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The use of wild wheats to increase potential grain number per head in hexaploid wheat

S.E. Knights and G.M. Halloran

School of Agriculture and Forestry. The University of Melbourne.
Parkville, Victoria, 3052.

The aim of this study was to see whether the developmental processes in ancestral Triticum species differed from those in commercial wheat. The possibility was explored that potentially higher spikelet number might be incorporated in commercial. hexaploid. wheat from such species to increase grain yield.

Methods

The durations and rates of development of five accessions of T. monococcum and two accessions of T. timopheevi were compared with those of three commercial cultivars, T. nestivum. All plants were vernalized for six weeks and then transplanted into pots containing soil on the 12 July 1992 and grown in a glasshouse. There were 4 replications of 40 plants per accession and the pots were arranged in a randomized block design. One plant per accession in each replicate was sampled and examined under a dissecting microscope at 2-3d intervals from transplanting to determine the stage of development of the apex of the primary tiller. The leaf initiation phase was defined as the period from sowing to double ridge, the spikelet initiation phase from double ridge to terminal spikelet initiation and the culm elongation phase from the commencement of elongation (i.e when the culm was >0.4 cm) to when it ceased. Hourly temperatures were recorded in the glasshouse on a datalogger and a base temperature of 0C was used for calculating thermal time. Durations of the phases were measured in thermal time. Rates of development through the phases were determined by simple linear regression of the number of primordia or the length of culm produced in the phase against thermal time. Development was also monitored by regular photographs of shoot apices under a scanning electron microscope.

Results and discussion

The hexaploid wheats developed much faster than accessions of both of the wild wheat species (Table 1).

Table 1. Rates and Durations of development phases of ten wheat accessions

aValues in columns followed by the same letter are not significantly different (P..0.05)

Table 2. Final measurements on the main tiller

The T. monococcum accessions achieved significantly higher spikelet number per head than the other accessions (Table 2). The spikelet initiation rates for the accessions of T. monocoecum were not significantly different from the hexaploid wheats (Table 1). T. monococcum achieved the high spikelet number through a longer duration of spikelet initiation than the hexaploid wheats. This development characteristic may be useful in late maturing wheats.

Acknowledgements

This work was funded by Grains Research and Development Corporation grant number UM32C

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