Infection Characteristics Of Pathogens Ssociated With Moldy Core Of Fuji Apple

Moldy core is an important disease of apple. It is characterized by the growth of themycelia within the core, or appearance of the rot in the fleshy tissue surrounding the core. Theinfected fruits have poor quality and may drop prematurely. So this disease takes the seriouseconomic loss in production and storage of apple. Moldy core is caused by a variety of fungi.In this paper, the infection characteristics of pathogens, and the composition of pathogens indifferent orchards were studied. The main results were as follows:(1) The pathogens were isolated from Fuji apple in different development stagesassociated with moldy core, and we found that each species had different infection periods.Alternaria alternata occurred in dormant period (November) of90%isolation rate, about60%before fall of last petals, and13%40%in young fruit. A. arborescens and A. tenuissima,which were10%and20%from dormant to petal fall, respectively. These two speciesoccurred below10%in young fruit. Cladosporium cladosporioides and C. tenuissimumoccurred in dormant (February to March); the isolation rates were33.3%and23.3%in fall oflast fall,80.0%and36.7%in young fruit (after20days of petal fall), respectively. Epicoccumnigrum has20.0%of isolation rate in dormant (November);2040%before apparent swelling;below10%in the sepals let the petal appear. Phoma glomerata was firstly occurred in thedormant of March with16.7%isolation rate;2040%before floral bud appearance; below10%in the sepals let the petal appear. Trichothecium roseum was firstly occurred in youngfruit of June (after40days of petal fall) with3.3%isolation rate; and reached to43.3%onemonth later (after70days of petal fall). Fusarium tricinctum, Penicillium chrysogenum, P.commune, P. expansum and P. purpurogonum were only occurred in several periods, and theisolation rates below10%.According to the above results, we can speculate that A. alternata, A. arborescens, A.tenuissima, E. nigrum and Ph. glomerata can infected flower bud in dormant. C.cladosporioides and C. tenuissimum can also infected flower bud, but mainly infected fruitthrough calyx tube after petal fall. However, T. roseum infected fruit only through calyx tube. Therefore, we considered that fungicide should be sprayed at dormant, after fall of last petal,before fruit bagging to control moldy core.(2) We found the two symptoms, browning and moldy core, which were related todifferent species, inoculum concentration and combined infection.For A. alternata and A. tenuissima, browning occurred following inoculation with1×105spores/mL, whereas moldy core occurred with1×106spores/mL. For A. arborescens,browning occurred with1×1056spores/mL, moldy core with1×107spores/mL. For C.cladosporioides, browning occurred with1×106spores/mL, moldy core with1×107spores/mL. For C. tenuissimum, browning occurred with1×1067spores/mL, moldy corewith1×108spores/mL.For A. alternata, A. arborescens and A. tenuissima, browning occurred following everytwo species combined inoculation with1×105spores/mL; C. cladosporioides and C.tenuissimum caused browning by combined inoculation with1×105spores/mL. For A.arborescens, C. cladosporioides and C. tenuissimum, moldy core occurred following everytwo species combined inoculation with1×106spores/mL.Results from this study suggest that inoculation concentration from1×104spores/mL to1×108spores/mL should be used in pathogenicity tests of moldy core.(3) Pathogens were obtained in fruit samples from Yangling and Baishui. We found thatisolation rates of A. alternata occurred with13.3%and16.0%in Yangling and Baishui,respectively. A. arborescens was1.3%and2.7%, respectively. A. tenuissima was2.0%and3.3%, respectively. C. cladosporioides occurred with12.7%and5.3%, respectively. C.tenuissimum was0.7%and2.7%, respectively. E. nigrum occurred with20.0%and14.0%,respectively. Ph. glomerata occurred with2.7%and6.0%, respectively. T. roseum occurredwith8.0%and3.3%, respectively. Consequently, pathogens associated with moldy core werealmost the same, just different in the isolation rate.(4) Two new records of Cladosporium from China were found in this study, C.asperulatum and C. bruhnei, respectively. In pathogenicity tests, these two species causedmoldy core.