Biochemical and ultrastructural features related to male sterility in the dioecious species Actinidia deliciosa

Kiwifruit (Actinidia deliciosa var. deliciosa) is a dioecious plant whose f lowers are morphologically hermaphrodite yet functionally unisexual. The ob jective of this study was to investigate the male sterility of female flowe rs in kiwifruit through an integrated biochemical and cytohistological appr oach. Hi,gh levels of free and trichloroacetic acid (TCA)-insoluble conjuga ted polyamines (PAs) were found to be associated with pollen degeneration. Carbohydrate levels greatly differed when comparing mature to degenerated p ollen from the anthers of male-fertile and male-sterile flowers; respective ly. In the cytoplasm, carbohydrates strongly decreased in the degenerated p ollen, whereas in the cell wall, their levels remained consistent. The dege nerated pollen showed a poorly sculptured sexine, an anomalous nexine, and an intine consisting of a single stratum only. Through in vitro culture of anthers from male-sterile plant, the pollen occasionally reached the binucl eate stage. The structural anomalies in the pollen of the male-sterile plan t and the alterations in PA and carbohydrate contents, together with the re sults of the in vitro anther culture, suggest that the male sterility in th is species could be under both sporophytic and gametophytic control. (C) 20 01 Editions scientifiques et medicales Elsevier SAS.