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Evaluating wheat and rapeseed genotypes in relation to environment

P.M. Bremner, J.L. Davidson, D.B. Jones and L.F. Myers

CSIRO, Division of Plant Industry, Canberra. A.C.T. 2601.

We are attempting to assess the production potentials for wheat and rapeseed in the temperate high rainfall zone where few crops are grown. Most of the information available from controlled environment studies suggests that both crops should be particularly suited to the cooler parts of the zone. Wheat, for example, has been reported by some workers as yielding best if temperatures during grain development are around 12-15C (e.g. Thorne et al. 1968; Warrington et al. 1977). These temperatures are several degrees lower than those generally measured in the wheat belt during grain development (Nix 1975) but do correspond with mean tablelands' temperatures during the long days of early summer. However, because of the fluctuations in conditions experienced by field crops and the prevalence of interactions between environmental parameters it is unlikely that results from controlled environments can be used to predict field responses with useful accuracy. Another limitation of controlled environment studies is that they are usually restricted to one or few varieties. For generalizations about the responses of crops to be valid they must be based on a range of genotypes that can be accepted as being representative of most varieties that are grown.

We plan to evaluate the potential of wheat and rapeseed through relating the yields of representative samples of each crop to different levels of temperature, radiation, daylength and water supply experienced in a range of field environments. The selection of genotypes for the representative samples is based on measured responses in time of ear emergence to vernalization and photoperiod in the glasshouse (Syme 1973). At the time of writing over 200 genotypes of wheat and 50 of rapeseed have been grown under long (16 h) or short (10 h) days with or without vernalization. With this screening study nearing completion, it is clear that the genotypes grown exhibit a broad spectrum of responses to vernalization and long days respectively. Wheat genotypes, for instance, vary from low low (e.g. Sunset, Siete Cerros) through low high (Federation, Opal) and high low (Priboy, Sadovo 1) to high high (Isis, Joleen). Genotypes still to head may have bigger responses. Certainly the range of responses measured across all varieties is much greater than that offered by the Australian wheats, which in general have relatively small responses to vernalization and substantial reponses to daylength.

Within each crop a sample of about 30 genotypes will be chosen to cover the measured range of responses. This should provide a sound basis for investigating the merits of different mechanisms of flowering control for wheat in different parts of the region.

We plan to vary growing conditions by sowing at several times at three sites, one warm coastal, and two cool tablelands. All are at about 35 latitude, and we would like to collaborate with agronomists in other centres who are concerned with similar objectives and who could extend the study over a greater range of latitudes and climates.

Nix, H.A. (1975). In 'Australian field crops. 1. Wheat and other temperate cereals. Ed. A. Lazenby and E.M. Matheson, Angus and Robertson.

Syme. J.R. (1973). Aust J. agric. Res. 24: 657.

Thorne, G.N., Ford, M.A. and Watson, O.J. (1968). Ann. Hot. 32: 425.

Warrington, I.J., Dunstone, R.L., and Green, L.M. (1977). Aust. J. agric. Res. 28: 11.

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