Rice Seedling Vigor at Sub‐optimal Temperatures¹

Abstract

A laboratory method was devised for evaluating seedling vigor of rice (Oryza sativa L.) cultivars, hybrids, and segregating populations at sub‐optimal temperatures. Seeds of 20 cultivars of diverse origin were soaked in distilled water for 24 hours at 30 C and then germinated in the dark on moist blotters at 15, 18, 20, 25, and 30 C. Seedling height was used as the primary criterion for evaluation. Growth differences among cultivars, temperatures, and their interaction were highly significant. The same cultivars were evaluated in a field trial where mean days to emergence ranged from 9.4 to 17.7 with a mean of 12.9, and percentage emergence ranged from 22.0 to 87.5 with a mean of 57.4. The above two traits were components of an emergence index which ranged from 12.9 to 76.0 with a mean of 44.4. Correlation coefficients of laboratory seedling heights at five temperatures with days to emergence in the field ranged from ‐0.74 to ‐0.89, at the 1% level, with percentage emergence — from 0.56 to 0.69, at the 5% level, and with emergence index — from 0.75 to 0.81, at the 1% level. Results indicated that performance hi laboratory tests was a satisfactory indicator of field performance.

A Varietal Difference in Coleoptile Growth is Correlated with Seedling Establishment of Direct Seeded Rice in Submerged Field under Low-Temperature Conditions

“…Therefore a low temperature around 16oC is not lethal to rice seedlings, but is low enough to impede the growth of seedlings. Although there is no direct evidence, the slow growth may increase the risk of microorganism hazards in paddy field conditions as suggested by Jones and Peterson (1976).…”

“…On the other hand, many workers have pointed out that there is a wide varietal difference in the seedling establishment at low temperatures (Sasaki and Y amaza ki, 1971;Ikehashi, 1973;Jones and Peterson, 1976;Li and Rutgar, 1980;Kotaka and Abe, 1988;Kowata eta!., 1992;Amana eta!., 1993;Redona and Mackill, 1996;Inoue et al, 1997). The genetic improvement of seedling establishment at low temperatures is considered to be possible by using several varieties superior in seedling establishment as genetic resources.…”

“…Although the relationship between seedling vigor and seedling length at certain days after sowing (Sasaki and Yamazaki, 1971;Ikehashi, 1973;Jones and Peterson, 1976;Li and Rutgar, 1980;Kotaka and Abe, 1988;Kowata et a!., 1992;Amana et a!., 1993;Redona and Mackill, 1996) and the relationship between seedling vigor and germination index (Kotaka and Abe, 1988;Kowata et al, 1992) have been studied, few physiological studies focusing on the above 3 distinctive growth stages under submerged conditions have been reported.…”

“…European and the U.S. varieties were included because of their superior seedling growth (Jones and Peterson 1976;Kotaka and Abe 1988;Kowata et al, 1992;Amano et al, 1993;Redona and Mackill 1996). The seeds of all varieties used in this study (Table 1) were harvested in the experimental paddy fields of the Department of Lowland Farming, Tohoku National Agricultural Experiment Station (Omagari, Akita Prefecture, Japan).…”

α-Amylase Activity and Soluble Sugar Supply from Endosperm in Relation to Varietal Differences in Seedling Establishment under Low-Temperature Conditions in Rice (Oryza sativa L.)

“…In direct-seeded rice (Oryza sativa L.) cultivation, seedling establishment traits show large varietal differences at low temperatures (Sasaki and Yamazaki, 1971;Jones and Peterson, 1976;Li and Rutgar, 1980;Amano et al, 1993;Redona and Mackill, 1996;Inoue et al, 1997;Ogiwara and Terashima, 2001;Ogiwara et al, 2003). Information on physiological characteristics relating to better seedling establishment is essential for post-genome era breeding programs.…”