Yoshida - 1981 - Fundamentals of Rice Crop Science
Yoshida - 1981 - Fundamentals of Rice Crop Science
Yoshida - 1981 - Fundamentals of Rice Crop Science
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RICE PLANT CHARACTERS IN RELATION TO YIELDING ABlLlTY 217<br />
The plant-type concept has since attracted considerable attention and more<br />
intensive examination in Japan (Murata 1961, Hayashi and Ito 1962, Hayashi<br />
1968, 1969). Experimental data for tropical varieties clearly demonstrate that<br />
certain morphological characters are indeed associated with yielding ability<br />
(Tanaka et al 1964, 1966a). Work on plant type has been well summarized and<br />
the concept appears to have been widely accepted by rice breeders in many<br />
countries as a guide for breeding high yielding varieties (Ishizuka 1971, Jennings<br />
1964, <strong>Yoshida</strong> 1972).<br />
The following morphological characters deserve particular attention:<br />
• Short, stiff culms.<br />
• Erect leaves.<br />
• High tillering.<br />
6.3.2. Short, stiff culms<br />
The increased resistance <strong>of</strong> improved varieties to lodging appears to be the single<br />
character most responsible for high yields. A short, stiff culm makes the rice plant<br />
more lodging resistant. Table 6.2 compares the yield performance <strong>of</strong> Peta, a tall,<br />
lodging-susceptible variety, with that <strong>of</strong> IR8. The mechanical support alone<br />
increased the grain yield <strong>of</strong> Peta by 60% in the wet season and by 88% in the dry.<br />
Although height is the most important plant character associated with lodging, a<br />
short variety is not always lodging resistant. There are differences in the stiffness<br />
<strong>of</strong> short culms (Chandler 1969).<br />
The importance <strong>of</strong> lodging resistance has long been recognized, but only in<br />
recent years has the semidwarf gene been effectively introduced into tropical rice<br />
varieties. In southern Japan, Hoyoku and its sister high yielding varieties are<br />
largely characterized by increased lodging resistance (Shigemura 1966).<br />
6.3.3. Erect leaves<br />
Erect leaves allow the deeper penetration and more even distribution <strong>of</strong> light,<br />
which results in increased crop photosynthesis (see Chapter 5).<br />
In one model, the crop photosynthesis <strong>of</strong> an erect-leaved canopy is about 20%<br />
higher than that <strong>of</strong> the droopy-leaved canopy when the LAI is extremely high (van<br />
Table 6.2. An example <strong>of</strong> the yield performance <strong>of</strong> IR8 and Peta<br />
in the wet and dry seaons. a<br />
Yield (t/ha)<br />
Variety<br />
Wet Dry Mean<br />
season b season c<br />
Peta, not supported 2.83 (100) 3.97 (100) 3.40 (100)<br />
Peta, supported 4.52 (160) 7.46 (188) 5.99 (176)<br />
IR8. not supported 6.10 (216) 9.10 (229) 7.60 (224)<br />
a <strong>Yoshida</strong>, et al (1972). b 1966, 30– x 30-cm, spacing, 100 kg N/ha.<br />
c 1968, 20- x 20-cm spacing, 120 kg N/ha.