ARI Biennial Review for 2018-2019

Citrus certification programme A mandatory certification programme has been established and functioning since the mid 1990’s. The responsibility for the implementation of the relevant legislation rests with a seven-member Board under the Minister of Agriculture. The foundation or pre-basic block is kept and maintained under insect-proof screen by the Agricultural Research Institute, whereas the multiplication and mother blocks, protected also under insect- proof screen, are maintained by the Department of Agriculture. In addition, the private nurseries are obliged to keep their mother plants and the production of seedlings and budded treelets also under screen. The foundation block provides with virus-tested material the mother blocks of the Department of Agriculture, which in turn provide with budwood the private nurseries or directly the growers. Citrus budwood, which is introduced from overseas sources, is kept in a post-entry quarantine station and undergoes thorough indexing for the known virus and virus-like diseases before entering the foundation block. Local varieties are being cleaned from the known virus problems by micrografting. All virus-free material, which was either selected, or imported by the Horticulture Section of the Institute or produced locally so far by micrografting, is maintained in a pre-basic plantation under double insect-proof screen at the Agricultural Research Station of Zygi. To the present 60 citrus accessions are included in the plantation and are kept in clean state by application of strict sanitary measures and regular indexing, in conjunction with optical observation for either fungal problems or genetic aberrations. The plantation provides with citrus material the basic or mother plantations of the Department of Agriculture and the experimental glasshouses of the Institute. (T. Kapari-Isaia, L.C. Papayiannis) Production of healthy local citrus propagating material For several commercial varieties, it is possible to reintroduce presently healthy material from overseas Citrus Production Centers. However, this always includes the risk of the introduction of new unknown diseases. In addition, for local varieties there is not such possibility. For these reasons, it was decided to employ contemporary techniques, as micrografting in vitro to free from virus and other disease problems valuable local citrus varieties and/or clones, including ‘Lapithou’ and ‘Polyphori’ lemon, ‘Arakapa’ mandarin, local ‘Jaffa’ orange and others. The micrografting in vitro technique was used in Cyprus since 2000 to free from virus and other pathogens valuable local citrus varieties and/or clones. A survey in commercial groves was conducted for selection of elite mother plants of citrus, including ‘Polyphori’ and ‘Lapithou’ lemon ( Citrus limon Burm f.), ‘Jaffa’, ‘Siekeriko’ and ‘Aematoysiki’ orange ( C. sinensis L.), ‘Arakapas’mandarin ( C. reticulata Blanco ), ‘Frappa’ ( C. grandis (L.) Osbeck ), ‘Bergamot ‘( C. bergamia Risso & Poit. ), ‘Coumantantas’ ( C. comandatore ) and ‘Pummelo’ ( C. maxima ). All mother plants were tested for viruses and viroids by biological indexing, by ELISA for CTV, and by RT-PCR for viroids. The standard procedure of shoot-tip grafting technique was used for elimination of viroids and CPsV in the selected citrus isolates. Micrografted plants, re-grafted on sour orange seedlings in vivo , and successfully established and transferred to the glasshouse, were tested 6-9 months later for the viruses and viroids present in meristem donor mother plants. (T. Kapari-Isaia, L.C. Papayiannis) Elimination of citrus pathogens from infected citrus plants by micrografting in vitro In vitro micrografting technique has been used for sanitation of citrus species and varieties infected by Citrus tristeza virus (CTV) and/or citrus viroids. Several citrus tree varieties including the lemon varieties ‘Adamopoulou’ and ‘Verna’ and the mandarin varieties ‘Clasuelina’ and ‘Page’ were selected. All trees were tested for viruses and viroids by biological indexing, by ELISA for CTV and CPsV, and by RTPCR for viroids. They were all found free of CPsV, CVV, concave gum and impietratura. The micrografting technique in vitro was used for elimination of viroids and CTV in the selected citrus isolates. Micrografted plants were re-grafted on sour orange seedlings in vivo, or were potted and those which were successfully established were transferred to the glasshouse. They were tested 6-12 months later for CTV and viroids present in meristem donor mother plants. One or more plants produced by micrografting from all mother plants were found free of CTV and/or viroids. (T. Kapari-Isaia, L.C. Papayiannis) 42 PLANT PROTECTION