Preliminary Observations on the Phytosanitary Status of the Croatian Satsuma Mandarin (Citrus unshiu Marc.) Collection

Abstract

Preliminary surveys of citrus field trees in Croatia showed their unsatisfactory sanitary status especially with regard to the presence of Citrus tristeza virus (CTV) even though symptoms in the field are mostly absent. The highest CTV incidence was recorded in the Satsuma mandarin (Citrus unshiu Marc), commercially the most important citrus in the country. The Satsuma collection orchard was founded in the year 2005 at the Institute for Adriatic Crops and Karst Reclamation. It encompasses 12 mandarin cultivars and 51 Satsuma clones from different sources. With the aim of assessing the phytosanitary status of Satsuma collection, biological indexing of all 12 cultivars for principal virus and virus-like diseases was performed. Seven citrus bioindicators were used ; Mexican lime, Madame Vinous and Pineapple sweet oranges, Sicilian sour orange, CRC grapefruit, Troyer and Carrizo citranges. Herbaceous hosts (white sesame, red kidney bean and Chenopodium quinoa) were also used for cool-climate pathogen detection. Serological tests (ELISA and DTBIA) were performed for CTV and Citrus psorosis virus (CPsV) directly on 18 representative clones and on Mexican lime and Madame Vinous indicators. CPsV was not detected by serology while only 2 clones were CTV-negative, both in biological and laboratory tests. Furthermore, the most severe CTV strains displaying stem-pitting and seedling yellows in grapefruit and sweet oranges were found in 4 tested clones. No biological indication of other disease presence in the collection has been found so far. Further testing of the collection Satsumas is under way, as well as the sanitation of the most important cultivars.