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Variation in water-use efficiency and its correlation with carbon isotope discrimination in peanut cultivars grown in the field

G.C. Wrighta, K.T. Hubickb and G.D. Farquharb

aQueensland Dept. Primary Industries, P.O. Box 23, Kingaroy Q. 4610
Res. School Biol Sci. ANU, G.P.O. Box 475, Canberra, A.C.T., 2601

Improvement in water-use efficiency (WUE), defined as the ratio of dry matter production to water use, may help increase yield when water resources are limited. Genetic variation in WUE in peanut cultivars has been shown in pots (1), and WUE and isotope discrimination against 13C during CO2 assimilation, Δ, were negatively correlated as predicted on the basis of theory (see 2). This experimental confirmation of the relationship between WUE and A therefore supports the possibility of using Δas a criterion to exploit variation in W in breeding programmes, provided the pot results can be extended and verified under field conditions. This paper describes an experiment to assess variation in WUE among peanut cultivars growing in small canopies in the field.


A field experiment studying variation in WUE and Δ among peanut cultivars (Tifton-8, Virginia-81 Bunch, Robut-33-1, Shulamit, McCubbin, Pidie, Rangkasbitung and Cianjur) was conducted using mini-lysimeters (0.8m deep by 0.3m diam.) located within small canopies (8 rows of plants, 6 m long, with an inter-and intra-row spacing of 30 cm) under rain-out shelters (3). WUE of plant growth was measured during 40 to 89 days after planting (DAP). Water used was measured by weighing mini-lysimeters, while total dry matter (TDM) was measured by harvesting and drying plants (including roots) from mini-lysimeters at 40 and 89 DAP. WUE was calculated as TDM/water used over this treatment period. Δ was measured by radio mass spectrometry on ground leaf material.

Results and discussion

The variation in both TDM and water used was not proportional among cultivars, so there were highly significant differences in WUE, with Tifton-8 having the highest (3.71 g/kg) and Rangkasbitung the lowest 2.46 g/kg). Variability in WUE was due to variation in TDM more than that of water use. A strong negative correlation was found between Δ and WUE (P < 0.05, r -0.82), and also between A and TDM (P < 0.05, r - 0.80; Figs la and b).

These results show that differences in WUE and Δ among peanut cultivars, which were demonstrated in individual potted plants (1) also occur for plants grown in small canopies in the field. Measurement of Δ may therefore prove a useful trait for selecting peanut cultivars with improved WUE and TDM under field conditions.

Figure 1.Water Use Efficiency versusΔ[A] , totar dry matter versus A (B).

1. Hubick, K.T., Farquhar, G.D., and Shorter, R. (1986). Aust J. Plant Physiol. 13, 803-16.

2. Hubick, K.T., and Farquhar, G.D., (1989). Proc. 5th Aust. Agron. Conf.Perth.

3. Wright, G.C. and Hatfield, P.M. (1989). Proc 5th Aust. Agron. Conf. Perth.

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