Study On The Inhibition Mechanism And Biocontrol Of Yeast On Anthracnose Of Postharvest Loquat

Loquat（Eriobotrya japonica（Thunb.）Lindl.）,a unique fruit grown in southern China,is well known for its rich nutrition,good taste,and juiciness.However,loquat fruit can be easily infected by pathogenic fungi due to its thin pericarp,leading to serious fruit decay and economic losses.It was confirmed that the main post-harvest disease was anthracnose caused by Colletotrichum gloeosporioides.In this study,a yeast with excellent biocontrol effect was isolated.The efficacy and possible mechanisms of yeast in controlling loquat anthracnose were investigated.Main conclusion of the research are as follows:1.The antagonistic yeast named MA-5 and Lg-3,which can inhibit the growth of C.gloeosporioides,were obtained by in vitro screening.According to physiological and biochemical and molecular biological analysis,the results showed that MA-5 is Saturnispora diversa and Lg-3 is Hanseniaspora thailandica.In vitro experiments verified that the strain MA-5 had a better inhibitory effect on C.gloeosporioides than the strain Lg-3.MA-5 was used in subsequent experiments.2.Through co-culture experiments of yeast and C.gloeosporioides,the optimal ratio of MA-5 yeast suspension to spore suspension was 1×10⁷ cells/m L:1×10⁵spores/m L.The strain MA-5 can be adsorbed on the surface of pathogenic fungus mycelia and spores,and have inhibitory effects on mycelial growth and spore germination.It was also found that the volatile organic compounds produced by S.diversa could not inhibit the growth of C.gloeosporioides.3.The effect of MA-5 on the storage quality of loquat fruit was studied.MA-5treatment can significantly reduce the disease index,browning index and lesion diameter of loquat fruit,and prolong the storage period.At the same time,the reduction of fruit weight and hardness can be delayed,and the content of soluble solids and protein can be increased.4.MA-5 can increase the activity of active oxygen antioxidant enzymes（SOD,CAT,APX）in loquat fruit,and enhance the active oxygen scavenging ability.At the same time,MA-5 can reduce O₂^-.production rate,malondialdehyde content and cell membrane permeability,and prevent cell membrane damage.The treatment of MA-5 has little effect on the content of reduced glutathione（GSH）and ascorbic acid（As A）.MA-5 doesn’t improve biocontrol effect through non-enzymatic system in fruit.5.S.diversa MA-5 induced activities of defense-related enzymes such as polyphenoloxidase,peroxidase and chitinase.6.Analysis of transcriptome data showed that 191 genes were differentially expressed in the fruits of loquat treated with MA-5 strain for 48 h,compared with the control.Among them,154 genes were up-regulated and 37 genes were down-regulated.Combining GO annotation and KEGG pathway,we can find that differentially expressed genes are mainly enriched in biological processes and molecular functions,and affect fruit resistance-related pathways.