Effects of simulated hail injury on potato stem anatomy and yield

Abstract

The principle objective of this study was to define the effects of defoliation and stem bruising on potato tuber yield. Secondary objectives were to determine difference in cultivar response and the influence of bruising on the potato stem vascular system. The work was supported in part by the National Crop Insurance Association. The data obtained will be used by insurance personnel in conjunction with loss tables to estimate losses. The influence of defoliation, bruising and plant age on potato yield was determined in a factorial experiment with three replications. Four potato cultivars were compared with a standard cultivar ('Russet Burbank') involving injury at three stages of growth. Injury treatments were applied by hand. Yield loss relative to non-injured plants was determined at the end of the season. Photomicrographs were taken of bruises on stem sections at one, three, five and seven weeks after bruising to follow changes in the vascular system. Defoliation resulted in the removal of active photosynthetic leaf area. Bruising disrupted the plant canopy and interrupted the vascular transport system. Both types of injury reduced total and market yields with larger losses resulting from more severe injury. However, losses were not linearly related to the degree of injury. This was attributed to the physiological and morphological regenerative potential of the potato plant. When defoliation and bruising were applied in different combinations losses were additive. Within the scope of this study, the most sensitive stage of plant development was about six to seven weeks after emergence. Three early maturing cultivars responded to injury significantly different than the 'Russet Burbank' cultivar when injured three weeks from emergence. However, they responded similarly when injured six and nine weeks from emergence. Thus, loss charts prepared for the 'Russet Burbank' cultivar could be used later in the season with the three early maturing cultivars. Photomicrographs taken of bruised stem sections showed that the potato plant was able to withstand injury and still maintain a certain amount of functional vascular system. This is because the vascular system is well protected by various support cells, and most of the damage to the stem was absorbed by these cells. The vascular system is also complex with a high degree of anastomosing between its leaf traces.