Heterosis in lucerne testcrosses with Medicago arborea introgressions and Omani landraces and their performance in synthetics
J. A. G. Irwin A D , D. J. Armour A , P. M. Pepper B and K. F. Lowe CA School of Biological Sciences, University of Queensland, Qld 4072, Australia.
B Animal Research Institute, Agri-Science Queensland, Department of Employment, Economic Development and Innovation, Locked Bag 4, Moorooka, Qld 4105, Australia.
C Mutdapilly Research Station, Agri-Science Queensland, Department of Employment, Economic Development and Innovation, MS825, Peak Crossing, Qld 4306, Australia.
D Corresponding author. Email: j.irwin@uq.edu.au
Crop and Pasture Science 61(6) 450-463 https://doi.org/10.1071/CP10070
Submitted: 26 February 2010 Accepted: 23 April 2010 Published: 1 June 2010
Abstract
Testcrosses were made with novel sources of lucerne germplasm. These were evaluated in the field in a subtropical environment to identify the lines which produced the highest yielding hybrids as a guide to future breeding efforts. The novel sources were derivatives of Medicago sativa × M. arborea partial (asymmetric) hybrids (termed sac) and very highly winter-active Omani landraces of M. sativa. As testers, 2 lines were used; a Colletotrichum trifolii race 2 resistant selection from the group 9 Australian-bred and adapted cultivar PacL 901 (selection hereafter termed 901) and the Omani landrace, Oman 2, collected at 17°N latitude, from Salalah, Oman. In the row experiment, substantial and significantly positive tester parent heterosis for overall yield (sum of 13 harvests) was observed in all of the sac × Oman 2 testcrosses, with the mean performance of the 11 testcrosses (1839 g/m row) significantly (P < 0.05) exceeding the mean performance of the sac × 901 testcrosses (1703 g/m row) evaluated. Where 901 was used as the tester, heterosis values relative to the tester for the same sac lines were negative for all testcrosses with 8 of the testcrosses being significantly negative. For the Omani landrace × 901 testcrosses, positive and negative heterosis values for total yield relative to the tester were observed, but none were significantly different from zero. The 901 tester yielded significantly (P < 0.05) more per se than the Oman 2 tester (1956 v. 1470 g/m row), although in an adjacent sward experiment Oman 2 yielded comparably to most of the standard commercial cultivars.
The potential of the novel germplasm in the subtropics was verified in sward experiments with synthetics and/or strain crosses with yield increases of up to 42% over the benchmark synthetic Sequel. Further improvements can be expected following selection for disease and pest resistance within the lines and in the case of Oman 2 and sac, converging to maximise complementary gene action.
Additional keywords: alfalfa, arborea × sativa, heterosis, Omani landraces.
Acknowledgments
The authors gratefully acknowledge the funding provided by the GRDC, The University of Queensland, the A.W. Howard Trust and Agri-Science Queensland allowing conduct of this research; Dr E. T. Bingham, University of Wisconsin – Madison who developed the sac material used in this work and provided helpful advice; Dr Abdullah Al-Sadi, Sultan Quaboos University, Oman, for sourcing the Omani landraces; David Schofield and the staff of Gatton Research Station for the day-to-day management of the experiments; and Thomas Bowdler, Nikki Casey and Sandra Nolan for technical assistance.
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