6.150
EPIDEMIOLOGY OF DOWNY MILDEW OF FENUGREEK
EPIDEMIOLOGY OF DOWNY MILDEW OF FENUGREEK G.S. SAHARAN and SOM PRAKASH Department of Plant Pathology CCS Haryana Agricultural University, Hisar-125 004, India Background and Objectives Fenugreek Trigonella foenum - graecum L. locally known as methi has got tremen-dous importance in the life of human beings as a food, fodder and medicine. Downy mildew caused by Peronospora frigonella Gaumann is the most widespread and devastating causing heavy yield losses all over India. The objectives of the present study is to determine the most congenial weather factors which influence disease development under field conditions. Materials and Methods The effect of environmental factors on the periodical and cumulative progression of downy mildew of fenugreek during 1993-94 and 1994-95 was measured at an interval of 3 days on cv. Hisar Sonali. The progress of disease was recorded in terms of increase in size (mm) and number of colonies. The environmental variables taken into account were max-imum temperature (Tmax 0C), minimum temperature Tmin C), relative humidity morning I(RHM %), relative humidity evening (RHE %), sunshine hours and rainfall (mm). Results and Conclusion The step-wise multiple regression analysis of all the six test independent variables indivisually and in all possible combinations that fit analysis best revealed that each factor played an important role in disease development. The cumulative increase In size of downy mildew colonies in relation to weather variables indicated that except sunshine hours all the factors played an important role in disease progress under field conditions. Data recorded during 1993-94 showed that when Tmax and RHE were taken together, R2 value was 0.59, however, with the addition of RHM, the R2 value increased to 0.83. Further with the introduction of Tmin the R2 value increased to 0.87. When Tmax, Tmln, RHM, RHE and RF were taken together, highest R2 value (0.90) was recorded. The maximum cumulative progression of colony size (0.29 mm) was recorded with 18.570C Tmax, 5.23 0C Tmin, 97.0 per cent RHM, 52.33 per cent RHE and 5.3 hours 55 prevailing during 18.1.1994 to 20.1.1994. The periodical progression of downy mildew number of colonies during 1993-94 and 1994-95 recorded that all the six independent variables showed more than 94 and 70 per cent variation in disease progression, respectively. Prediction equation during 1993-94 recorded that Tmax showed 0.70 R2 value. When RHE was introduced in the equation, the R2 value increased to 76 per cent. Likewise, the addition of further variables in the equations when Tmax and RHE have already been included showed further increase in R2 value. The maximum 94 per cent variation in disease progression was achieved when all the variables were taken together, however, slight decrease in R2 value (0.93) was recorded when the variable 55 was not added to the above equation. The progression of downy mildew of fenugreek measured in terms of size and number of colonies was faster and accounted for upto 90 per cent during 1994-95 crop season. There is no information on the epidemiology of downy mildew disease of fenugreek (1]. References 1. Som Prakash. 1997. Studies on epidemiology and control of.downy mildew and powdery mildew of fenugreek. Ph.D. Dissertation. CCS Haryana Agricultural University, Hisar, India, pp 171.