Abstract

Potato early blight disease caused by Alternaria solani is one of the major factors limiting potato production worldwide. Developing highly resistant cultivars is the most effective way to control the disease. In this study, 20 random amplified polymorphic DNA (RAPD) and six simple sequence repeats (SSR) primers were applied to assess the genetic diversity and to identify molecular markers associated with resistance to early blight disease in resistant (Cara, Spunta and Valor), moderately resistant (Hermes and Atlantic) and susceptible (Atlas, Desiree and Lady-Rosetta) potato cultivars. The results showed that 296 and 29 clear fragments were amplified by RAPD and SSR, respectively. SSR revealed higher frequency of polymorphic bands (93.1%) than RAPD (57.4%). The clustering pattern obtained from the analyses of two marker systems showed a similar distribution of the tested potato cultivars. Interestingly, the resistant potato cultivars were grouped together in the dendrograms generated from RAPD and SSR clustering analyses. RAPD primers OPY-07, OPG-05, OPA-10 and OPA-18 generated five unique fragments (OPY-07_880bp, OPG-05_949bp, OPA-10_1000bp, OPA-18_2030bp and OPA-18_1128bp) presented only in resistant cultivars. In addition, all resistant cultivars and moderate resistant cultivar (Hermes) shared two markers; one RAPD (OPA-18_1070bp) and the other SSR (STI57_209bp). On the other hand, RAPD primer UBC-17 generated specific fragment UBC-17_720bp presented only in susceptible cultivars and moderate resistant cultivar (Atlantic). This study demonstrate that RAPD and SSR markers can be effectively used to assess the genetic variation among potato cultivars in order to develop molecular markers associated with early blight disease to improve potato breeding programs.

Key words: Alternaria solani, cluster analysis, resistance, Solanum tuberosum.