| According the statistics of Fujian edible fungi office, Agaricus blazei production reached 25 to 36.8 thousand tons from 2003 to 2007 in Fujian Province. In recent years, A. blaze industry develops rapidly and shows a excellent market prospects along the development of breeding and cultivation technology. But A. blazei highly enriches cadmium in the cultivation process, and affects food safety, which prevents from its development. Therefore, it is important investigate the impact of cadmium on physiology and biochemistry of A. blazei and study on A. blazei tolerance to cadmium and response mechanisms.In this study, the two varieties of A. blazei (J77 and J85))provided by Fujian Academy of Agricultural Sciences were used to study the their difference in cadmium enrichment and the effects of different cadmium stress on physiology and biochemistry of them. The main conclusions are as follows:1. The mean mycelium growth rate of two A. blazei showed a trend of up-down-rise-drop with the increase of exogenous cadmium addition. In the condition of no-added exogenous cadmium, J85 mycelium average growth rate was higher than that of J77. When the concentration of cadmium was 0～2mg/L, J77 mycelium growth rate was higher than that of J85. When the concentration of cadmium was in the range of 2～200mg/L, the mycelium growth of two strains were inhibited. With the increase of exogenous cadmium addition, mycelium biomass of two strains firstly increased, and then decreased. In the experiment condition, J77 mycelium biomass of J77 was higher than J85.2. With the increase of exogenous cadmium addition, the MDA content and enzyme activities of two strains firstly increased, and then decreased. In the conditions of no-added exogenous cadmium, mycelium MDA content of J85 increased by 32.44% than that of J77. The increase of MDA content for J85 was significantly higher than that ofJ77 with the increase of cadmium concentration. Compared to J77, the concentration of exogenous cadmium was lower when J85 mycelium enzyme activities reached the maximum value.3. Mycelium morphology and structure of J77 and J85 all changed under different exogenous cadmium stress. When cadmium concentration was 100mg/L, their mycelium morphologies seriously damaged. While cadmium concentration was 0.5～2mg/L, their mycelium only had small changes. J85 mycelium began to become transparent with the increase of cadmium concentration, but the mycelium of J77 only showed more shrinkage and distortion. When the cadmium concentration reached the maximum value, the mycelium of J85 cracked, and the inclusion spilled.4. Without the exogenous cadmium addition, the cadmium content of J77 mycelium was lower than that of J85. The cadmium contents of J85 mycelium all were higher than those of J77 with the increase of cadmium concentration.5. With the increase of exogenous cadmium stress, the fruiting bodies yield of two A. blazei firstly increased and then decreased. In the experimental condition, the inhibition rate of fruiting body yield for J85 was higher than that of J77.6. When the cadmium concentration was 0～2mg/kg, the spores length, width and the cystic diameter of two strains all increased, and their spores and cystic morphology had no obvious variation. When cadmium concentration was higher than 2mg/kg, the spores and cystic morphology of two strains began to change, their shapes and sizes were subject to inhibition. When the cadmium concentration reached the maximum value, the spores and cystic morphology of two strains obviously changed. Without the exogenous cadmium addition, the spores length, width and cystic diameter of J85 were greater than that of J77.7. Under the exogenous cadmium stress, the SOD, POD, CAT, APX enzyme activities and MDA content of two strains firstly increased and then decreased. But there was difference in exogenous cadmium concentration between them while the enzyme activities reached the peak, and the cadmium concentration for J85 was lower than that of J77. The MDA content of in fruiting bodies of J85 was higher than that of J77.8. Zn content of two strains decreased with increase of cadmium concentration. The contents of Cu, Fe and Mn of them firstly increased and then decreased. There was significant positive correlation between Mg and exogenous cadmium concentration. When the cadmium concentration reached maximum, Mg content also peaked. Ca content showed a trend of down-up-drop with increase of cadmium concentration. With increase of cadmium concentration, Except for Zn, the other five mineral elements of J85 all were lower than those of J77. There was obvious effects of cadmium stress on carbon, nitrogen, phosphorus and potassium absorption. Carbon content of them significantly decreased with the increase of cadmium concentration, and nitrogen and potassium content firstly increased and then decreased, cadmium content of two strains increased. When the cadmium concentration reached maximum value, the cadmium content of their fruiting bodies also peaked. Without the exogenous cadmium addition, cadmium content of the fruiting bodies for J85 increased by 32.44% than that of J77. When cadmium concentration reached 50mg/kg, cadmium content of J85 increased by 68.98% than that of J77.9. Eight kinds of essential amino acids and two kinds of semi-essential amino acids in the fruiting bodies of J77 and J85 were detected in the experiment. The total amino acids and essential amino acids of J85 were higher than those of J77. With the increase of cadmium concentration, there was obvious difference in the total amino acids and 17 kinds of amino acid content between J77 and J85. According to FAO/WHO standard, E/T of J85 was lower than FAO/WHO standard when cadmium concentrations were higher than lOmg/kg. The E/T, E/N of J77 was lower than FAO/WHO standard when cadmium concentrations exceeded 20mg/kg.10. The correlation analysis results showed that,there were significant negative correlation between the growth speed, mycelium biomass, SOD enzyme activity of two strains mycelium and two fruiting bodies agronomic characters, yield, SOD enzyme activity, Zn, Mn, N, K and carbon content and exogenous cadmium concentration. The of two fruiting bodies There was also significant positive correlation between cadmium content and Mg content of their mycelium. For J85, The MDA content had positive correlation with cadmium concentration. But t there was no significant correlation among other indexes. |
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