GENETIC IMPROVEMENT OF WHEAT YIELD POTENTIAL AND ADAPTATION IN CHINA - Soybean and Wheat Crops: Growth, Fertilization, and Yield - page 189

C HANGES IN P LANT H EIGHT , H ARVEST I NDEX ,
B IOMASS AND H EADING D ATE

Plant height in Chinese wheat cultivars was significantly reduced (Zhou et al., 2007a and
b). The annual genetic gain in plant height was -0.83% (P < 0.01) in Beijing of Zone I, and -
1.33% (P < 0.01), -0.52% (P < 0.05) and -1.51% (P < 0.01) in Heibei, Shandong and Henan
provinces of Zone II, respectively. The leading cultivars such as Jingdong 8 in Zone I are still
relatively tall (103 cm). The new cultivars, such as CA 9722 and Nongda 3219 with height of
85 cm, are not widely cultivated. All cultivars released after the 1980s in Zone II are 75 to 85
cm tall. Plant height was significantly reduced by the annual genetic gain of -0.76% (P<0.01),
from 122 cm of Mentana to around 90 cm of current cultivars in Zone III. A significant
reduction in plant height (-0.69%, P<0.01) was gained in Zone V. A negative association
between grain yield and plant height was observed in all six trials, i.e, Beijing (-0.76, P <
0.05), Hebei (-0.55, P > 0.05), Shandong (-0.29, P > 0.05), Henan (-0.83, P < 0.01), Jiangsu (-
0.49, P > 0.05) and Sichuan (-0.76, P < 0.01) (Table 5).
Harvest index (HI) increased in all four zones: Zone I (0.92%, P < 0.01, Beijing), Zone II
(0.42%, P < 0.01, Hebei; 0.46%, P < 0.01, Jinan; 0.50%, P < 0.05, Henan), Zone III (0.19, P >
0.05, Jiangsu) and Zone V (0.63, P < 0.01, Sichuan). Significantly positive associations
between grain yield and HI were observed in five trials of Zones I, II and V, ranging from
0.67 to 0.96 (P < 0.05) (Table 5). Slightly positive associations between grain yield and HI
(0.40, P > 0.05) were observed in trial of Zone III. This gave an indication that further
increases in HI may continue to contribute to grain yield improvement.
Only slight changes in biomass were observed in Zones I (0.21%, P > 0.05, Beijing), III
(0.16%, P > 0.05, Jiangsu), V (0.11%, P > 0.05, Sichuan) and some regions of Zone II
(0.05%, P > 0.05, Hebei; -0.01%, P > 0.05, Shandong), but cultivars released from Henan
province was an exception, with the annual genetic gain in biomass of 0.50% (P < 0.01).
Significantly positive correlations between grain yield and biomass were observed in Zones I,
II, III and V, ranging from 0.62 to 0.79 (P < 0.05). This indicates the importance of
improving, or at least maintaining, current biomass in future cultivar development.
Heading date was significantly decreased, with the annual genetic gains of -0.12% (P <
0.01) and -0.22% (P < 0.01) in Beijing and Henan, respectively. Only slight changes in
heading date in Jiangsu (0.03%, P > 0.05), Sichuang (-0.17%, P > 0.05), Hebei (-0.04%, P >
0.05) and Shandong provinces were observed. Significantly negative correlations between
grain yield and heading date were observed in Beijing (Zone I) and Sichuan (Zone V) (Table
5).

Table 5. Correlation coefficients between grain yield (GY) and plant height (PH),
harvest index (HI) and heading date (HD) in autumn-sown wheat cultivars

Location Beijing Hebei Shandong Henan Jiangsu Sichuang

GY-PH -0.76* -0.55 -0.29 -0.83** -0.49 -0.76**

GY-HI 0.94** 0.86** 0.67** 0.76** 0.40 0.96**

GY-HD -0.81** -0.35 0.02 -0.53 -0.42 -0.71**

HI-PH -0.84** -0.88** -0.71** -0.79** -0.59 -0.80**

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