冬穫りキャベツの凍害発生および耐凍性獲得におよぼす気温の影響

Abstract

It has been known that the occurrence of head rot is due to the multiplication of bacteria on cabbage which is pre-disposed by cold injury.Relations among the bacterial head rot on cabbage harvesting in winter at the Miura Peninsula and the meteorological elements in growing period were investigated from 1983 to 1992 except 1987. Percentage or index of head rot occurrence were determined using from 500 cabbage plants in each year. The meteorological data were obtained from AMeDAS (automated meteorological data acquisition system) data observing in Miura city.The cold hardiness of the third leaf from outside of the head was investigated during harvesting time for 2 years. Cold hardiness, using ‘LT50’ (equation 2 and 3) which determines the frost-killing temperature required to kill 50% of the cells of cabbage leaves which were under the condition of low temperatures (-5, -7.5 and -10°C) for 2 hours in low temperature water bath were calculated.The results obtained as follows:1. There were high correlations between the air temperature in the middle of November and the head rot occurrence in cabbage. The higher the mean air temperature in the middle of November than the normal, the higher the head rot occurrence.2. There were no relation between the duration of sunshine or the amount of precipitation and the head rot occurrence in cabbage.3. The time of increased cold hardiness of cabbage leaves was not the same. However, the lowest ‘LT50’ was about -10°C in each year.4. There were correlations between ‘LT50’ and the accumulated daily mean air temperature for over 4 days. The difference of ‘LT50’ was more than 4°C during harvesting time, because of the differences in the mean daily air temperature when the cabbage were harvested.5. These results indicates that if the mean air temperature in the middle of November was higher than normal, the countermeasure by covering cabbage is necessary.