Evaluation of freezing temperature tolerance of lentil (Lens culinaris Medik) genotypes with using chlorophyll fluorescence parameters

During and after environmental stresses، measuring chlorophyll fluorescence parameters provide a fast and non-destructive method to evaluate the performance of photosynthetic system، and achieving data is used to determine the electron transfer rate and type of excited electrons quenching. So in order to assess tolerance of lentil genotypes including MLC7، MLC60، MLC185، MLC225، MLC357، Qazvin and Rabat to freezing temperatures consist of 0،-3،-6،-9،-12،-15،-18،-21،-24 oC، as a factorial experiment in randomized complete block design with three replications was conducted in the thermo gradient freezer. Reflection fluorescence of leaves adapted to low light (Fٰo)، maximum fluorescence of light adapted leaves (Fٰm)، variable fluorescence (Fٰv) and maximal photochemical efficiency potential PSII (Fٰv/Fٰm) were measured before، 5 and 10 days after the freezing treatments. Percent survival of different genotypes was determined also three weeks after applied the treatments. Analysis variance results showed that different genotypes were significantly varied related to chlorophyll fluorescence parameter in five days after the treatments. Two MLC225 and MLC7 genotypes indicated the highest and lowest F’o، respectively. MLC225، MLC357 and Qazvin genotypes allocated the highest values of Fٰm، also Rabat and MLC185 had the lowest levels. For Fٰv parameter، Rabat had the lowest contribution among the different lentil genotypes. Also in this phase، temperature levels regardless of similar F’o، had different Fٰv and Fٰv/Fٰm because of dissimilarity in F’m parameter، and relatively with decreased temperature this parameters were reduced. Three weeks after freezing treatment، MLC60 and Ghazvin genotypes had highest (49. 9%) and lowest (38. 3%) survival rate، respectively. Freezing effect on survival rate was significantly different. Survival rate decreased when freezing intensity was increased. Survival rate of plants were 56% in -12oC but in lower temperature none of plants of different genotypes could not be survive. There was positive correlation between survival rate and Fٰv/Fٰm ratio before freezing in all genotypes. While this correlation after freezing was weak. It seems we can predict freezing tolerance in lentil genotypes by measuring Fٰv/Fٰm ratio before exposure of freezing. Key words: L