インド型短稈改良稲の温帯における収量性

To analyze the relation between yields and yield components of indica，japonica and intermediate types of rice in the temperate zone，an analytical survey on the varietal difference of paddy yields was carried out in the Tropical Agriculture Research Center in Tsukuba Science City situated 60 km from Tokyo. Ten varieties，consisting of 6 semi-dwarf improved varieties of indica rice-Taichung Native 1，IR 2061，IR 36，C 4-63，IR 24 and Suweon 258，2 intermediate types of rice-Arborio J 1 and British Honduras and 2 japonica types of rice-Nihonbare and Reiho，were transplanted with the randomized block method of 4 replications on 21st May 1981. 1. The paddy yield was the highest for Suweon 258 (80 kg/a)，and it showed a decrease in the following order :IR 24(72kg/a)≒IR206I(69kg/a)>C4-63(65kg/a)≒IR36(63kg/a)≒Taichung N.1(61kg/a)≒Nihonbare(60kg/a)>Reiho(55kg/a)>B. Honduras(49kg/a)>Arborio J 1(36kg/a). In other words，the yield of semi-dwarf improved varieties of indica rice was higher than those of japonica intermediate types of rice. 2. The number of panicles/㎡ was superior in IR 36，Suweon 258，Taichung N.1 as compared with those of C 4-63，B. Honduras and Arborio J 1，which were tall varieties. The number of spikelets/㎡ was also superior in Suweon 258，C 4-63，IR 2061 and IR 36，which were influenced either by an increase of the number of panicles/㎡ or an increase of the number of spikelets/panicle，a s compared with 2 intermediate and 2 japonica varieties. The percentage of ripened grains of these semi-dwarf improved indica types of rice was 54-66%，while that of the 2 japonica types of rice was 81%. 3. Although positive correlations between paddy yields，and total weight of plant, number of spikelets/panicle，grain/straw ratio，number of panicles/㎡ and numberof spikelets/㎡，as well as negative correlations between paddy yields，culm height and the weight of 1,000 grains，were found respectively，the number of spikelets/㎡ showed the highest correlation coefficient，r＝0.860***　with paddy yields. The number of spikelets/㎡ closely correlated with the number of panicles/㎡ and also the number of spikelets/panicle. However，correlation between paddy yields and percentage of ripened grains is not consistant，because there is a negative correlation between percentage of ripened grains and number of spikelets/panicle. Thus it was made clear that number of spikelets/㎡ is the main factor contributing to paddy yields.