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Influence of the gibberellin-sensitive Rht8 dwarfing gene on leaf epidermal cell dimensions and early vigour in wheat (Triticum aestivum L.)


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Botwright, TL, Rebetzke, GJ, Condon, AG and Richards, RA 2005 , 'Influence of the gibberellin-sensitive Rht8 dwarfing gene on leaf epidermal cell dimensions and early vigour in wheat (Triticum aestivum L.)' , Annals of Botany, vol. 95, no. 4 , pp. 631-639 , doi: 10.1093/aob/mci069.

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Background and Aims The gibberellin-insensitive Rht-B1b and Rht-D1b dwarfing genes are known to reduce the
size of cells in culms, leaves and coleoptiles of wheat. Resulting leaf area development of gibberellin-insensitive
wheats is poor compared to standard height (Rht-B1a and Rht-D1a) genotypes. Alternative dwarfing genes to
Rht-B1b and Rht-D1b are available that reduce plant height, such as the gibberellin-responsive Rht8 gene. This study
aims to investigate if Rht8 has a similar dwarfing effect on the size of leaf cells to reduce leaf area.
Methods The effect of Rht8 on cell size and leaf area was assessed in four types of epidermal cells (interstomatal,
long, sister and bulliform) measured on leaf 2 of standard height (rht8) and semi-dwarf (Rht8) doubled-haploid lines
(DHLs). The DHLs were derived from a cross between very vigorous, standard height (rht8) (‘Vigour18’) and less
vigorous, semi-dwarf (Rht8) (’Chuan-Mai 180) parents.
Key Results Large differences were observed in seedling vigour between the parents, where ‘Vigour18’ had a much
greater plant leaf area than ‘Chuan-Mai 18’. Accordingly, ‘Vigour18’ had on average longer, wider and more
epidermal cells and cell files than ‘Chuan-Mai 18’. Although there was correspondingly large genotypic variation
among DHLs for these traits, the contrast between semi-dwarf Rht8 and tall rht8 DHLs revealed no difference in the
size of leaf 2 or average cell characteristics. Hence, these traits were independent of plant height and therefore Rht8
in the DHLs. Correlations for leaf and average cell size across DHLs revealed a strong and positive relationship
between leaf width and cell files, while the relationships between leaf and cell width, and leaf and cell length were
not statistically different. The relative contribution of the four cell types (long, sister, interstomatal and bulliform)
to leaf size in the parents, comparative controls and DHLs is discussed.
Conclusions Despite a large range in early vigour among the DHLs, none of the DHLs attained the leaf area or
epidermal cell sizeandnumbersof the vigorous rht8 parent. Nonetheless, the potential exists to increase the early vigour
of semi-dwarf wheats by using GA-sensitive dwarfing genes such as Rht8.

Item Type: Article
Authors/Creators:Botwright, TL and Rebetzke, GJ and Condon, AG and Richards, RA
Keywords: Wheat, Triticum aestivum L., gibberellic acid, leaf epidermal cells, doubled-haploids, early vigour, leaf area, alternative dwarfing genes.
Journal or Publication Title: Annals of Botany
ISSN: 0305-7364
DOI / ID Number: 10.1093/aob/mci069
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