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Hardseededness and pattern of hard seed breakdown in Sardinian populations of Medicago polymorpha under field conditions

Published online by Cambridge University Press:  27 March 2009

C. Porqueddu ,
A. Loi  and
P. S. Cocks
C. Porqueddu
Affiliation:
Centro di Studio sul Miglioramento delta Produttivita' dei Pascoli, via E De Nicola, 07100 Sassari, Italy
A. Loi
Affiliation:
Centro di Studio sul Miglioramento delta Produttivita' dei Pascoli, via E De Nicola, 07100 Sassari, Italy Cooperative Research Centre for Legumes in Mediterranean Agriculture and Faculty of Agriculture, The University of Western Australia, Nedlands, WA 6009, Australia
P. S. Cocks
Affiliation:
Cooperative Research Centre for Legumes in Mediterranean Agriculture and Faculty of Agriculture, The University of Western Australia, Nedlands, WA 6009, Australia
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Summary

The hardseededness and pattern of hard seed breakdown of 35 accessions of Medicago polymorpha, collected in Sardinia, were compared with Circle Valley, an Australian cultivar, near Sassari, northern Sardinia. The seed was produced in three consecutive years (1991–93), and the hardseededness measured at intervals in trie field during the summer following its production. The results were related to previously measured pod characteristics that separated the varieties polymorpha and vulgaris

The variety polymorpha, which had been collected mainly from coastal regions, was harder seeded than the variety vulgaris, which had been collected mainly from cooler, inland regions. Wherever the origin, hardseededness levels remained > 85% even in the year when seed softening was greatest (1992). In other years means of 94% (1991) and 97% (1993) of seed remained hard in late September. In 1992 and 1993 most hard seed breakdown occurred between early August and early September, while in 1991 hard seed breakdown occurred in September itself. There was little difference between varieties in the pattern of hard seed breakdown. Seedling emergence was related to the amount of seed that became soft during the previous summer. The results also confirmed that hard seeds soften sequentially from the proximal end of the pod (nearest the calyx) to the distal end.

The Australian cultivar was one of the hardest seeded accessions, showing very little hard seed breakdown during the experimental period. This result highlights the importance of selecting pasture legumes under the conditions in which they are to be used: in Australia, cultivar Circle Valley usually loses some 20% of its hardseededness in the first year, comparable with the softest Sardinian accessions in Sardinia. Even among the Sardinian accessions, most were probably too hard seeded in 1993. Nevertheless it is likely that material in this experiment will be released as commercial cultivars for Sardinia and other similar environments in the Mediterranean basin.

Type
Crops and Soils
Information
The Journal of Agricultural Science , Volume 126 , Issue 2 , March 1996 , pp. 161 - 168
Copyright
Copyright © Cambridge University Press 1996

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