Negative associations still exist between yield and fibre quality in cotton breeding programs in Australia and USA

This research demonstrates the negative association between cotton (Gossypium hirsutum L) yield and fibre quality (length, strength, micronaire, fineness and maturity) through time and on two continents. In Australia (AUS), six years of experiments with intermediate stage breeding material, selected on the basis of high quality were compared with eleven years of the USDA Regional High Quality Test (US), a component of the National Cotton Variety test. Stepwise linear regression was used to measure the association of quality with yield. Overall, fibre length and strength had significant (P<0.001) negative association with yield: fibre maturity had a positive association, while micronaire and fineness were inconsistent between years. The mean association for fibre strength in AUS data meant that a strength improvement from 314 to 333 kN m kg(-1), was associated with a yield reduction of 1000 kg lint/ha. Yields were greater in AUS than in US, so there were generally steeper slopes for US data describing the negative association between fibre length and strength with yield. This research confirms that a negative association still exists between fibre quality and yield and highlights breaking of linkage as one possible component of progress being made in decreasing this association. Suggested breeding strategies include selecting lines that are outliers with better fibre and yield and to use those lines in a recurrent selection program. It was concluded that large population sizes, robust testing and intermating of retained elite lines are required in early segregating generations to ensure the rare combinations of good fibre and yield can be increased and identified. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.