27 SEED TESTING INTERNATIONAL APRIL 2026 • RULES DEVELOPMENT Method Validation Report for Application of the Radicle Emergence Test to Allium cepa Hulya Ilbi1, G.V. Jagadish2 and Alison A. Powell3 1Department of Horticulture, Ege University, Bornova, Izmir, Türkiye 2IndoAmerican Hybrid Seeds, Bengaluru, India 3Aberdeen University, Aberdeen, UK THE RADICLE EMERGENCE (RE) TEST WAS CARRIED OUT ON SEED LOTS OF ALLIUM CEPA by five laboratories from India and six laboratories within Europe. Problems with seed supply resulted in the Indian laboratories testing seven seed lots, while the European laboratories tested only three of the same lots. The test was carried out at 20 °C with RE assessed as a radicle ≥2 mm after 72 h. Data were analysed for the seven lots tested by five Indian laboratories, and for the three lots tested by both Indian and European laboratories. Low RE results compared to all other laboratories resulted in one laboratory from Europe being omitted from the analysis. The Indian laboratories consistently identified the same lots as having high RE (high vigour) and low RE (low vigour) and both the repeatability and reproducibility data were acceptable. Comparison of the RE for three seed lots tested by ten laboratories revealed similar RE values to those obtained by the Indian laboratories alone and both the repeatability and reproducibility data were acceptable. These analyses support the inclusion of onion as a species to which the RE test can be applied. Introduction The RE test is an ISTA vigour test currently validated for five crop species (Zea mays, Brassica napus, Raphanus sativus, Triticum aestivum subsp. aestivum and Glycine max). Many papers have reported correlations between a RE count and vigour (Powell, 2022) including two Allium species, Allium cepa and Allium porrum. RE counts of A. cepa predicted both seed storage potential (Demir et al., 2022) and field emergence (Ilbi, unpublished data, Appendix 1), while counts for A. porrum predicted early and final emergence and seedling fresh and dry weight (Ermis et al., 2015). The aim of this comparative test was to determine if RE counts of A. cepa are repeatable and reproducible for potential inclusion of this species in the International Rules for Seed Testing (ISTA Rules) as one to which the RE test can be applied. Materials and Methods Seed Material This comparative test initially aimed for laboratories in India and Europe to test seed lots that originated from seed companies in both India and Europe. Seed lots of commercially available onion seed were obtained from Nunhems Seeds and IndoAmerican Hybrid Seeds. Four seed lots from Nunhems were sent to the test organisers in Türkiye (Dr Hulya Ilbi) and India (Dr G.V. Jagadish). However, the germination of one lot on receipt had fallen to below commercially acceptable standards and was therefore not used. IndoAmerican Hybrid seeds provided a further four lots which were also sent to Türkiye. Unfortunately, these seed lots were held by the Turkish customs and could not be released without substantial payment and phytosanitary analysis in the Quarantine Department of the Turkish Ministry of Agriculture. As a result the comparative test was completed using three lots from Nunhems in laboratories in Europe and seven lots in Indian laboratories (three lots in common with Europe, four lots supplied by IndoAmerican Hybrid Seeds). Participating Laboratories Coded samples were sent to the laboratories shown in Tables 1 and 2. Testing Procedure On receipt, participants placed seed in a moisture-proof bag at <10 °C until use and completed the test within 2 weeks of receiving the seed. They were advised to consult the general guidelines for completion of the RE test as found in the ISTA Rules, section 15.8.4. To complete the test for onion: 1. Each of four replicates of 50 seeds for each seed lot were placed on two germination papers (Whatman No: 5), that were held in 90 mm- diameter Petri dishes and had previously been moistened with 4 ml distilled water. In Europe: One laboratory in Europe used an alternative filter paper and care was taken to ensure that all the water was absorbed into the germination paper, and there was no free water on the surface. Laboratories used a 12-h light / 12-h dark regime, and the test was set up at the beginning of the light period of that regime. In one laboratory, where an automated 12/12-h light regime was not possible, an 8/16-h regime was used. Laboratory Contact person Sakata Seeds, Bengaluru, India Ms Sunitha Namdhari Seed, Bengaluru, India Dr Prashanth East West Seeds, Hyderabad, India Ms Mohini IndoAmerican Hybrid Seeds, Bengaluru, India Ms Veena Nunhems Seeds, Hyderabad, India Ms Muktha Pathre Table 1. Laboratories in India who tested seven seed lots of onion in the radicle emergence comparative test: three seed lots from Nunhems and four seed lots from IndoAmerican Hybrid Seeds Laboratory Contact person Department of Horticulture, Ankara University, Türkiye Dr Ibrahim Demir Official Seed Testing Station for Scotland, Edinburgh, UK Gillian Musgrove Official Seed Testing Station for England and Wales, Cambridge, UK Gillian Durrant Finnish Food Authority, Finland Jaana Laurila Department of Horticulture, Ege University, Türkiye Dr Hulya Ilbi LaRAS, University of Bologna, Italy Dr Enrico Noli SNES, GEVES, France Valerie Blouin Table 2. Laboratories in Europe who tested three seed lots of onion from Nunhems in the radicle emergence comparative test
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