Digital Image Analysis of Low-Temperature Responses in Sweet Corn Hybrid Seedlings

Breeding for stress-tolerant hybrids begins with screening germplasm for tolerant genotypes. We employed a non-destructive and objective method to evaluate the low-temperature response of sweet corns at the seedling stage, using a digital image analysis. It was estimated using summed leaf area, a new parameter defined as the sum of the leaf area measured from images taken at different angles. The summed leaf area, SPAD, shoot and root fresh weight, and total root length were significantly different among hybrids. The group mean of sugary endosperm type was significantly higher than that of shrunken type for all traits but SPAD. For the summed leaf area, the top three ranked hybrids were from the sugary type, but the area for the following three hybrids from the shrunken type did not differ from that for the first three hybrids. The summed leaf area was correlated with SPAD (r = 0.49 **), shoot (r = 0.99 **) and root (r = 0.93 **) fresh weight, and total root length (r = 0.76 **). Phytoglycogen in seeds only had a significant correlation (r = 0.46 **) with the area. The summed leaf area of only one hybrid differed between normal- and low-temperature conditions. The low-temperature response based on the summed leaf area was reflected in the field condition, with a few exceptions. The results suggest that the summed leaf area via digital image analysis can be used to evaluate low-temperature response in sweet corns.