DETERMINTION THE GENETIC RESISTANCE OF CERCOSPORA LEAF SPOT DISEASE in SOME SUGAR BEET CULTIVARS USING AGRONOMIC TRAITS AND MOLECULAR MARKERS by START CODON TARGETED (SCoTs)

ABSTRACT
Sugar beet (Beta vulgaris subsp. vulgaris) is root crop grown commercially for produce over 100 million tons per year of sugar (mainly sucrose) for worldwide consumption. Cercospora leaf spot is a foliar disease that caused by the fungus Cercospora beticola Sacc. can destroys the sugar beet yield. To identifying sugar beet cultivars with remarkable yield and disease resistance; six cultivars of sugar beet, namely Gergoria-KWS, BTS 2860, LP17B4011, MK 4199 (Emperator), Pintea, and Zeppelin were obtained. These six sugar beet cultivars were grown in experimental farm, Sakha Agriculture Research Station, Agriculture Research Center  and examined under field growth conditions for two successive seasons, 2019/2020 and 2020/202. Disease severity percentage, root and foliage-associated traits, % of sugar and total soluble solids (% TSS) content were measured. Novel start codon targeted (SCoT) markers via PCR-based applications using ten SCoT-specific primers was used and genetic similarity among cultivars were estimated. The results divided the studied cultivars to three classes; the first contains; Gerogoria-KWS and BTS2860 cultivars appear to have the lowest % disease severity (1.00-2.67 % and 0.83-5 %, respectively) and they have longer roots, higher biomass for foliage and root (on fresh and dry weight basis), higher content of TSS % and sucrose in the both seasons. The second class contains; Pintea, MK 4199 (Emperator), and LP17B4011 cultivars exhibited the highest % of disease severity, the lowest biomass and shortest roots.  The third class include, Zepplen cultivar had moderate of % disease severity and low TSS % content. In addition, the results of SCoT markers were showed that the average of Polymorphism percentage was 46.37 and obtain 54 polymorphic bands; there were two bands from them with molecular weight 1056 bp and 1100 bp generated via SCoT3 and SCoT4 analysis, in respectively were distinguished as associations to Gergoria and BTS2860, which could be attributed to the high disease resistance phenotypes in those two cultivars and absent in the rest sensitive cultivars. The obtained values of genetic similarity ranging from 0.76 to 0.92, by which the highest was between Gerogoria and BTS2860 cultivars. Moreover, cluster analysis was conducted based on the genetic relationships illustrated a high degree of harmony between growth traits and results of PCR-based SCoT analysis. These results indicate the efficiency of SCoT markers in distinguish among the cultivars for the resistance or the sensitivity to this disease.