Many studies have recently demonstrated that exogenous spray double-strand RNA（ds RNA）,also known as spray-induced gene silencing,is a unique technique for gene silencing.However,due to the poor stability of RNA and low plant absorption rate,the induction efficiency of RNAi by direct spraying of the ds RNA is low,and the action time of RNAi is short.In order to improve the stability of RNA and the efficiency of host absorption.In our study,si RNA targeting the Bc-DCL gene of Botrytis cinerea was designed;the stem-loop sequences for each antifungal s RNAs identified in previous research in our lab using homemade software were connected in series to form a long single-strand RNA,namely RNApen,suitable for in vivo synthesis by E.coli.Moreover,the production efficiency and anti-fungal activities of both ds RNA and RNApen were analyzed.The template DNAs encoded ds RNA and RNApen were inserted into an E.coli expression vector and induced by IPTG.The results showed that only RNApen was induced and showed a specific band.To investigate the stability of the RNApen,storage of the RNA at room temperature and 37°C at three different time points and checked by gel-electrophoresis,the results showed that as time increases,RNA will continue to degrade.By the 7th day,the 37°C RNA group could not be detected by gel-electrophoresis,but at the same time,room temperature did not completely degrade.However,Both RNA is stable at least after three days at room temperature and 37°C.To investigate both RNAs’inhibition effectiveness on Botrytis cinerea spore germination,we conducted this experiment in PD（potato dextrose）liquid medium,200 ng/?l RNA,and fresh spores were used.These findings demonstrate that ds RNA and RNApen drugs efficiently prevent Botrytis conidia germination.These findings also suggest that RNApen inhibits conidia germination more than ds RNA drugs.To investigate the inhibition efficiency of both RNAs to mycelium growth on PDA,we added RNA drugs to the PDA medium and added small pieces of2days old newborn mycelium;the results showed a significant difference in growth from the control group.This result indicates that two RNA groups significantly affect the virulence of Botrytis cinerea mycelium growth in a solid PDA medium.To investigate the effect of both RNAs on plants against Botrytis,We direct spray 200 ng/μl of both RNAs on the surface of leaves of tobacco,tomato and Arabidopsis,then infected leaves by spore and newborn mycelium.The results showed that both RNAs have an obvious inhibition of gray mold,but RNApen had the lowest disease spot on the leaves.To detect the environmental toxicity of both RNAs,we conducted a toxicity test on the tadpole and small fish spp.The results demonstrated that both RNAs were not hazardous to both species.Our findings add to the growing body of data supporting the use of spray-induced gene silencing of pathogenicity gray mold and host absorption of exogenous RNAs.