RESUMO
An experiment was conducted to evaluate the cold tolerance ability of ten boro rice genotypes in the laboratory conditions for suitability of growing under low temperature stress. The experiment was laid out in Factorial CRD and the low temperature regimes was provided under controlled environment (Walk-in cold chamber by Saveer Biotech Limited) for germination studies that could maintain the specific low temperature. The experiment was conducted in the Department of Crop Physiology and Agricultural Biotechnology, Assam Agricultural University, Jorhat, Assam, India. The germination tests were conducted under four different temperature regimes where seed germination under ambient (T4=28 ± 0.2oC) was considered as control. Low-temperature treatments were provided by the growth chamber at three different levels of low temperature viz. (T3=10-12°C), (T2=7-9oC) and (T1=5-6°C). Per cent germination, germination index, shoot length, length of longest root and seed vigour index were considered for the study. The germination percent, germination index, shoot length, length of longest root and seed vigour index was recorded highest under ambient condition (T4) irrespective of all the genotypes. Seeds grown under T3 showed considerable germination values only after 28 days of germination studies, whereas T1 and T2 showed no germination. The study revealed that amongst all the ten genotypes, Kanaklata and Sona Mahsuri revealed superior performance in germination percentage, germination index, shoot length, length of the longest root and seed vigour index. In the correlation studies, germination % was significantly correlated with germination index, shoot length, length of the longest and SVI at 5% probability level. GI was also positively and significantly correlated with Shoot length (SL), Length of longest root (LLR) and Seed Vigour Index (SVI). The present study revealed that Sona Mahsuri and Kanaklata was found to be the ideal genotypes for germination under low temperature (10-12oC). Therefore, Farmers growing boro rice under low temperature regimes could take the opportunity of selecting the varieties viz. Kanaklata and Sona Mahsuri for higher yield.