EVALUATION AND IDENTIFICATION OF TOBACCO BREEDING LINES FOR WATER STRESS TOLERANCE

Abstract

Tobacco (Nicotiana tabacum L.) is an important industrial crop grown in the states of Andhra Pradesh, Gujarat, Tamil Nadu, Karnataka, West Bengal, Bihar and Uttar Pradesh. The tobacco crop is relatively drought stress tolerant plant but the loss of quality leaf yield in response to water-deficit stress is witnessed in many areas. For selection of drought tolerant genotype the lines need to be screened under artificial condition to ensure that all the genotypes undergo drought stress. In this study artificial water stress has been created for screening the genotypes under in vitro and in vivo condition and the genotypes were selected based on morphological and physiological characteristics. The minimum germination per cent with 1% PEG was found to be 10% and maximum was 90%. Twenty five genotypes showed 90 % germination under stress whereas the susceptible check showed only 10 % germination. In greenhouse, water stress was induced at 35 days after transplantation in pots and the soil moisture (SM) and relative water content (RWC) were recorded three times at weekly intervals. RWC of tolerant lines varied from 40-50 per cent when the soil moisture was below 20%. The height of the genotypes varied from 80 to 100 cm, whereas the height of the susceptible check was 34 cm. A total of 12 genotypes were selected based on the RWC which showed a balanced RWC during three intermittent water stress and the recorded higher photosynthetic rate between 12-18 mmol CO2 m-2s- 1,stomatal conductance 0.2-0.8 H2O m-2 s-1, transpiration rate 6- 9 H2O m-2 s-1 and Ci/Ca ratio 0.6- 0.797.