Transgenerational Effect Of Heat Acclimation In The Rice Leaf Folder

The global average temperature is increasing year by year due to human activities.Under the background of climate warming,insects,as small thermotropic animals,are more and more likely to suffer from high temperature stress.The multi-generational heat stress gives the insect population an opportunity of heat selected,and can improve the heat resistance of the insect population to some extent.The rice leaf folder Cnaphalocrocis medinalis is a major rice pests occur in summer,which is affected by the temperature.At present,the influence of high temperature on the development stage of rice leaf folder has been studied,and some studies have explored the molecular mechanism of the thermal adaptation of rice leaf folder from the aspect of heat shock protein.However,the transgenerational effect and genetic characteristics of the heat acclimation effect of rice leaf folder have not been reported yet.In this paper,we take the rice leaf folder reared in indoor wheat as the object,and use the method of short-term high-temperature exercise selection in the larval period to establish a heat selected strain.By measuring and comparing the survival rate of larvae of the heat selected strain and the non selected strain under different high-temperature heat shocks,the spawning amount of the hybrids of the heat selected strain and the non selected strain and the survival of the 3rd instar larvae after hatching,and The heat selected strain of the 3rd instar larvae of different generations after the heat-stopping selected were stopped,in order to ascertain the transgenerational effect and genetic ability of the heat selected effect of the rice leaf folder.The following results were obtained:1.Heat accliamtion of the 3rd-instar larvae of rice leaf folderThe survival rate,pupation rate,eclosion rate,sex ratio and female oviposition amount of each generation of 1-6 generations were measured in the process of three populations of rice leaf folder who were heat selected at 39℃ for 3 hours a day for 4 days.The results showed that the heat tolerance of the 3rd instar larvae of rice leaf folder was improved by successive generations of heat selected.After five generations of heat selected,the heat shock at 39℃ had no effect on them,and the biological characteristics of each instar larvae had no significant difference from the control without heat selected.The 3rd instar larvae of rice leaf folder have obvious adaptability to high temperature2.Effect of heat accliamtion on the heat tolerance of rice leaf folder larvaeThe survival of the 1st-5th instar larvae of each strain under the heat stress at 36℃ and 41℃ was studied by using 39℃ heat selected strain,41℃ heat selected strain which had been trained at high temperature for many generations and 27℃ non selected strain as experimental materials,The results showed that after several generations of heat selected,the adaptability of each instar larvae to other high temperature was significantly improved.3.Phenotypic inheritance and transgenerational effect of heat adaptation in rice leaf folderThe 3rd larvae with multi-generation heat selected were used as heat selected strain.To figure out the transgenerational effect and genetic ability of larvae of the rice leaf folder,we measured fertility and offspring survival rate in the 3rd instar under heat stress of hybridization by heat selected strain and non selected strain,the 3rd larvae survival rate of the offspring from heat selected strain which stop heat stress for different generations.The result show that after thirty-generation heat stress,heat adaptation ability of hybridization offspring was between the two parents and could be hereditary.The survival rate of the 3rd instar larvae of the heat selected inbred progeny is high under high temperature,and the survival rate of the hybrid progeny of the heat selected strain and non heat selected strain progeny is in the middle,but the survival rate of the non heat selected strain inbred progeny is the lowest,which shows that the heat resistance obtained by the heat acclimation in the larval stage of the rice leaf folder has certain heredity,The number of eggs laid by a single female was not significantly different between the two strains which indicated there were no reproductive cost in heat resistance of heat selected strain.The heat tolerance of the 3rd instar larvae from the three 39℃ heat selected populations after 6 generations of heat selection was still significantly higher than that of the non selected strain in some recovery generations,indicating that there was a certain generational effect on the heat tolerance of the rice leaf folder.