Effect of drought stress in the field and the relationship between an in vitro method (polyethylene glycol 6000) for screening sugar beet genetic resources.

This study was done in order to determine the relation of traits from laboratory tests with those of on farm tests to identify the most appropriate traits for screening sugar beet genotypes. Tests compared laboratory induced stress conditions to those on farm. 15 O-Type had 5 genotypes (control) classified as tolerant, one semi-tolerant and one sensitive. Tests were done in laboratory and on farm conditions. Plant drought stress was tested under severe drought conditions in a randomized complete block design with 6 replications at the research farm located in Karaj in 2008. Poly ethylene glycol 6000 was used in the laboratory tests as the solid medium to create various levels of water stress. Four water stress levels, at variations in osmosis potential of 0, 0.6, -0.7 and -0.8 MPa and twenty sugar beet genotypes were arranged as a factorial experiment on CRD with three replications under a controlled environment. Correlation of traits of these laboratory and on farm tests showed that in the stress condition of -0.6 MPa, the correlation of laboratory traits of wet weight of root had a positive and significant correlation in terms of p value at the level of one percent with evaluations of traits from on farm tests for root yield, sugar and white sugar, dry weight of root and proportion of dry weight of root to shoot. Under the stress condition of -0.8 MPa in the laboratory tests, wet weight of root showed a positive and significant correlation with the traits of root yield, sugar and white sugar and total dry weight of root and shoot (P<0.05). In general, the positive and significant correlation between root wet weight of sugar beet plantlet in laboratory condition with those traits from on farm tests can be used to determine water stress of about -0.6 MPa in the laboratory instead of water stress on farm for genotypes tolerant to drought and from root wet weight of genotypes having high yield of root, they can be sifted under intense water stress at farm.