ブドウ果実の着色に及ぼす成熟期の紫外光照射の影響

The objective of this study was to investigate the effect of irradiation with ultraviolet-A (UV-A) on berry growth, the total soluble solids and titratable acidity of the juice, and anthocyanin contents of berry skins in 'Gros Colman' (Vitis vinifera) and 'Pione' (V.labruscana × V.vinifera) grapes. Clusters of mature 'Gros colman' and 'Pione' vines grown in glass or plastic film houses were irradiated with UV-A lamp in the daytime for 10 and 4 weeks during maturation, respectively. In 'Gros Colman' grapes, irradiation with UV-A markedly increased anthocyanin content in berry skins with the days after irradiation, and anthocyanin level in the skin of clusters irradiated with UV-A was four times that of control clusters at four weeks after treatment. At harvest, berries from exposed-side of UV-A irradiated clusters had the highest anthocyanin in the skin followed in the skill followed in descending order by exposed-side of non-irradiated clusters (control), and non-exposed-side of control and UV-A irradiated clusters. By contrast, anthocyanin content in the skin of 'Pione' grapes was not affected by irradiation with UV-A throughout the experiment. In both cultivars, no significant difference in either berry growth, the contents of total soluble solids or titratable acidity of the juice were observed among the treatments. Based on the results, the relationship between coloration og grape berries and UV-A irradiation during maturation is discussed.

ブドウ果実の着色に及ぼす紫外光の影響を明らかにするため，成熟開始後に‘グロー・コールマン’では10週間，‘ピオーネ’では４週間，UV-Aを昼間だけ照射した．‘グロー・コールマン’の場合，照射果房のアントシアニン含量は，処理開始１週間後には対照果房よりも多くなり，４週間後には対照果房の約４倍に達した．収穫時のアントシアニン含量は，照射果房の照射側で最も多く，次いで対照果房の照射側，および照射果房と対照果房の無照射側の順であった．しかし，‘ピオーネ’では処理期間を通して，UV-A照射によるアントシアニンの増加は認められなかった．いずれの品種においても，UV-A照射は果実重，果汁の糖および酸含量には影響しなかった．以上の結果を基に，ブドウ果実の着色とUV-A照射との関係について考察した．