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EVALUATION OF TRIFOLIUM SUBTERRANEUM SSP. BRACHYCALYCINUM IN SOUTH AUSTRALIA, NEW SOUTH WALES AND QUEENSLAND.

C.T. de Koning1, G.A. Sandral2, B.S. Dear2, G.M. Lodge3, D.L. Lloyd4 , P.G.H. Nichols5 and N.S. Schubert 1

1South Australian Research and Development Institute, - Rosedale, SA, 5350
2
NSW Agriculture, - Wagga Wagga, NSW, 2650
3
NSW Agriculture, – Tamworth, NSW, 2340
4
Queensland Department of Primary Industries, - Toowoomba, QLD, 4350
5
Agriculture Western Australia, - Perth, WA, 6014

Abstract

In a series of trials conducted in South Australia, New South Wales and Queensland 12 ssp. brachycalycinum accessions were tested over 3 years to identify more productive and persistent types for low or erratic rainfall environments with slightly acid to alkaline soils. Seedling recruitment, dry matter production and seed reserves were measured over this period. The results were compared to the control cultivar Rosedale and suggest that large adaptation advantage exist for accession BE011 which was consistently superior across different state environments. BE011 produced on average 34% more dry matter and 27% higher seedling populations than the existing cultivar Rosedale.

Keywords: Trifolium subterraneum ssp. brachycalycinum, Rosedale, Clare, subclover.

Trifolium subterraneum ssp. brachycalycinum is a relatively under-developed subspecies of subterran-ean clover (1, 2, 3, 4, 5). There are only two commercial cultivars which have been developed in Australia (Clare and Rosedale) and a further two have been developed overseas (eg. Nuba and Antas). Clare does not persist well under frequent cropping and/or where the growing season is short . Clare is also soft seeded and can also lose substantial amounts of seed through false starts to the growing season. Rosedale was selected to extend subterranean clover into drier cropping - livestock regions (ie. 400 – 480 mm) which have slightly acid to alkaline pH soils. However, since the release of Rose-dale, it has been inconsistent in its performance and has lost favour with some farmers. Therefore, the aim of this study was to find new ssp. brachycalycinum cultivars with similar or earlier maturity to Rosedale that would provide more dry matter through a succession of seasons. The cohort established comprised of overseas introductions with early to mid-season maturity and hard seed levels higher than Clare, with some lines having similar levels of hard seed to that of Rosedale. The potential area in South Australia, New South Wales and Queensland for this ideotype is 1.8 million hectares. This paper will report on the progress and success of this cohort.

Materials and methods

A cohort consisting of 12 (BE001 - BE012) overseas ssp. brachycalycinum introductions was selected based on maturity and hard seededness. During 1995 this cohort entered the final field testing stage in South Australia (3 sites), southern New South Wales (2 sites), northern New South Wales (2 sites) and southern Queensland (1 site). Enough seed was provided to sow plots at 8 kg/ha. The Queensland site was re-sown in 1996 due to poor seasonal conditions in 1995. Trials were managed by the state collaborators. Trials in South Australia and southern NSW were not fenced so they were treated like the remainder of the farmer's paddock.

Measurements were made on seedling numbers in the establishment year and subsequent regeneration years, dry matter yields in winter/spring and seed reserves. Additional measurements were made, however, these will not be reported in this paper. The data is presented as mean values across all sites and then expressed as a percentage of Rosedale (Rosedale set at 100%). All of the data will be analysed in 1998 using spatial and multi-environment analyses.

Trials are nearing completion and promising lines will be recommended for registration during 1998.

Results

Seedling density

Seedling establishment numbers from the first and regeneration years for 1996 and 1997 are shown in Table 1. The ssp. brachycalycinum accessions BE010 and BE011 (126% and 127%, respectively, compared to Rosedale) had the highest recruitment numbers of all the BE accessions . The commercial cultivars Seaton Park and Dalkeith had higher plant numbers (152% and 151% respectively), which may be explained by their lower levels of hard seed (Tables 1 and 3). The poor recruit-ment observed in BE003 and BE004 was largely explained by poor seed reserves.

Dry matter production

Five of the twelve BE accessions had higher dry matter production than Rosedale when averaged across all sites. The lines BE001, BE009 and BE011 had the greatest production (147%, 129% and 134%, respect-ively). Lines BE002 and BE010 were marginally better than Rosedale (106% and 104%, respectively). The commercial cultivar Clare had greater dry matter pro-duction than Rosedale, the cultivar Seaton Park was only marginally better than Rosedale.

Seed production

Rosedale was the highest seed producer meaned over all sites. In southern New South Wales trials the line BE002 (108%) and Dalkeith (122%) were the only two genotypes to out produce Rosedale.

Performance by region

The overall comparison takes into account seedling density, dry matter production and seed yield. This com- parison shows that the accessions BE001, BE009, BE010 and BE011 were ranked the overall best performers (Table 1). The cohort's performance across environments is generally consistent when the top BE access- ions from each state are examined (Table 2).



Discussion

The accessions BE001, BE009, BE010 and BE011 are the top performing lines. BE001 will not be chosen as a Rosedale replacement due to its late maturity (BE001 has similar maturity to Clare). BE011 would be a strong contender to replace Rosedale, it has similar maturity to Rosedale (SA and WA flowering data, Table 3). In northern NSW, BE011 (112 days) flowers later than Rosedale (100 days). Hardseededness of BE011 is generally lower than Rosedale, which may favour BE011 in phased farming systems. Possibly Rosedale is too hard seeded for regular recruitment of seedlings and may be better suited to 1:1 pasture crop rotations. BE010 may also be a suitable replacement for Rosedale. Based on WA and SA flowering data the line BE009 flowers at least 10 days earlier than Rosedale and has superior dry matter production, as a result it may be valuable as an earlier flowering ssp. brachycalycinum cultivar. In addition, BE009 has high resistance to Red Legged Earth Mite at the seedling stage and similar hard seed levels to Rosedale. BE009 would be suited to frequent cropping systems.

Acknowledgments

Financial support for this project was provided by Australian Woolgrowers through the International Wool Secretariat (IWS) and Australian Grain growers through the Grains Research and Development Corporation (GRDC).

References

1. Archer, K.A. 1987a. NSCIP Workshop 1987.

2. Archer, K.A. 1987b. Proc. 4th Aust. Agron. Conf., Melbourne, Vic. p. 166

3. Collins, W.J. and Stern. W.R. 1987. In "Temperate Pastures - their production, use and management". Edited by J.L. Wheeler, C.J. Pearson and G.E. Robards. Aust. Wool Corp./CSIRO. pp. 276 - 278.

4. Dear, B.S., Cregan, P.D. and Hochman, Z. 1987. In "Temperate Pastures - their production, use and management". Edited by J.L. Wheeler, C.J. Pearson and G.E. Robards. Aust. Wool Corp./CSIRO. pp. 55 - 57.

5. Francis, C.M. and Gladstones, J.S. 1983. In "Genetic Resources of Forage Plants". Edited by. J.G. McIvor and R.A. Bray. CSIRO, Australia. pp. 251-260.

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