) were reduced in the hybrid. The rate of GA20 metabolism was thus positively correlated with growth rate across these sorghum genotypes. This correlation supports a promotive role of GA in the regulation of shoot growth and in the expression of heterosis (hybrid vigor) in sorghum.

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  1. Department of Biological Sciences, University of Lethbridge, T1K 3M4, Alberta, Canada

    Stewart B. Rood

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Rood, S.B. Heterosis and the metabolism of gibberellin A20 in sorghum. Plant Growth Regul 16, 271–278 (1995). https://doi.org/10.1007/BF00024786

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  • DOI: https://doi.org/10.1007/BF00024786

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