Susceptibility assessment and genetic population structure associated with Rhizoctonia solani AG3-PT - Potato stem canker disease

Rhizoctonia solani Kühn AG3-PT causes stem canker (SCD), and significantly impacts potato, Solanum tuberosum L. production globally. However, up to date, there are few resistant or tolerant potato cultivars to R. solani. Given the importance of the subject, we screened ninety-two potato genotypes to SCD, R. solani in the field and greenhouse conditions. Of which, fifty genotypes were subjected to genetic diversity analyzing using 20 Inter Simple Sequence Repeats (ISSR) primers. SCD severity on genotypes ranged from 5 to 73% in the field, and out of 20 used ISSR primer pairs, 14 primers generated 485 loci, of which 216 (45%) showed polymorphic bands. The highest percentage (67%) of polymorphisms was in uBC834 primer. Polymorphism information content value varied from 0.262 to 0.459 with an average of 0.338. Nei's measure of average population genetic diversity per locus ranged from 0.06 to 0.5. Effective number of alleles, Nei's genetic diversity and Shannon's Information Index were 1.530, 0.266, and 0.392, respectively. uBC834 and uBC811 primers identified the most polymorphic loci. According to simple-matching coefficient, the highest similarity (99%) was among “KSG64”, “KSG82”, ‏“KSG81”, ‏“KSG21”, “KSG31”, and “KSG109”, and lowest similarity (54%) in “8708/177” and “KSG300”. Thus, resistant sources can play a significant role in disease management in an integrated pest management planning program. Moreover, diverse potato resistant/susceptible genotypes reported in this study will be useful to generate mapping populations for potato and work in breeding programs for developing and releasing new resistant cultivars for SCD, R. solani infection.