Molecular Detection of R1 and R3a Alleles in Late Blight Differentials and Germplasms of Potato and It’s Implications

C.H. Li 1,2 , D.H. Hao 1 , S.H. Chen 2 A total of 161 potato germplasms including 15 Scottish R gene differentials, 65 advanced clones of breeding population B (partial resistance to Late blight), 55 genotypes of

Solanum verrucossum

and 26 common cultivars were detected for the presence of R1 and R3a alleles by using PCR amplification with corresponding specific primer pairs. The expected fragment of ~1400 bp size amplified from R1 locus was not only found in R1 and a combination of R1 with other major resistance factors, but also found in R5, R6 and R9 differentials, 18 advanced clones of population B, and 12 common cultivars, despite that these clones/cultivars could be subjected to be the susceptible or moderate/partial resistance clones/cultivars under local conditions. Partial sequencing results showed that the expected fragments obtained from cv. Atlantic, Kennebec and Cooperation 88, and late blight differentials of R1, R5, R6 and R1R2 shared 99.83% to 100% identity with the corresponding part of reported R1 gene (AF447489). With touchdown PCR method, we found that one or two expected fragment(s) of ~980 bp or/and ~1050 bp amplified from R3a locus could be obtained from almost all potato germplasms used in this experiments except that of 6 genotypes of

Solanum verrucossum.

Partial sequencing results of expected fragments from 10 randomly selected clones indicated that they shared over 95% identity with each other and were allelic versions of R3a locus. The above results confirmed that Scottish R gene differentials harbors other known major resistance gene(s) or their homologues besides that have been denominated, and implied that R3a allelic versions might widely distribute in potato germplasms. Additionally, it is also implicated that the presence of R1 gene and/or R3a allelic versions in a clone/cultivar were not sufficient to define it’s resistance type (e.g. susceptible or resistant to late blight). 1 Roots and Tubers Crop Research Institute, Yunnan Normal University, Kunming 650092, China 2 College of Life-Science, Yunnan University, Kunming 650031, China