Screening Of Low-P Tolerant Landraces And Its Physiological Mechanism Of Soybean

To study the tolerance of soybean (Glycine max) genotypes to low phosphorus stress, 97 landraces from Hebei growing-areas were studied under two phosphorus levels with the method of vermiculite and solution culturing. Relative values were investigated about total biomass, biomass of roots, biomass of shoots, P contents of roots, P contents of shoots, P contents of whole plant and root-shoot ratio. The index of plant phosphorus efficiency was suggested as reliable screening character to low-P stress, and all landraces were classified into three groups based on this index. In addition, the morphological and physiological characteristics of different soybean genotypes were also studied. The results were summarized as following.(1) Significant differences were found in six characteristics, i.e. the total biomass, biomass of roots, biomass of shoots, P contents of roots, P contents of shoots and P contents of whole plant, except for the root-shoot ratio.(2) The correlation analysis and stepwise regression analysis (partial correlation analysis) indicated that the relative value of total biomass and relative value of total P contents were significantly related to the others. The best regression equations that was Y=2.257+2.732X₁-1.737X₆-3.556X₇(F=24.78^**,R=0.645)suggested total biomass and total P contents were key indexes. The ratio of the two relative values, i.e. the index of plant phosphorus efficiency, was suggested as reliable screening character to low phosphorus stress.(3) Based on the index of plant phosphorus efficiency, 97 soybean landraces were classified into three groups. Groupâ… included twelve low-P tolerant landraces, and the variety"Pihuli"and"Bendihei"were selected for its higher tolerance. Groupâ…¢were low-P sensitive varieties (i.e."bailumang"and"suningxiaoheidou") and groupâ…¡including sixty-four were the middle types.(4) Under the stress of low-P, the characters of morphological and physiological were affected such as the contents of MDA, the activation of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), acid phosphatase activity (APA), root length and root surface areas. Futher analysis showed that the activities of protective enzymes (SOD, POD, and APA) in low-P tolerant landraces increased higher than those low-P sensitive varieties. The root length and surface areas of low-P tolerant landraces were also increased more than those sensitive varieties.