Screen house experiment was carried out at Sakha Agricultural Research Station, Kafr El-Sheikh Governorate during 2007/2008 season to study the relation between fungicide and plant extract application on Cercospora beticola incidence and related characters as well as invertase enzyme on sugar beet. Two cultivars of sugar beet were selected; the two cultivars; Ras Poly and Fareda were used and planted in a split plot design. Topsin M70 (1 gm/liter) and plant extract Khella "Ammi visnaga" or pick-tooth (4000 ppm) were sued to control the disease. Artificial inoculation was done by using conidiospores suspension of Cercopora beticola. Inoculation was done 90 days after planting. Chemicals were applied three days before inoculation. Different traits were measured like, disease severity (%), root weight/plant, sugar percentage, sugar loss to molasses %, invertase enzyme activity, impurities in leaves and roots (Na + , K + and -amino-N), TSS %, chlorophyll content of leaves, purity (%), loss % for root and sugar. Seven readings to asses the disease incidence were taken. Disease severity (%) of cercospora leaf spot disease incidence was increased gradually especially for Ras Poly cv. than Fareda cv. under infected condition, but showed less values when treated with Topsin M70 followed by Khella. On the other hand, root weight, TSS%, sugar percentage, purity were highly affected than those under fungicide and plant extract treatments and loss percentages for root and sugar reached to maximum for Ras Poly than Fareda cv. Enzymatic activity of invertase reached the maximum under inoculation, while it was less when treated by Topsin M 70 and Khella plant extract. Na + and amino N increased by increasing disease severity (%), while K + behaved in different manner. Concerning reducing sugars in roots, recoverable sugar (%) and sugar loss to molasses increased by increasing disease severity (%), low values were obtained under fungicidal and plant extract treatment. Plant extract and resistant cvs, must be recommended to reduce the pollution either in water or in the soil of sugar beet plantations.

This investigation was conducted during 2011/2012 season at Sakha Agricultural Research Station farm and screen-house belongs to Sugar Crops Institute. This investigation was carried out on Kawamera sugar beet cultivar to answer the question of why young Leaves of sugar beet possess a high level of resistance to Cercospora leaf spot? Under artificial inoculation by Cercospora beticola spores (50 × 10 3 spores / ml), disease severity, chlorophyll content, losses in both yield and sugar were evaluated in randomized complete block design experiment. Different histological and biochemical factors were measured i.e., size of stomatal apparatus, mineral contents in different leaves starting from heart leaves up to outer leaves of the plant.Results obtained revealed that percent losses of inoculated leaves was 64.15 % in chlorophyll content, 52.05% and 41.74% in root and sugar yields were (respectively. Dimensions of stomatal apertures, diameter and stomata intensity showed that the young leaves were narrow and it has less number of stomata ranged from in inner leaves 115 stomata / mm 2 up to 331 stomata / mm 2 in outer leaves. Relative water content (RWC) was determined for sugar beet leaves, data obtained showed that young inner leaves contain less relative water content than mature outer leaves. Moreover, peroxidase activity was higher in the younger leaves than the mature one. Element analysis showed that N, P, Fe, Mn and Cu contents increased gradually from the inner first leaf and reduced in the outer fifth leaf, while the opposite was in potassium and zinc contents. Total phenol compounds were increased after inoculation; while the free and conjugated phenol compounds were higher in the young leaves than the oldest ones. This study clarified the role of leaf age and position in relation to resistance to Cercospora leaf spot disease.