NOVEL SOURCES OF RESISTANCE TO ERWINIA AND FUSARIUM IN POTATO
AK LEES, JE BRADSHAW, M DE MAINE and HE STEWART
Scottish Crop Research Institute, Invergowne, Dundee DD2 5DA, UK
Background and objectives
Resistance to soft rot has been found in wild and other cultivated Solanum species but, even where such species hybridise with subsp. tuberosum, poor adaptation is a problem with regard to their use in European conditions . This study details the assessment of long-day adapted S. phureja for soft rot resistance in order to identify parents which will allow the rapid introduction of resistance into commercially acceptable tetraploid material. In the case of dry rot, long-day adapted Neotuberosum clones derived from andigena were examined. The assessment of a sample of SCRI elite Neotuberosum clones for new sources of resistance to F.c. and F.s., and of progenies derived from crossing selected clones to a range of Tuberosum cultivars and breeding lines is described.
Materials and methods
One hundred and thirteen clones (84 Neotuberosum and 29 hybrids) were assessed for dry-rot resistance. Inoculum of F.s. and F.c. was prepared in sand-cornmeal medium incubated for 4 weeks at room temperature. Tubers were inoculated with either F.c. or F.s., incubated at 85-90% RH at 10oC for 45 days and the resulting lesion measured. A crossing programme was carried out in 1994/5 comprising eight Neotuberosum parents chosen for their resistance to F.c. and/or F.s. and for putative resistance to late blight. The other set of parents comprised eight new cultivars from SCRI and two clones with good blight and PCN resistance1 respectively. A dry rot progeny test was carried out on 2 replicates of each of the resulting 72 progenies using the above inoculation method.
Results and conclusions
Neotuberosum clones with differing levels of resistance to F.c. and F.s. were selected and used in crosses with tuberosum clones. Assessment of the resulting progenies showed that there was little correlation between disease scores for the two Fusarium species, indicating that resistance to each species is distinct. It is concluded that there are good prospects for combining resistance to the two Fusarium species from different sources and also for achieving high levels of other desirable characteristics.