دانلود گزارش کارورزی و کار آموزی

چکیده : 

Climate change effects on Fusarium oxysporum f.sp. lactucae (FOL) on lettuce plants grown under simu-lated climate change were studied. An artificial growing substrate was infested with FOL to reach a finalconcentration of 1 × 104CFU g−1of substrate. A non infested tank was used as control.Subsequently, 32 pots (2 l each) were prepared from the infested tank and other 32 pots were preparedfrom the non infested tank (control). Lettuce plants were then transplanted into the pots and grownin phytotrons under four simulated environmental conditions: (1) 800 ppm CO2, 22–26◦C; (2) 800 ppmCO2, 18–22◦C; (3) 400 ppm CO2, 22–26◦C and (4) 400 ppm CO2, 18–22◦C. Substrate samples were col-lected from each phytotron at 7, 14, 21 and 28 days after transplanting. Plate counts, enzymatic assays,and polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) analyses were per-formed to evaluate the effect of climate change on the microbial population. The abundance of Fusariumspp. and the severity of Fusarium wilt of lettuce varied significantly as a consequence of increased tem-perature (22–26◦C). Increased CO2levels showed no effect on the severity of Fusarium wilt of lettuceand on the abundance of Fusarium spp. On the other hand, the total bacterial abundance was reduced atelevated CO2concentration (800 ppm). PCR-DGGE fingerprints of the ascomycete community obtainedfrom DNA directly extracted from infested substrate samples did not change as a consequence of elevatedtemperature and CO2.Enzymatic activities were not affected by the elevated CO2level. Our study indicates that the CO2concentration used in our experiment had no detectable impact on Fusarium wilt of lettuce. Only tem-perature influenced all observed parameters, but did not affect the fungal species diversity. Other factors,such as nutrient limitation and the effect of plant species needs further study.© 2013 Elsevier B