Blight Resistance
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Sárpo varieties have been in field trials and have been tested in the laboratory at many sites in U.K. and Europe over the last 10 years. Field trials at Henfaes have clearly shown that Sárpo clones have a unique combination of high resistance to both late-blight disease and major virus diseases. Resistance is not absolute as a restricted development of blight can be observed at the end of the season but yield is unaffected. Our Sárpo varieties have been grown for many years throughout UK and in many parts of Europe and have survived the impact of severe late-blight attack, as in 2007 when other so-called resistant varieties failed to produce a crop. How Are Sárpo Varieties Produced? Blight resistance was bred into our varieties by crossing with accessions of wild Solanum species having high resistance to blight in foliage and tubers. Our aim is to select durable varieties which can produce good marketable crops in wet seasons without the protection of fungicides or with minimal fungicide use. It is thus essential to challenge our selections with as many populations of blight pathogen as possible so that the kind of resistance which overcome by certain strains of the pathogen can be identified and eliminated. Our best varieties are resistant to all known strains of blight. Promising clones have been selected in the laboratory and in the field. Annual trials at Henfaes and at many other sites in UK and Europe have scored foliage and tuber blight and compared scores to those of standard varieties. The protocol used is that agreed by members of EUCABLIGHT, an EU Concerted Action of European Blight Researchers. Sárpo Mira has been used as a standard resistant variety by many European researchers. In some of our field trials, natural blight infection is encouraged and in others, plots are inoculated with known strains of the pathogen. Using EUCABLIGHT protocols, the performance of a variety in foliage blight trials relative to standard varieties is converted to a 1-9 score where 1 is the most susceptible and 9 is totally resistant. In addition, detached leaflets are inoculated with a range of known isolates of the pathogen in the laboratory; infection, colonisation and sporulation are scored in these tests to find out if non-indigenous strains can overcome the resistance. Tuber blight is assessed at harvest following foliage blight trials and also in the laboratory using protocols agreed by the EUCABLIGHT network. Again as many strains of blight as possible are used in these assessments. |
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