ISHS Acta Horticulturae 587: International Symposium on Asian Pears, Commemorating the 100th Anniversary of Nijisseiki Pear
INTERNAL BARK NECROSIS IN 'NIITAKA' PEAR |
| Author: | G.C. Song |
| Keywords: | Pyrus pyrifolia, NO3-N, NH4-N, outer tissue of the cambium, xylem, pith tissue |
| Abstract:
The potential cause of internal bark necrosis (IBN) of ‘Niitaka’ pear trunks was determined. The symptoms were similar for all pears growing in orchards of different locations. Growth characteristics of trees as well as soil fertility were examined in a ‘Niitaka’ pear orchard where the IBN symptoms were severe. Soil pH was not different from unaffected sites, but NO3-N and NH4-N contents of the soil were very high. Shoots were numerous and long, but shoot growth lasted till late August. Compared with other nutritive elements, nitrogen content was very high in the outer tissue of the cambium, low in pith tissues but was not different in the xylem. Internal bark necrosis was induced in potted trees by applying NO3-N and NH4-N, at rates of 2 or 4 times higher than the recommended levels. Leaf blackening was induced and defoliation occurred. This was followed by internal bark necrosis of the trunk and finally death of the whole plant. Cell walls were collapsed, vacuoles were filled with unknown materials, and middle lamellas were thickened. | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
