Abstract:

In order to better understand the impact of newly occurred cankers on soluble starch accumulations in poplar roots, and to further assess trees’ vigor along to the change of starch reserves in roots, Populus euramerican ‘zhonglin 46’ with new canker were selected during 2008 growing season and marked according to disease severity indices and their roots were collected at dormancy period in 2008, growing season in 2009 and dormancy in 2009 from 6 temporary plots in Qingfeng County, respectively. Starch in roots was determined using iodine colorimetric method. Starch of diseased trees was not significantly different compared to that of healthy trees at 2008 dormancy (F=0.535, P=0.660). Starch content was significantly different among roots of healthy, slightly diseased, intermediately diseased and severely diseased trees in 2009 growing season (F=3.668, P=0.02) and 2009 dormancy (F=3.335, P=0.035), particularly a significant reduce of starch was found among those severely diseased trees; while starch content in intermediately diseased trees was significantly higher than that of slightly diseased and severely diseased trees in 2009 dormancy. The t-test indicated that starch content of severely diseased trees significantly decreased during 2009 growing season (t=5.197, P＝0.001) and dormancy period (t=3.219, P＝0.008) compared to 2008 dormancy. At the same time, no significant difference of starch content change was found in healthy and slightly diseased trees. Interestingly, an increment of starch content was found in intermediately diseased trees, while the change was not significantly. This study revealed that the change of starch content was affected by severities of canker in different ways. Starch content in severely diseased trees reduced significantly and further reduced trees’ vigor, while slightly disease trees’ vigor was not affected due to insignificant decreases of starch reserves. A slightly increase of starch reserve was observed in those intermediately diseased trees which most likely meant a slight increase of vigor.