Effect Of Cryptococcus Laurentii On Inducing Disease Resistance In Cherry Tomato Fruit And The Possible Defense Mechanisms Involved

Biocontrol is a promising method believed to replace chemical fungicide in the future.Apart from competing for nutrition and space with pathogen,antagonists like yeasts can induce plant disease resistance,which is an ideal mode of action in controlling postharvest fungal decay on fruits and vegetables.However,little is known about the mechanism of this effect.In this study,resistance of cherry tomato fruits in different maturity periods induced by Cryptococcus laurentii was studied,as well as the change of fruit quality.What's more,this study comprehensively revealed the possible mechanism of induced resistance by measuring the expression of genes involved in several plant defense related signaling pathways.Following are the main results:1.When treated with certain cell density of C.laurentii for certain time,the resistance of mature and semi-mature cherry tomato fruits against Botrytis cinerea and Alternaria alternate was highly induced as the disease incidences significantly decreased.This may be attributed to the highly increased activities of SOD,CAT,POD,PAL and GLU.2.Results of RT-qPCR showed that the expression of several genes involved in salicylic acid(SA)and jasmonic acid signaling pathways were activated in succession(genes involved in JA signaling pathway were first inhibited),while genes involved in Brassinosteroids(BRs)signaling pathway were activated and those in Abscisic acid(ABA)signaling pathway were first activated then inhibited,indicating that induced resistance in cherry tomato fruits by C.laurentii may be achieved by regulating several important phytohormone signaling pathways.3.Genes involved in Pathogen-Associated Molecular Pattern(PAMP)-Triggered Immunity(PTI)signaling pathway like BAK1,Bti9,MEKK1 and WRKY33 were found to be significantly up-regulated.Additionally,genes encoding pathogenesis-related proteins and some antioxidant enzymes were also highly up-regulated.All these facts indicate that C laurentii can activate PTI signaling pathway in cherry tomato fruit.4.Physicochemical parameters like fruit weight,firmness,chroma,total soluble solids,titratable acid and ascorbic acid content of were measured.Results indicated that C.laurentii has positive effect on maintaining fruit quality of cherry tomato as the values of fruit weight,ascorbic acid content and chroma were significantly higher after treated with C.laurentii.