Effect of irrigation regimes at early growing stage on development of some fungal disease of potatoes

In order to study the effect of water stress on fungal diseases causing wilt of potato in first growth stage (before tuberization)and reaction of potato cultivars to the diseases and stress this research were done according to split plot in randomized block design with three replication in which main treatments were different potato cultivars(Agria ,Marfona ,Arinda) and submain treatments were different irrigation regims base on the amount of water evaporation from plate class A ,in five level contain of:150 ,125 ,100 ,75 ,50 mm evap.the research performed in Karaj field station during 2002-2003.water consumption in experimental plots were measured by parshal flom 5 and 4 inch. That is put at the first and end position entering and exiting row water respectively. In addition to some agronomy characters like date of flowering ,tuberization , form of plant,infection percent of plots to different wilting disease such as Fusarium ,Verticillium ,Colletotrichum and disease severity of Rhizoctonia canker were noted.after one month percent of infection to diseases were recorded again and area under disease progress curve (AUDPC) were measured.at the end of experiment yield of each treatments recorded in harvesting time.data of experiment were analysed with SAS software statistically in each year and at the second year combined analysis on data were done. The result showed that ,effect of year in the experiment were significant so data analysis were done in each year separately.the highest amount of disease infection ,AUDPC ,yield related to 50mm evap.with water consumption and lowest one relste to 150mm evap. with Water consumption in two years.Agria and Arinda had the most and least amount of infection to Fusarium ,Verticillium and AUDPC in each year respectively.despite results of Rhizoctonia canker index (RCI) of cultivars showed that Agria had the lowest and Marfona had the highest RCI .in two years of experiment the treatment 75mm evap. in Arinda with means of 1.69% ,0.63% and 125mm evap. in Marfona with means of 2.65%,1.66% had the lowest infection to Fusarium and Verticillium wilt diseases respectively and their amount of AUDPC with means of 67.17 ,114.5 were the least among treatments in this research.