Effect Of Different Preparation And Treatment Methods On Pineapple Blackheart Control By Endophyte Aspergillus Niger

Pineapple,being beautiful in appearance,unique in flavor and rich in nutrition,and thus popular among consumers,ranks number 1 in international trade of fresh tropic fruits.The sales of fresh fruit pineapple accounted for 70%of the total output in China.However pineapple is susceptible to blackheart during storage and transport,and often leads to serious postharvest losses,which is an important factor restricting the development of pineapple industry.Studying the control method of pineapple blackheart is of great practical importance.The previous research in our laboratory shows for the first time that postharvest application of endophytic Aspergillus niger spore suspension could control blackheart.However,due to the influence of many factors on the activity and mass production of fungal spores,the extension is restricted.In view of this,the effect of different preparation and treatment of A.niger extracts on the control of pineapple blackheart are mainly studied in order to provide new ideas for the development of biological control technology for pineapple blackheart.The main results were as follows:1.Postharvest application of A.niger spore suspension(5×10⁷ cfu?mL^-1)by spraying the crown or fruits of pineapple,respectively,reduced the incidence of pineapple blackheart and kept the crown fresh,whereas the efficacy of either of them was lower than spraying crown plus fruit.This suggests that when A.niger spore is used to control pineapple blackheart,both crown and fruit should be treated to be effective.2.Postharvest application of the liquid medium?diluted by 5 times?to spray pineapple,did not show a good control result on pineapple blackheart.This suggests that there was no ingredient extruded into culture media by A.niger that could control the pineapple blackheart.3.Postharvest application of A.niger hypha extract could reduce the incidence of blackheart and had no effect of abundance of A.niger with in tissues of pineapple,however after spraying spore suspensions to pineapple fruit,there was a significant accumulation of A.niger 5S rRNA in crown,pulp and core.This indicates that hypha extract did not control blackheart by increasing abundance of endophyte A.niger in pineapple fruit.4.Water,sodium hydroxide and ethanol were used as extract solvents,and the optical absorption of the extracts were scanned by UV-Vis spectroscopy for wavelength of peak absorptionin the wavelength range of.The results showed that the peak absorption wavelengths of the three extracts were the same.5.The extract conditions of A.niger hypha for the maximum extract efficiency were:1%of sodium hydroxide,hypha vs liquid ratio of 1:8,and extraction time of 24 h.6.When the extracts of A.niger hypha by 1%sodium hydroxide,70%ethanol and water were applied to pineapple,respectively,by spraying,all reduced the incidence of pineapple blackheart severity,with the extracts by sodium hydroxide being slightly better than the others.