Selection During Early Generations And Evaluation At Late Generation Of Low-phytic-acid Soybean Lines

The trace metal elements can be chelated by phytic acid,which is difficult to be absorbed and utilized by monogastric animals.At the same time,phytic acid discharged into wastewater has caused water eutrophication.To develop soybean varieties with low phytic acid is the most economical and effective way to solve this problem.In this study,CX1834-1-2,progenies of soybean low phytic acid mutant,was used as a donor of low phytic acid,which was crossed with several high-yielding soybean varieties（Cangdou10,Lu97013,K117-3,Pudou1802,etc.）to produce segregation populations in different generations.Therein,the progenies at the early generations were suffered selection for two continuous generations by three means of slight-damaged single seed screening,SSR marker-assistant selection at the seedling stage and plant selection at maturity stage in field,respectively;the advanced low-phytic-acid lines were evaluated on the base of agronomic,yield and seed-quality traits.The results are as follows:（1）The selected soybean seeds with slight damage can germinate successfully,and grown well as the normal control;（2）During the early generations（F₂-F₄）of soybean breeding,the combining of single seed screening for phytic acid content and marker-assistant selection can identify the target plants with low-phytic-acid trait（double recessive homozygotes）as soon as possible.After double selection,the proportion of low-phytic-acid individuals was increased effectively in the subsequent generations.（3）The effective selection strategy to develop low-phytic-acid soybeans can be proposed as follows:in the F₁ generation,the plants should be cultivated well to produce seed as many as possible,meanwhile,to identify true hybrids derived from the crosses between the adaptive high-yielding parent and low-phytic-acid donor（CX1834-1-2）according to phenotypes（such as color of flower and pubescence,leaf shape,etc.）or polymorphic identification with SSR markers.In F₂generation,single seed screening with slight-damage was conducted firstly,and the selected low-phytic-acid seeds were sown in field.After seedling emergence,leaf DNA was extracted for SSR marker-assisted selection,and the homozygotes or heterozygotes consistent to low-phytic-acid donor parent were marked in the field.Obviously undesirable plants should be dropped.In F₃ generation,the selection procedure was repeated as before,however,the recessive homozygous plants were retained.In the subsequent generations,selection target of the offspring was transfer to yield components and agronomic traits,selecting elite plants or lines,until genetic stable line was achieved.（4）The correlation analysis of 11 traits of stable lines indicated that,for the point of Pearson’s correlation coefficient,phytic acid content was negative correlation with soluble protein content of soybean seed only（P<0.05）,but not with other agronomic,yield and seed quality traits.However,partial correlation analysis showed that there was no correlation between phytic acid content and the tested 10 indexes.Simple correlation reflects only a superficial correlation,but the inner correlation between traits should be determined by partial correlation analysis.Therefore,the introduction of low phytic acid traits will not significantly affect the detected traits,and it is possible to development low-phytic-acid varieties with excellent comprehensive traits.（5）Five low-phytic-acid soybean lines,with phytic acid content less than 10.18g/kg,were identified from 29 stable lines of phytic acid breeding program by means of the Grey Correlation Analysis.The determined lines of 21B3468 and 21B3471 have achieved the breeding goals of high yield,high quality and low phytic acid,and their utilization should be further identified in future.In conclusion,the effective selection strategy to develop low-phytic-acid soybeans proposed in this study can be refer to soybean breeders.The established segregation populations can be used to develop new soybean varieties with high yield and low phytic acid.The selected stable varieties characterized as high yield and high quality and low phytic acid will be involved in formal regional soybean test and to identify their utility.