Abstract

We investigated the patterns of freeze injury in dormant 'Changhowon Hwangdo' peach fruit by observing the extent of browning and germination of the branches that were treated with freezing temperature sets simulating the process of natural freezing incidences in orchards. Under the treatment of freezing temperature of $-15^{\circ}C$, the browning ratios were 15% for flower bud and less than 3% for both leaf bud and cambium. Under the $-20^{\circ}C$ treatment, the browning ratios were 40% for both flower and leaf buds and 1% for cambium. The browning ratios were 86%, 68% and 40% respectively for flower bud, leaf bud, and cambium under the $-25^{\circ}C$ treatment. All the samples showed 100% browning ratio under the $-30^{\circ}C$ treatment. The budburst ratios of leaf buds were 85%, 66%, 32%, and 0% under the -15, -20, -25 and $-30^{\circ}C$ treatments, respectively. The branches of peach fruit treated with the same freezing temperature showed different responses depending on the sampling date. In January the browning ratio was low and the budburst ratio was high whereas in February the opposite was the case, showing vulnerability of peach trees to low temperature after endo-dormancy release.

실제로 동해가 발생한 해의 기온 경과양상에 근거한 저온처리조합을 만들어 복숭아 나무 '장호원황도' 품종의 휴면지에 처리하여 갈변정도와 발아를 관찰함으로써 시기에 따른 휴면지의 부위별 동해양상과 동해유발 온도를 파악하였다. 갈변율의 경우 $-15^{\circ}C$에서 꽃눈은 10%, 잎눈과 형성층은 3% 미만이었으며 $-20^{\circ}C$에서는 꽃눈과 잎눈은 40%, 형성층은 1%이었다. $-25^{\circ}C$에서의 갈변율은 꽃눈과 잎눈이 86%와 68%, 형성층은 40% 이상이었고 $-30^{\circ}C$에서는 모든 부위에서 100% 갈변되었다. 잎눈 발아의 경우 대조구(무처리)의 발아율을 100%로 두었을 때 $-15^{\circ}C$에서는 85%, $-20^{\circ}C$에서는 66%, $-25^{\circ}C$에서는 32%의 상대발아율을 보였으며 $-30^{\circ}C$에서는 전혀 발아하지 못했다. 동일한 저온처리의 경우 휴면심도가 깊은 시기로 알려진 1월 말에 채취한 시료에서 갈변율은 낮고 발아율은 높았다. 2월 이후에는 갈변율이 높고 발아율이 낮아 휴면해제 직후가 동해위험에 더 취약한 것으로 나타났다.

Keywords

• Freeze injury;
• Peach tree;
• Browning;
• Budburst;
• Dormancy release;
• Global warming