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12 May 2014 Phosphate responses of some Trifolium repens × T. uniflorum interspecific hybrids grown in soil
S. N. Nichols, J. R. Crush, L. Ouyang
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Previous studies in sand culture suggested that some white clover (Trifolium repens) × T. uniflorum interspecific hybrids were more tolerant than white clover of low external phosphate (P) supply. Here, P acquisition and growth responses were determined in soil for two T. repens × T. uniflorum backcross hybrids and their parental white clover cultivar, grown in a glasshouse pot experiment at Olsen P of 6, 7, 9, 14, or 20 mg P kg–1 soil. Growth of all of the clover entries responded strongly to increasing soil P levels, and one hybrid clover grew, on average, 17% better than the white clover control cultivar at Olsen soil P 9–20 mg kg–1. Internal P concentrations and shoot growth per unit P absorbed did not differ among the clovers. Instead, improved growth of the hybrid resulted from a greater ability to acquire soil P. This hybrid had the longest, most frequently branched roots. Frequent branching and growth of root tips into fresh soil would reduce the limitations to P uptake imposed by slow diffusion of P to the root surface. The results confirm previous observations that interspecific hybridisation is a useful strategy for increasing the range of P responsiveness in breeding populations for white clover.

© CSIRO 2014
S. N. Nichols, J. R. Crush, and L. Ouyang "Phosphate responses of some Trifolium repens × T. uniflorum interspecific hybrids grown in soil," Crop and Pasture Science 65(4), 382-387, (12 May 2014).
Received: 16 January 2014; Accepted: 1 April 2014; Published: 12 May 2014

interspecific hybridisation
phosphate acquisition
root branching
Trifolium uniflorum
white clover
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