**Acknowledgements**

For the following 2014–2015 season, the tubers of 71 genotypes that were not damaged by late blight were harvested. The experiment was designed with three replicates in randomized blocks. We planted three plants of each genotype that hold R genes in front of three plants of

Rows of the susceptible Atlantic cultivar were also planted in the border and interspersed in the complete area of the assay. AUDPC values were calculated for all genotypes and susceptible control plots. A pairwise comparison was performed between each genotype and the respective control plot. We calculated the AUDPC from the visual estimation of the percent-

In the 2013–2014 season, an evaluation of randomly selected individual plants from the progeny of Ma*R8* and Ma*R9* crossed with the commercial varieties indicated that progeny carrying the *R2* gene had less foliage damage represented by lower AUDPC values. Furthermore, higher AUDPC values were found in plants that did not contain R genes. We were not able to

In the second season, we utilized undamaged plants from the first season. Most of the plants carrying R genes again had lower AUDPC values than the control plots. Interestingly, plants carrying the *R3* gene did not have different AUDPC values compared to the susceptible con-

In conclusion, we found that plants carrying R genes were only slightly affected by late blight in conditions of high pathogenic pressure, with the exception of the *R3a* and *R3b* genes (**Table 5**). Out of the 11 genotypes that did not show differences compared to the susceptible control, nine were holders of genes *R3a* and *R3b,* suggesting that these R genes are less resistant to late blight

**Table 5.** Genotypes harboring different numbers of R genes and % showing an AUDPC value significantly lower than

**% genotypes significantly different to** 

**susceptible**

**Number of genotypes** 

and, therefore, should not be used in breeding programs in Chile.

Genotypes carrying 1 R genes 5 60 Genotypes carrying 2 R genes 21 71 Genotypes carrying 3 R genes 18 94 Genotypes carrying 4 R genes 13 92 Any genotype carrying R1 27 96 Any genotype carrying R2 17 88 Genotypes carrying only R3a or R3b 20 55

**tested**

perform statistical analysis as there were different numbers of clones holding R genes.

the susceptible Atlantic cultivar (susceptible control) per each replicate.

age of infected foliage.

14 Potato - From Incas to All Over the World

**5.3. Results**

trol plots.

the susceptible control plots.

Financial support: Subsecretary of the Chilean Ministry of Agriculture through Potato Breeding Program project and Conservation of Genetic Resources program (501453-70). CORFO (Corporación de Fomento a la Producción) through INNOVA-Public Goods 14BPC4-28525.
