Preliminary Study On The Division Of Heterosis Groups In Soybean

Soybean is rich in protein and vegetable oil.It contains many phytochemicals,such as isoflavones and phenolic compounds.Because of its nutritional value,soybean is considered as a traditional health food,so people's demand for soybean is increasing.But as the source of soybean,soybean production in China once ranked first in the world,and was surpassed by the United States,Brazil,Argentina and other countries.From a net soybean exporter to the world's largest soybean importer.By 2018,China's soybean output was 15.28 million tons,and its import volume was 82.31 million tons.The self-sufficiency rate of soybean was about 15%.The reason for this phenomenon lies in the continuous reduction of cultivated land area and the low yield of soybean.There is a wide gap between production and demand.This situation of soybean can not be self-sufficient urgently requires the upgrading of soybean breeding technology.After years of breeding practice,it was concluded that the utilization of heterosis was an effective way to improve soybean yield per unit area.However,due to the blindness of parents selection,there are more than 300 sterile lines and 400 restorer lines,and more than 600combinations are made every year,while only 12 hybrids are bred,so the research efficiency is very low.Therefore,using the breeding experience of maize,rice and other crops for reference,the heterosis groups were divided by a series of methods to provide direction for parent selection of soybean and promote the industrialization process of hybrid soybean.At the same time,the division of heterosis groups will be helpful to guide conventional breeding.This study used 5 cytoplasmic male sterile lines of soybean as female parent and 12restorer lines as male parent,and adopted NCII design method to compose 60 hybrid combinations to carry out heterosis,combining ability effect,and number of seeds per pod,respectively,for yield,pods per plant,seeds per pod and seeds per pod.Based on the correlation analysis with F1 traits and SRAP molecular markers,17 soybean parents were divided into heterosis groups.The following conclusions were drawn:1.It is basically clear that soybean heterosis is ubiquitous in F₁,but there are great differences among different combinations.The middle parent dominant combination accounted for 55%of all F1 yield traits,the super high parent dominant combination accounted for 30%,and the middle and super high parent dominant combination accounted for 20%of all F1 yield traits.The middle parent dominant combinations of yield-related traits such as pod number per plant,seed number per plant and seed number per pod accounted for 55%,56.67%and 23.33%respectively.It was found that domestic and foreign varieties had strong heterosis.2.The average mid-parent dominance of yield,number of pods per plant and number of grains per plant in the four agronomic traits investigated was positive,but only the mid-parent dominance of number of grains per pod was negative.It shows that the yield-related traits are interrelated and mutually restrictive.At the same time,the analysis of Heterosis of yield-related traits showed that the Heterosis of pod number per plant and grain number per plant was generally high in combinations with high yield heterosis,and the Heterosis of grain number per pod was negative,indicating that pod number per plant and grain number per plant contributed more to yield.3.Combining ability analysis showed that the general combining ability?GCA?of 17parents ranged from-27.94%to 56.62%,and six of them showed positive effects.The special combining ability?SCA?of 30 hybrid combinations was positive,accounting for 50%of the total.From the analysis of yield heterosis and combining ability effect,it is concluded that the parents or one of the parents of high heterosis combination have higher general combining ability and positive special combining ability.4.Through the correlation analysis of different traits heterosis,combining ability and F₁character value,SCA was correlated with F1 grain yield,heterosis and character value of pod number per plant;GCA was significantly correlated with yield character value and mid-parent advantage of grain number per plant;and was significantly correlated with mid-parent advantage of pod number per plant,super-parent advantage and character value of pod number per plant;SCA and GCA were not correlated with any character.relevant.5.The results of heterosis group division:17 parents were divided into 7 groups by traits value,combining ability and genetic distance.Combining the results of yield analysis,heterosis and three classification methods,it was found that heterosis combinations generally came from different groups.