GENE EXPRESSION STUDIES FOR LOW TEMPERATURE TOLERANCE AT THE BOOTING STAGE IN RICE
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Date
2023
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Abstract
Rice (Oryza sativa L.) is a staple food crop for half of the world’s population and it has been
grown as major cereal crop in three distinct seasons in Assam. Out of various constrains of rice
production, abiotic stresses such as drought, low temperature (LT), salinity adversely affect
crop growth and development. Low temperature stress at the early growth and reproductive
stages in rice are critical, and the present study was conducted to screen low temperature
tolerant genotypes at the booting stage (intermediate stage of reproductive phase) and study
gene expression for cold responsive genes in tolerant and susceptible rice genotypes. A total of
30 rice cultivars collected from Regional Agricultural Research Station, Karimganj, AAU were
subjected to low temperature stress at the booting stage in a growth chamber maintained at 12-
12.5C for seven days. The recovery and low temperature tolerance of plants after stress were
evaluated based on pollen fertility, number of panicle emerged, number of seeds set and grain
yield. The results revealed that the phenotypes of C-59 and IET-9097 were superior for all the
traits under study whereas Costco and IET-8687 showed lowest trait values, indicating varied
levels of low temperature tolerance at the booting stage. These four cultivars, C-59 and IET-
9097 as low temperature tolerant; Costco and IET-8687 as low temperature susceptible were
chosen to study gene expression analysis using six cold responsive genes (OsCOLD1,
OsDREB2A, OsCTB1, OsLTT1, OsAPX1, OsNAC9) through real time quantitative reverse
transcriptase polymerase chain reaction (RT-qPCR). The results showed that all the genes were
up-regulated in the cold tolerant cultivars, C-59 and IET-9097 and down regulation in the other
two cold susceptible cultivars, Costco and IET-8687. After performing qRT-PCR analysis,
correlation between the gene expression data and phenotypic observations followed by path
analysis was performed to detect associations between the genes and phenotypes. Path analysis
revealed that out of six genes used in the study, three genes showed direct positive effect over
grain yield (OsDREB2A, OsCTB1 and OsNAC9) and three genes showed indirect effect for
grain yield (OsCOLD1, OsLTT1 and OsAPX1). The study is preliminary with respect to low
temperature tolerance at the booting stage using rice collection of AAU and hence, further
validation is required.