We investigated the genetic characteristics and fruit quality of Hetsuka Daidai, a citrus that is a specialty of the southern part of the Osumi Peninsula in Kagoshima Prefecture. Based on the results of CAPS (cleaved amplified polymorphic sequence) analysis, Hetsuka Daidai had cytoplasm derived from pummelo and was closely related to Kabusu (sour orange), Natsudaidai, and Kimikan. No difference was observed in the CAPS genotype of either nuclear or chloroplast among the four Hetsuka Daidai accessions used in this study. After a four-year investigation of the fruit quality, the green color remained on the rind and the titratable acidity (TA) was about 4% from the end of September to October during the main period of harvesting. The fruit weight continued to increase with maturity and was about 100g in late October. Regarding the organic acid composition, the rate of citric acid was about 97% and the ascorbic acid content was 19.2 - 28.0 mg･100 mL^-1. Limonene had the highest aroma component at 81.2%, followed by 9.8% of γ-terpinene, 2.6% of β-myrcene, 1.4% of α-pinene, 1.2% of p-cymene, and 1.1% of sabinene. No aroma components, characteristic of Hetsuka Daidai, were found. Even in the sensory evaluation of the aroma, we could not confirm the items characteristic of this fruit. From these results, it was suggested that the scent balance was different from that of other citrus fruits and that it was unique to Hetsuka Daidai.

In this study, the air temperature and leaf temperature of ‘Bacon’ avocado trees grown outdoors were measured in December and January to investigate the relationship with the occurrence of cold damage. Temperatures were recorded four times, three of which were clear weather with strong radiation cooling, and cold damage such as browning of leaves and defoliation had occurred. The minimum air temperatures when cold damage occurred were (from highest to lowest) -3.1 ℃, -4.5 ℃, and -5.1 ℃. The mean leaf temperatures in the early morning (at 4:00–7:00 am) on these days were -5.3 ℃, -6.9 ℃, and -6.9 ℃ respectively, and the respective differences between the mean leaf temperature and minimum air temperature were 2.2 ℃, 2.4 ℃, and 1.8 ℃. Based on these results, on early winter mornings with clear weather, the leaf temperature of the ‘Bacon’ tree was approximately 2 ℃ lower than the minimum air temperature. Leaf damage occurred when the mean leaf temperature was -5.3 ℃ or lower, which is consistent with the leaf temperature at which cold damage reportedly occurred in a previous indoor study. Our results suggest that the risk of cold damage in ‘Bacon’ avocado tree increases when the daily minimum air temperature falls below -3 ℃.