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Determinacy in cotton: measurement and potential implications

Milroy, S.ORCID: 0000-0002-3889-7058 and Bange, M. (2003) Determinacy in cotton: measurement and potential implications. In: 11th Australian Agronomy Conference: Solutions for a better environment, 2 - 6 February 2003, Geelong, Victoria


Cotton is an indeterminate species. However, the term ‘determinate’ is applied to cultivars that terminate reproductive development comparatively abruptly and do not readily begin a second fruiting cycle. It has been suggested that low determinacy may have agronomic benefit when intermittent stresses interrupt reproductive development. We developed two objective measures of determinacy. The first reflects the speed with which a cultivar approaches the point where dry matter is monopolised by developing fruit. The second reflects the outcome of this process in terms of the declining rate of node production relative to the rate at which flowers are exserted on successive nodes up the main stem. Both were correlated to the breeders’ subjective assessment of determinacy but were also strongly correlated to each other. It will be necessary to demonstrate the repeatability of this approach to assessing determinacy and to test its applicability under a range of conditions and with different groups of cultivars. Experiments to use these measures to explore whether low determinacy confers an advantage in conditions of intermittent drought stress, such as dry land cotton production, are underway.

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