Studies On Identification And Control Of The Pathogens Causing Two New Diseases On Soft-seeded Pomegranate In Xichuan County

Pomegranate is an excellent deciduous fruit tree with multiple functions.In recent years,two new fungal diseases(pulp rot and Alternaria leaf spot)occurred on soft-seeded pomegranate in Xichuan county,Nanyang city,Henan Province,resulting in a serious decline in the yield and quality of pomegranate.In order to identify the pathogens causing the diseases and search for effective control measures,the author isolated and purified the pathogens,confirmed the pathogenicity of representative strains according to Koch’s postulates,studied some biological characteristics of the pathogens.The pathogens were identified based on their morphological characteristics and the sequences of ribosome gene internal transcribed spacer(r DNA-ITS).The methods of biological control and chemical control against pulp rot of pomegranate were preliminarily studied and discussed.The main results were summarized as follows:1.According to the morphological characteristics and pathogenicity of pathogens,combined with r DNA-ITS sequence analyses,the pathogen causing pomegranate pulp rot was identified as Talaromyces albobiverticillius with 26-28℃ as its optimum growth temperature,and two peaks(p H 5.5 and p H7-10.5)of growth p H in PDB.The pathogen causing pomegranate Alternaria leaf spot was identified as Alternaria alternata.2.A total of 120 strains of endophytic bacteria were isolated from healthy soft-seeded pomegranate plants,of which 15 had antagonistic activity against T.albobiverticillius.The isolation rate of endophytic bacteria was 12.5%.Of the endophytic bacterial strains isolated,the two strains B6 and C8 had the strongest efficacy in suppressing the growth of T.albobiverticillius.Strain B6 was identified as Curtobacterium pusillum and strain C8 as Bacillus cereus based on their morphological characteristics,physiological and biochemical tests,16S r DNA sequence homology and phylogenetic tree analysis.3.A field trial in 2021 showed that the control efficacy of a fungicide combination[33.8ml(a.i.)/hm~2plus 360 g(a.i.)/hm~2mancozeb]was the highest(72.02%)among six fungicide combinations tested in suppressing the occurrence of pomegranate pulp rot.