International Journal of Agriculture and Food Science Technology. ISSN 2249-3050, Volume 4, Number 6 (2013), pp. 589-594 © Research India Publications http://www.ripublication.com/ ijafst.htm A Study on the Thermo-tolerance at Germination and Seedling Stage in Indian Mustard [Brassica Juncea (L.) Czern & Coss] T.P. Muhammed Azharudheen 1 , D.K. Yadava 1 , Naveen Singh 1 , Sujata Vasudev 1 , Rajendra Singh 2 and K.V. Prabhu 1 1 Division of Genetics, Indian Agricultural Research Institute, 2 National Phytotron Facility, New Delhi, India. Abstract High temperature at germination and seedling stage is becoming a major problem affecting production and productivity of Indian mustard in the major mustard growing states like Rajasthan and Haryana. In an experiment conducted to study whether the thermo-tolerance at germination and seedling stage are correlated in Indian mustard, fifty varieties were screened for their thermo-tolerance at these two stages. A screening protocol which simulates the temperature fluctuations experienced in the field during the germination and seedling stage of the crop was used in the study. Both the experiments were carried out in the controlled growth chamber of the National Phytotron Facility, New Delhi. In the first experiment, the ability of a genotype to germinate under high temperature was assessed in terms of germination per cent. In the second experiment five-days old seedlings were screened under high temperature conditions and seedling thermo- tolerance index was taken as the parameter to assess thermo-tolerance at seedling stage. The correlation between per cent germination under high temperature condition and seedling thermo-tolerance index was not significant. The varieties showing thermo-tolerance at these two stages were also different. This result indicates that thermo-tolerance at germination and seedling stages are not correlated in Indian mustard, and the genotypes tolerant at one stage need not be thermo-tolerant at another stage. So there is a need for separate breeding programmes for thermo-tolerance at these two stages.