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Breeding yanninicum subclovers w1th improved clover scorch resistance

G.J. Mitchell, M.L. Stanley and M.J. Cooper

S.A. Department of Agriculture G.P.O. Box 1671, Adelaide, S.A., 5001.

Clover scorch (Kabatiella caulivora) is the most damaging disease of subterranean clover in southern Australia (1). Trikkala, the most widely grown yanninicum subclover cultivar in Australia, is recommended for soils prone to waterlogging yet has only moderate resistance to this disease. A breeding programme established by Dr. P. Beale aims to develop new yanninicum subclovers with: better resistance to clover scorch than Trikkala, better winter growth than Trikkala, and a range of maturities.

Methods

Experimental lines and selected cultivars were sown in plots in four trials between 1985 and 1987 (1) the swards were evaluated for clover scorch resistance using a 0 to 10 scale (2) where 0=no disease and 10= complete death of clover.

Shortlisted lines were sown in three trials (Kangaroo Island - 1986 - plots 2.5 m x 1 m; Mt. Barker - 1988 - plots 5 m x 3 m; Keith - 1988 – plots 5m x 3 m ). All three trials involved four replicates per line. Dry matter (DM) production data was derived from cuts using a lawn mower. Cuts were taken on the folllowing dates (Kang. Is. on 17-9-86, 16-10-86 and 25-ll-86; Mt.Barker on 24-8-88 and 26-10-88; Keith on 16-9-88).

Another trial, involving plots l m with four replicates was sown in 1987 on Kangaroo Is. to assess the relative flowering times of lines. Days to first flower was measured as the period from sowing until at least ten plants each possess three open flowers for each plot.

Results and discussion

Seven lines with a range of maturities have been shortlisted for further evaluation. In field trials lines FS20 and FS24 have consistently shown greater resistance to clover scorch than Trikkala and have tended to produce more dry matter in the establishment year (Table 1).

Table 1 Clover scorch resistance and 1st year dry matter production for yanninucum subclovers

Trials are continuing to assess the performance of these experimental lines alongside other yanninicum lines from the NSCIP at sites throughout southern Australia.

1. Beale P.E. and Dube A. 1977. Fact Sheet 134/77 (S.A. Dept. Agric).

2. Beale P.E. and Crawford E.J. 1975. Agricultural Record 2 54-59.

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