Abstract: Two high-active strains of INA bacteria, IHM4(Erwinia herbicola) and ISSO1 (Pseuolomonas syringae), were tested for the role in frost injury to maize and soybean under both laboratorial simulation and natural conditions. Results demonstrated that the presence of INA bacteria was one of key factor in inducing frost damage to the two crops. The seedlings of 3-4 leaves treated by spraying with INA bacterial suspensions containing 5×10~3 cells per ml suffered frost injury at -2.5℃ to-3.0℃, whereas the untreated seedlings started to be obviously frozen at -6.0℃ to -7℃. The severity of frost injury increased with lower leaf temperature and higher concentration of INA bacterial populations. A linear relationship was found between the severity of frost injury (I) , leaf temperature (T) and logarithum of INA bacterial population (P):maize I=-92.4684-23.5655T+8.1622 logp soybean I=-96.80-27.28T+7.18 logp

Key words: NULL, NULL