PURPOSE: To efficiently prepare the subject plant by culturing the callus of a dedifferentiated paddy rice in a specific medium, screening the grown tenuazonic acid-resistant callus and subsequently redifferentiating a paddy rice young seedling from the resistant callus.

CONSTITUTION: The calluses of a paddy rice redifferentiated from a perfectly ripe seed such as the seed of KOSHIHIKARI (a king of the paddy rice) are prepared and the medium (e.g. R2 medium) employed for the culturing of the calluses is mixed with tenuazonic acid in a concentration of 5-200ppm (preferably 50-100ppm), the tenuazonic acid preferably being isolated and purified from the culture solution of blast microbes and being dissolved in a small amount of dimethyl sulfoxide. The calluses are cultured at 25-28°C under a condition of 2000-3000lux (for 18 hours) in the medium, and the grown tenuazonic acid- resistant strain survived in the medium is cultured in a redifferentiation medium (e.g. a morpholine-free R2 medium) to prepare a transplantable plant. The plant is transplanted, grown for 2-3 weeks and subsequently sprayed with the suspension of the spores of the blast fungi to judge the extent of the symptom of the blast, thus providing the objective plant.