Hossein Sabet Zangeneh - Ph.D. Student of weed science, Department of Agronomy and Plant breeding, Faculty of Agriculture, University of Mohaghegh Ardabili, Ardabil, Iran.
Hamid Reza Mohammaddust Chamanabad - Associate Prof. Department of Agronomy and Plant breeding, Faculty of Agriculture, university of Mohaghegh Ardabili, Ardabil, Iran.
Eskander Zand - Professor. Weed Research Institute of Plant Protection,Tehran, Iran.
Ali Asgheri - Associate Prof. Department of Agronomy and Plant breeding, Faculty of Agriculture, university of Mohaghegh Ardabili, Ardabil, Iran.

Laboratory studies were conducted to compare the relative fitness of clodinafop-propargyl herbicide resistant Lolium rigidum accessions with their clodinafop-propargyl susceptible counterparts in 2014. Factors evaluated were Lolium populations at constant salinity stress (0, 5, 10, 15, 20 and 25 dS cm2) and water stress (0, -3, -6, -9, -12 and -15 bar). The maximum germination in salinity stress was among three biotypes regarding susceptible biotype with 93.62 percent. The concentration of salinity which 50% seeds germination reached S and Semi-R biotypes to the is more than Rbiotype. In salinity stress the highest rate of germination in the S biotype of 8.66 (number of germinated seeds in days) at a concentration of 17 dS RG reaches 50% in S and Semi-R biotypes and in R biotypes in salinity 14 dS cm2. The results of the application of various potential water showed that the more negative water potential, germination all biotypes (R, Semi-R and S) dropped and in potential -15 bar PG in R and Semi-R biotypes to less than 15 percent. Coefficients from the regression equation sigmoid three parameter to data PG resistant and susceptible biotypes showed that Semi-R biotype Compared to R and S were more tolerant of water stress and in water potential 7.5, it PG Reduced to 50 percent. In examining the relative fitness of ryegrass biotypes water and salinity stress showed that Semi-R and R biotypes the cost of considerable fitness, But the most results cost fitness no significant. © 2016 Published by CASRP publishing company Ltd. UK. Selection and/or peer-review under responsibility of Center of Advanced Scientific Research and Publications Ltd. UK.

Biotype, Fitness, Lolium rigidum, Salinity stress, Water stress