Agriculture Reference
In-Depth Information
and susceptible genotypes exhibited different levels of LIP9,
WCOR413 and DREB1B gene expression. Expression of LIP
was higher in the tolerant genotype after six hours of cold,
whereas WCOR413 expression was highly inhibited by cold in
both genotypes. DREB1B expression increased after six hours
of cold mainly, in the tolerant genotype.
Low temperature is a common production constraint
in rice cultivation in temperate zones and high elevation
environments, with the potential to affect growth and
development from germination to grain fi lling. There is a
wide range of genotype based differences in cold tolerance
among rice varieties, these differences often refl ecting growth
conditions in the place of origin, as well as breeding history.
However, improving low temperature tolerance of varieties has
been diffi cult, due to lack of clarity of the genetic basis to low
temperature tolerance for different growth stages of the rice
plant. Seeds or plants of 17 rice varieties of different origins
were exposed to low temperature during germination (15ºC),
seedling, booting and fl owering stages (18.5ºC) to assess their
cold tolerance at different growth stages. Low temperature
at the germination stage reduced both the percentage and
speed of germination. Varieties from China (B55, Benjiemang
and Lijianghegu) and Hungary (HSC55) were more tolerant
to low temperature than other varieties. Most of the varieties
showed moderate levels of low temperature tolerance during
the seedling stage, the exceptions being some varieties from
Australia (Pelde, YRL 39 and YRM64) and Africa (WAB 160
and WAB38), which were susceptible to low temperature at
the seedling stage. Low temperature at booting and fl owering
stages reduced plant growth and caused a signifi cant decline in
spikelet fertility. Some varieties from China (B55, Benjiemang,
Lijianghegu), Japan (Jyoudeki), the USA (M103 and M104)
and Australia (Quest) were tolerant or moderately tolerant
