Located mainly in the dryland areas, the Loess Plateau is an important region for crop production with winter wheat (Triticum aestivum L.) as a major crop all over the lands. In cropping systems, winter wheat cultivars play an important role. For obtaining high and stable wheat yields in the region, it is of significance to select the most suitable variety of winter wheat for practical use and reveal the differences of dry matter accumulation and translocation of the winter wheat cultivars with various-yielding levels for understanding of their internal characteristics. For this purpose, a field experiment was conducted from 2008 to 2009 in a site where no fertilizer had been received for six years before the trial. Two factors were included in the experiment: wheat cultivars and fertilization. Nine wheat cultivars with different yield levels released and widely adopted in the region were utilized as testing materials and each was planted at three nitrogen and phosphate input rates with four replications. During plant growth period, plants were sampled at flowing and harvest stages and the total dry matter amounts and the dry matter accumulation pre- and post-anthesis were measured so that the differences of dry matter translocation, dry matter transported amount and rate, transferred efficiency as well as the contribution of the transferred dry matter to grains could be evaluated for those winter wheat cultivars. In addition, the leaf area, SPAD value and photosynthetic rate were also determined at some stages for further illustrating the yield-forming traits. The leaf area was measured at booting stage by LI-3000A leaf area instrument, the SPAD at both booting and grain filling stages by SPAD device, and photosynthetic rate at grain filling stage by LI-6400 portable photosynthetic instrument. The results showed that dry matter, dry matter accumulation during pre-anthesis and post-anthesis, dry matter transferred efficiency and the contribution of transported dry matter to grain yield were significantly different for different winter wheat cultivars. Compared to the control without fertilization, the total accumulation productions of the high, middle and low yielding cultivars were 29%, 22% and 6% increased for the low fertilizer input treatment, and 46%, 39% and 23% for the high fertilizer input treatment, respectively. With the increase of fertilizer rate, the dry matter accumulation in the post-anthesis was increased for the different yielding cultivars whereas, the dry matter translocation, transferred efficiency and the contribution of the transferred dry matter to grain yield were decreased. At the grain filling stage, the SPAD value of their functional leaves or flag leaves of high, middle and low yielding cultivars was 20.7, 17.5 and 13.7 for the low fertilizer input treatment, while 35, 26.1 and 16.8 for the high fertilizer input treatment, respectively. The photosynthetic rate of high yielding cultivars (Xinong 88) was 6.0 μmolCO₂·m^-2·s^-1 whereas the average photosynthetic rates of middle and low yielding cultivars were 4.3 and 4.0 μmolCO₂·m^-2·s^-1, respectively. The high-yielding variety was characterized with high levels of total dry matter production and also with high dry matter accumulation after anthesis. The high dry matter increase after anthesis might be related with the high SPAD value and high photosynthetic rate of the functional leaves during the grain filling stage.
In summary, the higher level of SPAD value, photosynthetic rate and dry matter accumulation after anthesis was one important reason for wheat cultivars with high grain yields on drylands of the Loess Plateau. Therefore, selecting qualified wheat cultivars, adopting adequate cropping measures as general, and especially maintaining a high dry matter accumulation during post-anthesis through the regulation of nutrient management could be regarded as the essential ways for further improvement of winter wheat yield production in the area.