Koleckera apiculata strain 34-9 preparation for biocontrol of postharvest decay of citrus and possible mode of action
Long CA, Yuan G and Deng BX
Program and Abstracts, 11th International Citrus Congress (ISC Congress), 26-20 October 2008, Wuhan, China. 333 pages.
2008
บทคัดย่อ
Koleckera apiculata strain 34-9 preparation for biocontrol of postharvest decay of citrus and possible mode of actionCitrus unshiu “Gouqing 1”was used as material for elucidating the effect of Kloeckera apiculatastrain 34-9 suspension postharvest treatment on preventing fruit decay during storage period. The result showed that K. apiculata strain 34-9 preparation of 2×106 CFU/ml (CFU, cloning forming unit) significantly reduced the natural development of decay following storage at 5°C for 100 d, and the application of isolate 34-9 resulted in low average decay incidence in citrus fruit 0.77%, compared with 11.43% in the untreated control citrus fruit. The yeast antagonist had no significant effect on firmness, total soluble solids, ascorbic acid or titratable acidity after three month storage at 5°C. The populations of K. apiculata strain 34-9 on the surface of the citrus fruits varied remarkably with different treatments. At the beginning of the experiment (time 0 h), the yeast population was 2×106 CFU/ml. per citrus fruit with yeast cell suspension treatment, and increased to 1.7×107 CFU/ml in citrus during the period of 0-40 d storage, then stabilized thereafter (3.5×105CFU/ml to 7×105 CFU/ml per citrus). In addition, the yeast population of both carbendazim treatment and control was less than that of yeast cell suspension treatment during storage. During storage, the change of relative electrical conductivity (REC) showed a coordinate tendency with malondlaldehyde (MDA) content, which kept continuously growing from the beginning to the end of the storage. In the storage period of 25 d, the REC value and MDA content of the treatments were all significantly lower than those of water treatment, but had no obvious difference from those of carbendazim treatment. K. apiculata strain 34-9 had no effect on the enzyme activity of super oxide dismutase (SOD), but significantly improved peroxidase (POD) activity after 100 d storage. After storage at 5°C for 100 d, K. apiculatastrain 34-9 did not alter any quality parameters of citrus fruit. Observation under light microscopy and scanning electron microscopy revealed attachment of K. apiculata strain 34-9 to the P. italicum hyphae. We suggest that the high antagonistic activity of K. apiculatastrain 34-9 against citrus blue mold may be related to its capability to compete with P. italicum, for space and nutrients and /or involvement of directly antagonist of the yeast on the fungus.