| Stem-end rot is one of severe postharvest diseases on Psidium guajava. The disease often occurs on stem, petiole and fruit, starting with circular water-soaked spots on fruits, then with the entire fruit softened, rot and mummified. The colony of the causal fungus on PDA plates is white and gradually turning to gray, with abundant fluffy aerial mycelia. Conidia are initially hyaline and unicellular, subovoid to ellipsoidal with a granular content. Mature conidia are two-celled, cinnamon to light brown in color and often with longitudinal striations and 20～29μm×10～14μm size.According to the morphological characteristics of the pathogen and the 99% identities of rDNA ITS-full gene sequence with that of the genus Botryosphaeria in NCBI, the causal agent was identified as Botryosphaeria rhodina.The B. rhodina grows well on PDA plates at temperatures between 25~30℃, 32℃is the optimum temperature for growth and 25℃is the optimum temperature for sporulation. Sucrose and glucose could promote mycelial growth, sucrose could increase the yield of sporodochium, and the solution of Sucrose, glucose, mannitol and maltose could promote the conidial germination. The mycelial growth and sporulation of B. rhodina were stimulated when cultured under light. B. rhodina could grow at pH values ranging from 4 to 10. However, they grew better under an acidic condition. The conidial germination of B. rhodina needed high relative humidity, the rate of conidial germination increased with the raise of relative humidity, and the germination rate was 88.7 % when the conidiospores of pathogen were incubated in water drop, whereas the conidiospores did not germinate when the relative humidity was below 85 %. The lethal temperature of the mycelium was 52℃for 10min. In vitro experiments showed that Prochloraz, Difenoconazole, Pyraclostrobine, Mancozeb and Chlorothalonil could effectively inhibit the growth of B. rhodina. The EC50 values of Prochloraz, Difenoconazole, Pyraclostrobine, Mancozeb, Azoxystrobinand Chlorothalonil were 0.20786μg/mL, 2.56606μg/mL, 3.76205μg/mL, 4.57956μg/mL, 8.06035μg/mL and10.85537μg/mL, respectively. Prochloraz had the lowest EC50 value and exhibited the highest inhibitory effect on B. rhodina.As there are many fruits imported from Taiwan which have latent pathogens, a rapid and accurate method for the specific detection of B. rhodina is essential to prevent its widespread devastation in mainland of China. Based on differences in internal transcribed spacer (ITS) sequences of B. rhodina and other B. spp., a pair of species-specific primers BF1/BR1 were designed. A single 287 bp band from all isolates of B. rhodina was amplified with this primer pair, but without any amplicants from any other isolates tested. The sensitivity increased by 1000-fold to 1 pg by developing a nested PCR procedure that used ITS1/ITS4 as the first-round primers combined with BF1/BR1 specificity , which could be used to detect B. rhodina in plant tissues infected by the pathogen. The PCR-based detection methods developed here could simplify both plant disease diagnosis procedure and pathogen detection, as well as guide plant disease management.To develop biological control strategy, antagonism of ten bacteria strains against B. rhodina was determined by dual cultural tests. The antimicrobial activities ZB-6 culture filtrate were studied based on mycelium growth rate, cup-plate method and organize method. The stability of culture filtrate in different conditions was measured. The results showed that the culture filtrates had strongly fungistasis effects on germination of B. rhodina spores, and moreover some spores of the pathogen became deformed. The relative inhibiting rates of the culture filtrate in Petri dishes were affected by temperatures and pH values. The relative inhibiting rate was high with pH5.6～8.6 and temperature 40～80℃. The culture filtrate had better protective function to P. guajava and control effcet on B. rhodina.
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