GENETIC IMPROVEMENT OF WHEAT YIELD POTENTIAL AND ADAPTATION IN CHINA - Soybean and Wheat Crops: Growth, Fertilization, and Yield - page 188

In Zone I, cultivars released in Beijing from 1949 to 2000 were characterized by a
significant increase in TKW (1.30%, P<0.01), decreased spikes/m 2 (-0.65%, P < 0.05), and
increased kernels/spike (0.60%, P > 0.05) and kernel weight per spike (1.79%, P < 0.01).
In Zone II, cultivars developed in Hebei province was characterized by a significant
increase in kernels per spike (0.99%, P < 0.01) and kernel weight per spike (1.00%, P < 0.01),
reduction of spike/m 2 (-0.79%, P < 0.05), and a slight increase in TKW (0.06%, P > 0.05).
Cultivars sown in Shandong province was characterized by significantly reduced spikes/m 2 (-
0.74%, P < 0.05), increased kernels per spike (0.54%, P < 0.05) and kernel weight per spike
(0.78%, P < 0.01), and slightly increased TKW (0.35%, P > 0.05). Cultivars planted in Henan
province was only characterized by significantly increased spikes/m 2 (0.59%, P < 0.05),
increased TKW (0.51%, P >0.05) and kernel weight per spike (0.54%, P >0.05), and slightly
decreased kernels per spike (-0.10%, P>0.05).
In Zone III, spikes/m 2 (-0.51%) was reduced, kernels per spike (0.14%), TKW (0.32%),
and kernel weight per spike (0.58%) were slightly increased, but all of them are not
significantly at 5% probability level. In Zone V, it was characterized with a significant
increase of TKW (0.65%, P<0.01) and kernel weight per spike (0.87%, P<0.01). Kernels per
spike (0.20%) was slightly increased, and spikes/m 2 (-0.11%) was slightly reduced, but they
were not significant at P = 0.05.
The simultaneous increase of TKW and kernel per spike observed in Beijing, Hebei,
Shandong, Jiangsu and Sichuan, or the shift of negative relationships between them observed
in Henan, resulted in an increased kernel weight per spike, and thus led to the increased grain
yield. An increase in the number of kernels per spikelet, rather than the numbers of spikelets,
seemed to play a more important role in increasing kernels per spike based on observations in
Shandong. This is further supported by the significant positive correlations between grain
yield and kernel weight per spike ranging from 0.73 to 0.95 (P < 0.05) observed in five trials
excluding Jiangsu (Table 4).
Increased grain yield can also be achieved in different ways in the same location. For
example, Lumai 7 in Shandong province was characterized by average number of spikes/m 2
(553), greater kernels per spike (36.0) and relatively small grain size (40.8g), whereas Jimai
19 had lower number of spikes/m 2 (484), but greater kernels per spike (38.8) and grain size
(45.4g). Lumai 22, called a large spiked wheat cultivar by farmers, is yet another example. It
had less spikes/m 2 (399), but more kernels per spike (45.0) and big kernel size (TKW 47.9 g),
i.e., large and heavy spike, 1.81g, although it is generally believed that a certain number of
spikes is needed for stable yield performance across environments (Zhuang, 2003).
Table 4. Correlation coefficients between grain yield and kernel weight per spike
Province Beijing Hebei Shandong Henan Jiangsu Sichuan

r 0.95** 0.77** 0.73** 0.75* 0.53 0.91**

* and ** indicate significance at p = 0.05 and 0.01, respectively.