Karwasra, S.S.Sharma, Vipin Kumar2016-10-132016-10-132016http://krishikosh.egranth.ac.in/handle/1/80502Powdery mildew disease caused by Erysiphe graminis f. sp. tritici is an important disease of wheat ( Triticum aestivum L.) in the north eastern region of Haryana and adjoining areas of states of Punjab and Himachal Pradesh. Studies on epidemiology and management of this disease were carried out at IIWBR, Karnal and Regional Research Station, Dhaulakuan duing rabi 2012-13 and 2013-14. Disease first appeared in hilly areas of Dhaulakuan at ear heading stage during the first week of February followed by Gurdaspur and plains of Yamunanagar at anthesis stage during the second week of February and spread to Ambala, Ludhiana, Kar nal and Kaul at anthesis, post anthesis and grain formation stage, respectively. Out of 203 entries evaluated, 37 were found resistant at both the locations. Two varieties viz., DPW 621-50 and PBW 550 while, six varieties viz., WHD 896, WHD 942, WHD 943, W HD 948 and PWD 233 showed slow mildewing behaviour at Karnal and Dhaulakuan, respectively. Increased minimum temperature and evening relative humidity collectively explained disease progression from 45 to 84 per cent at both the locations as the disease was favoured by mean temperature of 21.0 to 21.4°C at Karnal and 18.3 to 21.0°C at Dhaulakuan. Maximum, minimum temperature and evening relative humidity collectively explained disease progression from 73 to 84 per cent at both the locations. Physiological and biochemical analysis in healthy and infected leaves of resistant (DDK 1029) and susceptible (PBW 343) varieties revealed non-significant effect on total chlorophyll content in infected leaves as compared to healthy leaves of resistant variety. In suscep tible variety, stomatal conductance in diseased leaves decreased at initial stage of infection and then reduced at higher rate at all stages of disease. There was a gradual reduction in photosynthetic and transpiration rate at all the stages of infection i n both the varieties, but reduction was more in the leaves of susceptible. In susceptible variety, the reduction in photosynthetic rate was found to be less at initial stage of disease but reduced sharpl y at later stages. Total phenol contents were higher in healthy leaves of resistant variety and after infection, the total phenol content increased in resistant variety at initial stages of disease, while the decrease was less at later stage. In susceptib le variety the total phenol content continued to increase at all stages of infection. Total sugar and non reducing sugar content in both the varieties increased after infection but the increase was more in susceptible variety. Activity of PPO and POX was found to be increased in resistant variety at all the stages. In resistant variety, there was significant increase in PPO and POX activity at disease initiation thereafter slightly decreased at later stages. Among various fungicides tested, propiconazole 25% EC and tridemorph 40% SC were found most effective even at lower dose (0.05%) and controlled the disease up to 96.55 and 93.64 per cent, respectively, as compared to untreated control.enDiseases, Wheats, Biological phenomena, Planting, Fungi, Phenols, Enzymes, Crops, Developmental stages, FungicidesThesis