Causal Factors and Control of the Necrotic Disorder of Berries in 'Muscat of Alexandria' Grape

葡萄浆果的坏死性疾病，在日语中被称为“Shukuka-byo”，被认为是由于生理衰竭，但预防这种疾病的方法尚不清楚。由于其最初的褐变症状出现在维管束上，且一些抗生素治疗的预防效果较好，笔者认为这可能是一种未知生物感染的血管疾病。扫描电镜观察到，在受损浆果的筛元和邻近的花托和基部薄壁细胞中观察到许多卵圆形到球形的颗粒，但在健康浆果中很少见到。颗粒直径大都在0.5 ~ 1.0 μ m之间，有大有小，有光滑有粗糙。在组织接种的培养基上，无性系克隆的颗粒大小为0.2 ~ 2.0 μ m，在受精卵离心液的沉淀部分中，无性系克隆的颗粒大小为0.2 ~ 1.8 μ m。但TEM未发现任何微生物，只有一些0.2-1.0 mm的圆形结构，没有清晰的膜和内部，推测是被分解的线粒体。木质部汁液中含有一些0.05 ~ 0.2微米的带膜生物样颗粒。mlo样菌落经常在健康和/或成熟阶段的浆果和花托的组织周围产生，但不会在顶端培养的葡萄藤的组织周围产生，这些葡萄藤种植在网状温室中，免受叶蝉的侵害，没有表现出任何坏死障碍的症状。菌落在移植后不再生长，也不能通过组织上的透析用纤维素膜生长。液体培养基离心12000 (G)后，从沉淀部分颗粒中检测核酸。除了对试管无菌培养插枝进行基础处理外，多次接种均未证实颗粒的致病性。

The necrotic disorder of grape berries, so called 'Shukuka-byo' in Japanese, has been considered due to physiological breakdown, but prevention of this disorder is yet obscure. Authors supposed that it should be a vascular disease infected by unknown organisms because of its first browning symptom appeared on vascular bundles, and preventive effectiveness of some antibiotic treatments.Numerous oval to spherical granules were observed in sieve elements and adjacent parenchymatous cells at receptacles and the basal portion of suffered berries, but rare in healthy berries through SEM. The granules were mostly ca. 0.5-1.0 mum of diameter, but some were smaller and others larger, and some were smooth in its surface but others rough. Rough granules of 0.2-2.0 mum were observed in the clonies on the medium inoculated with tissues, and smooth granules of 0.2-1.8 mum were also observed in the precipitated fraction of centrifuged juice of suffered berries. But we could not find any microorganisms through TEM, except some orbicular structures of 0.2-1.0 mum without clear membrane and interior, which were supposed to be broken down mitochondria. Xylem sap contained some organism-like granules of 0.05- 0.2 mum with membrane. MLO-like colonies were frequently produced around the tissues of healthy and/or suffered berries and receptacles on the StageII to maturation, but not around the tissues from the tip-cultured grapevines, which were planted in a netted greenhouse protected from leafhoppers and did not show any symptoms of the necrotic disorder. The colonies did not grow any more by its transplanting, and also did not grow through the cellulose films for dialysis laying against the tissues. Nucleic acids were detected from the granules in precipitate fraction after 12,000 centrifugation(G) of liquid culture medium. Pathogenisity of the granules was not elucidated by several inoculation, except a instance of basal treatment to the aseptic cultured cuttings in tubes.