Study On Genetic Variation Of Major Traits In The Hybrid Between M. Ruthenica ‘Zhilixing’ And Wild M. Ruthenica Sojak

Medicago ruthenica Sojak is a leguminous forage with strong resistance and adaptability,and rich genetic diversity.It exhibits significant variations in plant type,leaf and seed,making it an excellent genetic resource for genetic improvement of the Medicago and also has the potential to be selected and domesticated into cultivated forage.However,its low forage yield remains a major hindrance in its large-scale production and promotion.Therefore,in order to fully utilize the excellent characteristics of M.ruthenica germplasm resources and obtain new M.ruthenica germplasm with higher yield and richer genetic traits,two hybrid combinations were made by reciprocal crosses（ZH: ZB♀×HB♂;HZ: HB♀×ZB♂）,taking M.ruthenica ‘Zhilixing’（ZB）with good upright and high yield and wild M.ruthenica Sojak（HB）with strong stress resistance（yellow flower variant materials）as parents.By using SRAP molecular marker technology,hybrid identification was performed on the F₁ and F₂ generations of its two cross combinations,and further evaluation was conducted on its field agronomic traits and drought and cold resistance during seedling stage.The genetic variation patterns of the main traits were analyzed,and excellent variation materials were selected from them,laying the foundation for cultivating new germplasm of M.ruthenica with rich genetic traits and high stress resistance and yield.The main findings are as follows:（1）85 true hybrids were identified from 118 F₁ hybrid.Among them,all F₁ hybrids with HB as the female parent are true hybrids,while the combination with ZB as the female parent has a true hybrid acquisition rate of only 36.5%.This may be due to the low pollen vitality of HB or the high self-pollination rate of ZB.（2）The genetic variation coefficient of hybrid was high.Among them,the coefficient of variation of aboveground biomass per plant is the highest,followed by plant type index and stem leaf ratio,providing abundant genetic materials for further screening of superior offspring.（3）The hybrid offspring exhibited high polymorphism.Amplification of the F₁ generation with 18 pairs of SRAP primer combinations resulted in 150 polymorphic bands,with an average of 5.17 polymorphic bands amplified per primer pair and a percentage of polymorphic sites of 61.39%;Amplification of the F₂ generation with a combination of 19 SRAP primer pairs resulted in 178 polymorphic bands,with an average of 5.42 polymorphic bands amplified per primer pair and a percentage of polymorphic sites of 57.90%.（4）There were significant differences in heterosis of agronomic traits among the progeny of reciprocal cross of Medicago ruthenica.The F₁ generation of the combination with ZB as female parent had strong heterosis in leaf traits and yield per plant,with an average of 19.42% of mid-parent heterosis and 43.33% of negative over parent heterosis;The F₁ generation of the combination with HB as female parent showed no heterosis except for the number of primary branches,stem diameter,leaf width,plant type index and fresh dry ratio,and the heterosis intensity was weaker than that of the combination with ZB as female parent.In addition,the heterosis of F₂ was weaker than that of F₁.（5）In the F₂ hybrid,ZH1 is more drought-tolerant and HZ11 is more cold-tolerant,and both have better grass yield potential than their parents,making them excellent new germplasm for M.ruthenica.