Preliminary Study On Occurrence Regularity Of Kiwifruit Soft Rot

Kiwifruit has been beloved by consumers because of its unique flavor and high nutritional value.Sichuan is a big province of kiwifruit cultivation.Kiwifruit soft rot(ripe rot)caused by some species of Botryosphaeriaceae was one of the most important diseases in the kiwifruit production,which was widespread and serious harm.At present,the occurrence regularity of the kiwifruit soft rot is not completely clear.The study from dormancy period,the growth period to the fruit harvest,the pathogen-carrying in differtent sites and various parts of the host were surveyed in the whole course,meanwhile the development process of pseudothecium as main primary infenction source was monitored.The purpose of this study was to explore the occurance law and lay the foundation for the prevention and cure of kiwifruit soft rot.From November 2016 to February 2018,the results of study on different sites and various parts of host in dormant period showed that the main overwintering sites of the pathogen were dead branches,followed by fallen leaves and dormant buds.By monitoring the development of pseudothecium,it was found that the pseudothecium began to development in March,asci and ascospores were formed in May,the peak period of releasing ascospores was June to August.By detecting pathogen-carrying at differtent site and various part of host in growth stage,it was showed that pathogen obtained easier under open field cultivation than rain shelter cultivation,and the peak period of pathogen release coincided with the peak period of ascospores release from pseudothecium.By investigation of the incidence of kiwifruit soft rot during storage,and it was found that the percentage of kiwifruit soft rot disease in this period was the highest among all fruit rot diseases,the average ratio was 21.05%,and the incidence was serious.Meanwhile,samples of kiwifruit soft rot were collected in dormant,growth and storage period,and 172 isolates of Botryosphaeriaceae were isolated by tissue separation.Based on morphological characteristics and muli-locus analysis,and verificated by Koch's postulates,all pathogens causing kiwifruit soft rot were identified as 5 species,Botryosphaeria dothidea(84 strains,48.84%),Neofusicoccum parvum(77 strains,44.77%),Lasiodiplodia pseudotheobromae(6 strains,3.49%),L.theobromae(4 strains,2.32%)and N.mangiferae(1 strain,0.58%).Among them,B.dothidea and N.parvum were the dominant species,and N.mangiferae was a rare species.Especially,N.mangiferae and L.pseudotheobromae were the first reported pathogens causing kiwifruit soft rot.