J.I. Ortiz-Monasterio R., R.J. Peña, and W.H. Pfeiffer

Introduction

Close to 95% of durum wheat cultivars released in developing countries are derived from CIMMYT germplasm. Insufficient water and low nitrogen levels are the two main abiotic stresses present in durum wheat production systems around the world. The objective of the study reported here was to evaluate grain yield and grain quality of durum wheat landraces and CIMMYT durum wheat genotypes under water and nitrogen stress.

Materials and Methods 

A field experiment was established at CIMMYT's research station in Cd. Obregon, Sonora, Mexico, during the 1998-99 crop cycle. A  two-factorial treatment design was used. Factor A consisted of four environments: 1)water stress and nitrogen stress, 2) water stress and no nitrogen stress, 3) no water stress and nitrogen stress, 4) no water stress and no nitrogen stress. Factor B had eight genotypes: one landrace (selected for good performance under low N), two released cultivars, and five advanced lines. The experiment was design as a randomized complete block design with eight treatments (genotypes) and three replications across the four environments. The four environments were within meters of each other.

Pasta-making quality was determined by measuring protein quantity (NIR analysis), protein quality (as indicated by SDS sedimentation, Mixograph dough mixing time, and mixogram peak height), and flour yellowness (Minolta, b). Grain yield was measured in an area of 3.6 m² and expressed at 12% moisture.

1) water and nitrogen stress		2) water stress and no nitrogen stress
3) no water stress and nitrogen stress		4) no water stress and no nitrogen stress

Results

Grain yield

Averaged over all eight genotypes, the effect of nitrogen stress alone reduced grain yield by 57%, water stress alone by 65%, and water and nitrogen stress together by 71% with respect to the non-stressed plots (grain yield: 7,088 kg/ha) (Figure 1). In all four environments, the landrace was outyielded by released cultivars Altar 84 and Rascon 43 and/or by new advanced lines. In the non-stressed environment, two advanced lines (Kucuk and Sooty/Rascon) outyielded the released cultivars (Table 1). Under nitrogen or water stress there was no difference between the released cultivars and the new advanced lines. However, when nitrogen and water stress were present together, the advanced line Sooty/Rascon and cultivar Rascon 43 had 38 and 23% higher yield, respectively, than Altar 84 (Table 1).

Grain quality

There were significant differences among cultivars for most quality parameters within each of the four environments. Rascon 43 was recently released under the name Nacori 97 in the Yaqui Valley of Mexico for its good quality. Sooty/Rascon had better quality based on sedimentation values than released cultivars in all four environments. The environment had a significant effect on flour protein. The highest protein concentration was obtained under + water stress and - nitrogen stress, while the lowest was obtained with the - water stress and + nitrogen stress treatment (Figure 1). The two environments with nitrogen stress were better for discriminating low vs. high protein cultivars; the best one had nitrogen and water stresses present together. Across environments there has been continuous progress in N use efficiency as measured by protein yield (Table 2). Under water stress, nitrogen application did not show an effect on gluten strength parameters (Figure 2). Just the opposite occurred under the no water stress conditions. In general the yellow color of the endosperm increased with the application of nitrogen (Figure 3).

Fig. 2. SDS sedimentation and mixograph values under four environments averaged across eight genotypes.

Fig. 3. Grain color under four environments averaged across eight genotypes.

Conclusion

• Under nitrogen and/or water stress, at a yield level of 2 t/ha and above, the released CIMMYT cultivars and/or advanced lines showed higher yield, better protein quality, and more yellow pigment content than the landrace evaluated.
• Among the genotypes tested, there was more genetic diversity for protein quality than protein quantity.
• A new advanced line, Sooty/Rascon, showed better performance under water and nitrogen stress than the released cultivars.
• In the absence of water stress, nitrogen fertilization is necessary for quality attributes to be expressed, particularly gluten quality. In contrast, under water stress and low yielding conditions, nitrogen fertilization is not as important to realize the gluten quality of the crop.

© CIMMYT July 2001

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