Phenotypic Diversity And Seed Shattering Mechanism Of Elymus Sibiricus Germplasm Resources

Elymus sibiricus is a perennial herb of Gramineae,because of its high nutritional quality and good palatability,it is widely used as an excellent forage grass and plays an important role in grassland animal husbandry production.Seed shattering is a common phenomenon in grasses,and the seed shattering of Elymus sibiricus is also more serious.For wild germplasm,seed shattering is conducive to the expansion and reproduction of the population,but for cultivated varieties.this character makes Elymus not only not conducive to field management,but also not conducive to mechanical harvesting,which is also one of the important reasons why its seed yield is lower than the actual seed yield.seed shattering has also become an important character in urgent need of domestication and improvement in the process of Elymus sibiricus breeding.In this paper,23 phenotypic characters of 39 Elymus sibiricus germplasm from 7 different distribution areas,such as Xinjiang and Qinghai,were analyzed by multivariate statistical analysis,and the shattering rate was determined to screen the differential germplasm.The seed shattering mechanism of Elymus sibiricus was studied by the changes of cell wall hydrolase activity and endogenous hormone content in the abscission zone.The main results of this paper are as follows:(1)The genetic variation of phenotypic characters of Elymus sibiricus germplasm is rich,and the coefficient of variation of 23 phenotypic characters ranges from 8.53%to 41.52%.Among them,the genetic variation of ear and leaf ch aracters is the largest,and the broad heritability of 1000-grain weight and spikelet width are 72.55%and 59.57%,respectively.Correlation analysis showed that flag leaf length,width,inverted second leaf length and width were significantly positively correlated with inflorescence length,ear length,spikelet number and seed length,while floret number was negatively correlated with 1000-grain weight.39 materials were classified into 5 groups by cluster analysis based on phenotypic characters.Through principal component analysis,the cumulative contribution rate of the first six principal components reached 78.29%.(2)The highest shattering rate of Elymus sibiricus is between 40%and 45%at maturity.The grain drop rate was positively correlated with flag leaf length,inverted 2 leaf length,stem node number,seed awn length and seed length,and negatively correlated with ear leaf distance,first internode length under ear and first Internode length of ear axis.The shattering rate of L40 and L12 is relatively low,which is 34.13%and 37.51%.The shattering rate of L26 and L29 is higher,which is 52.62%and 53.91%.(3)On the 35th day after heading,the cellulase activity and polygalacturonase activity in the abscission zone of high deciduous germplasm were significantly higher than those of low deciduous germplasm,and the abscisic acid content in abscission zone of high deciduous germplasm was also higher than that of low deciduous germplasm.On the contrary,the auxin content in the abscission zone of high deciduous germplasm was significantly lower than that of low deciduous germplasm.The ABA/IAA content of 4 germplasms was positively correlated with polygalacturonase and cellulase activity.The above results showed that leaf length,glume size,spikelet length and width,stem length,seed length and seed width were the main factors leading to the phenotypic difference of Elymus sibiricus,while the level of hormone was the key factor leading to the difference of seed drop of Elymus sibiricus.