The waterberry stem necrosis disorder in grapes and its relationship with elevated putrescine levels and low potassium content

Rafael Ruiz S.1 y Stella Moyana A.1

In orderto evaluate a possible association between putrescine and a physiological disorder known as bunch stem necrosis (waterberry), rachis (main axis and branches) from clusters of two seedless varieties, with and without symptoms were colected. Rachis were separated in three parts: necrotic apical tissue, intermediate and basal tissue containing the peduncle. The analysis showed significantly higher levels of putrescine (two to ten times) in necrotic rachis compared with normal tissues. In the same way putrescine levels increased from the basal area (apparently wealthy) toward the necrotic apex. Ammonium content also increased several times in affected rachis but there was no detection of any consistent increment in the direction of necrotic area. Consecuently, it appears that putrescine would be more involved with the problem of bunch stem necrosis than ammonium. Mineral analysis showed low K levels in tissues from necrotic clusters. The relatioship between low K level and putrescine acumulation is discussed.

Keywords: table grapes, waterberry, putrescine, potassium, nutritional disorders.
1 Estación Experimental La Platina (INIA), Casilla 439, Correo 3, Santiago, Chile.