Drought stress induced in barley cultivars (Hordeurn vulgare L.) by polyethylene glycol, probed by germination, root length and chlorophyll a fluorescence rise (OJIP)

Seed germination and seedling establishment of six varieties of barley plants (Hordeum vulgare L.) were tested for drought tolerance using polyethylene glycol-6000 solutions (PEG) with different osmotic potentials (0 MPa, -0.5 MPa, -1 MPa, -1.5 MPa and -2 MPa). Seeds of three varieties obtained from the National Institute of Agricultural Research (INRA) of Morocco and three landrace populations collected at three localities in the south of Morocco were used in the present study. In addition, seed germination, emergence and root length were measured. The performance index (PI) and the maximum quantum yield of primary photochemistry (phi(Po)) extracted from the polyphasic fluorescence transient (OJIP) were used to evaluate drought tolerance. The sensitivity to the osmotic stress of all measured parameters was cultivar dependent. The different varieties showed a gradual decrease in the performance index (PI), it varied between 86% and 73% of the control under severe osmotic stress (-2 MPa). Therefore, the osmotic stress has little effect on the maximum quantum yield of photosystem II (phi(Po) = F-V/F-M,). The studied varieties can be split into three groups that varied in the reduction of their PI at low and high osmotic stress. We show that a positive correlation exist between change in performance index and root length measured after the different PEG-6000 treatments. These results suggest that chlorophyll a fluorescence, and especially the performance index, could be used for the screening of barley varieties for drought tolerance.