Long-term treatment of low temperature enhanced the polymorphism of Cucumber mosaic virus-BF 2b gene.

CMV-BF infected tobacco(Nicotiana tabacum var.Samsun NN) plants were cultured at two different temperatures(30±5℃ and 10±5℃) for 30 and 80 days,respectively.Viral symptom was observed and 2b gene sequences were analyzed.The results showed that at 30 dpi(days post infection) the hosts exhibi-ted serious viral symptom with many malformed leaves under high temperature(30±5℃),but the plants grown under low temperature(10±5℃) seemed very thin with many white leaves.There were more polymorphisms in CMV-BF 2b gene under high temperature than under low temperature(P0.05).However,at 80 dpi,the viral symptom was somewhat attenuated in the high temperature host group;whereas,much more serious symptom with many malformed leaves and dead plants occurred on the plants grown under low tempe-rature.The number of polymorphisms of CMV-BF 2b gene was statistically higher in the plants under low temperature than of high temperature(P0.05) at 80 dpi.Therefore,low temperature of long-term enhanced the polymorphisms of CMV-BF 2b gene,and it was positively correlated with symptom.