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R-gene Differentials for Late Blight Studies

Stuart Carnegie of the Scottish Agricultural Science Agency (SASA) will provide to anyone interested the R-gene differentials held by his institute.

Despite the development of numerous molecular marker systems for 'fingerprinting' isolates, there is still a strong desire to 'phenotype' the races to which isolates belong. To do this requires access to the R-gene differential series against which isolates are tested to determine which R-genes they can overcome. This series comprises two parts as follows:

1. Eleven genotypes, each expressing one of the eleven known (there are probably many others yet undiscovered) R-gene resistances from S. demissum, i.e. R1, R2, R3 or R11. Including the universal susceptible (or R0) gives twelve genotypes which are commonly referred to as the 'short' R-gene set; this set is essentially all that is required to type an isolate's race. Many 'short' sets around the world lack the R6 and/or R9 differentials, but these are included in this offer.

2. William Black also bred an additional series of differentials in which he combined the R1, R2, R3 and R4 resistances in all possible combinations. Thus there are six combinations expressing two resistances: R1.R2; R1.R3; R1.R4; R2.R3; R2.R4 and R3.R4; four combinations expressing three resistances: R1.R2.R3; R1.R2.R4; R1.R3.R4 and R2.R3.R4; and one combination with all four R1.R2.R3.R4. These additional genotypes in combination with the 'short' set make up the 'full' set of differentials.

All the differentials exist as pathogen-tested microplants at SASA and Stuart is willing to supply them as such around the world. SASA is the official body providing scientific support and services to government in Scotland, largely relating to agriculture. These responsibilities include plant health and SASA is home to the UK Potato Quarantine Unit. SASA is also responsible for the production and maintenance of seed potato nuclear stock (initial micropropagated planting material for seed production).

The best option for testing isolates for subsequent use in variety screening is the short set plus the genotype containing R1.2.3.4 genes.  This gives confidence that an isolate is capable of overcoming all 4 genes in combination if the reaction on a single R-gene differential was somewhat weak. Stuart is willing to supply five 'microprops' of each of the 12 genotypes in the 'short' set for £75 (Sterling) plus UK service tax of 17.5% (a total £88). Post and packaging are extra. This cost is the estimated actual cost to Stuart of generating new micropropagated plants with no margin whatsoever! Stuart recognizes that many of the parties requesting the set will have very little money, hence this exceptionally low charge.

A charge will also be made for the cost of transportation. Although more expensive, material will normally be sent by express carrier to minimize the risk of loss of plants in transit. However, the microprops are neither bulky nor heavy so the cost should not be large.

Additional R-gene differentials from the 'full' set can be ordered, also at a small charge; in this case probably ~ £ 8 (plus tax) per genotype. This price reflects our view that the major demand will be for the short set with only occasional requests for the others.

If you are interested, here is Stuart’s contact information:

Stuart Carnegie

Scottish Agricultural Science Agency

82 Craigs Road, East Craigs

Edinburgh EH 12 8NJ

Scotland, UK

Tel: (+44) 131 244 8858

Fax: (44) 131 244 8940

Email: Stuart.Carnegie(at)sasa.gsi.gov.uk

If you have any problems reaching Stuart, you can contact Jim Duncan and he will contact Stuart for you.

Jim Duncan

Scottish Crop Research Institute

Invergowrie, Dundee, DD2 5DA

Scotland, UK,

Tel: (+44) 1382 568518

Fax: (+44) 1382 568578

Email: j.duncan(at)scri.sari.ac.uk