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Evaluating the Impact of a Trait for Increased Specific Leaf Area on Wheat Yields Using a Crop Simulation Model

^a CSIRO Plant Industry, Private Bag no. 5, Wembley, WA 6913, Australia
^b CSIRO Plant Industry, P.O. Box 1600, Canberra, ACT 2601, Australia

* Corresponding author (Senthold.Asseng{at}csiro.au)

Received for publication May 1, 2001. Early vigorous growth (also called early vigor) has been suggested as a characteristic to increase yields of wheat (Triticum aestivum L.) in rainfed environments. Breeders have tried to incorporate early vigor by selecting for increased specific leaf area (SLA). A crop simulation model (APSIM-Nwheat) was used to evaluate the role of SLA on potential yield. Increased early vigor was simulated by increasing the SLA trait in the model. Grain yields were simulated for the mediterranean climate of Western Australia with winter-dominant rainfall, for New South Wales with evenly distributed rainfall, and for Queensland with a subtropical climate with summer-dominant rainfall. Independent, multiseason simulations were performed with historical weather records. The largest average yield increase with greater SLA was 15% on the sandy soil in Western Australia but only with additional N inputs. In the low-rainfall region of Western Australia, with low N input, a yield increase of up to 5% was achieved on the sandy soil while yield responses were negative on the clay soil. With increased N application, the SLA trait increased yields by up to 7% on the clay soils in this region. The increased SLA trait failed to increase yields and even decreased yields on average in New South Wales and in Queensland, except in above-average rainfall seasons and only at high N application. Crop management, in particular crop nutrition, is an important factor determining yield expression of new physiological traits and needs to be considered when evaluating traits.

Abbreviations: DOY, day of year • ET, evapotranspiration • LAI, leaf area index • PAW, potential plant available soil water-holding capacity in the potential maximum rooting zone • SLA, specific leaf area

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