the first symptom of soft rot on apple fruit was a water - soaked appearance to the affected tissue .
the diseased parts later disintegrated into a mushy mass of disorganized cells that sloughed off .
white mycelia formed on infection sites of apples and gradually covered the fruit with tufted whisker - like gray sporangiophores and sporangia ( fig .
sporangiospores , sporangia , and sporangiophores were observed under a light microscope ( table 1 ) .
the fungal colonies that grew on potato dextrose agar were initially white and cottony , then became heavily speckled with sporangia , and finally became brownish - grey to blackish - grey and spread rapidly with stolons fired at various points to the substrate by rhizoids ( fig .
the optimum temperature for mycelial growth was 30 , with good growth still apparent at 37. sporangiospores were unequal , numerous , irregular , sub - globose or oval , angular with striations , and 4~8 m ( fig .
smooth - walled , simple or branched , non - septate , long , and arose from stolons opposite rhizoids usually in groups of 3~5 or more .
sporangia were globose , white at first , and then turned black with many spores , mostly 40~200 m ( fig . 2c ) .
columella were globose to sub - globose , pale brown , and mostly 85~110 m ( fig .
twelve apple fruits were artificially inoculated with a representative fungus using the wound infection method . a conidial suspension ( 0.1 ml ;
3  10 conidia / ml ) of the causal fungus was placed on the surface of apple fruit .
the inoculated fruit was kept in a moist chamber with 100% relative humidity at 30. after a 3 day incubation , the same fungal symptoms were reproduced : soft rot was observed on inoculated fruits that was identical to symptoms observed at the commercial markets ( fig . 1c and 1d ) .
to confirm the identity of the causal fungus , the its rdna of the isolate was amplified and sequenced using its1 ( 5'-tccgtaggtgaacctgcgg-3 ' ) and its4 primers ( 5'-tcctccgcttattgatatgc-3 ' ) , as described by white et al . .
a phylogenetic analysis was performed using mega4 with the neighbor - joining method and the tajima - nei distance model .
previously published its sequences from r. oryzae strains were included for reference , and mucor miehei ( genbank accession no .
the present isolate was placed within a clade comprising r. oryzae references isolates ( fig .
soft rot of apple caused by r. stolonifer has been reported previously , but soft rot caused by r. oryzae has not been recorded in korea .
the representative culture of the causal fungus was deposited in the korean agricultural culture collection ( kacc 45815 ) , national academy of agricultural science , suwon , korea .
based on the mycological characters , molecular data , and pathogenicity testing of the host plant , the fungus was identified as rhizopus oryzae went & prisen geerligs .
 soft rot in apple caused by rhizopus oryzae was found for the first time in korea . 
 a detailed description of the specimen is given along with its internal transcribed spacer rdna sequence . 
 the fungus was identified as rhizopus oryzae based on the mycological characteristics , molecular data , and pathogenicity testing . 
Symptoms
Mycological characteristics
Pathogenicity testing
Internal transcribed spacer (ITS) sequence analysis