EVALUATION OF RESISTANCE TO Cercospora LEAF SPOT DISEASE IN SOME LINES AND HYBRIDS OF SUGAR BEET UNDER NATURAL INFECTION IN KHUZESTAN PROVINCE

Nine monogerm lines and their 36 F1 hybrids were evaluated for their resistance to Cercospora leaf spot in a triple lattice design at Safiabad Agricultural Research Center, Dezful, Iran during 2008-2009 growing season. The plants of the experimental field were scored three times at approximately 30-day intervals. Scoring was accomplished by using 1-9 scale (KWS). The disease severity was determined by two methods, plot score and score of ten plants per plot, which in the second method, the average of ten plants score was considered as a plot score. Results obtained from each scoring method were independently analyzed. Results showed that RR607 genotype had the highest level of resistance to CLS. Hybrids derived from RR607 genotype: RR607×7112-36 and RR607×452 were more resistant to CLS than other hybrids. Based on yield traits in the presence of the disease 7173×474, 436×436-104, 436-104×SBFIROZ, 436-104×7173 and 436-104×452 hybrids were scored best in performance and resistance to CLS.