Physiological Basis Of Awn Length Variation In Elymus Nutans And Effects Of Awn On Seed Yield

Elymus nutans is an excellent forage of the genus Elymus in the Gramineae family.It has excellent characteristics such as wide adaptability,good palatability and strong cold resistance.It plays an important role in the ecological restoration and the development of grassland and animal husbandry in the Qinghai-Tibet Plateau.Although the wild E.nutans germplasm resources in China are very rich,the lack of varieties seriously restricts its large-scale promotion and utilization.Awns are considered as important structure of many gramineous crops’ panicles,and have attracted much attention due to their positive role in seed propagation,photosynthesis,transpiration and yield.E.nutans germplasm resources have rich variations in awns.However,the anatomical structure,physiological and biochemical characteristics of its awn during development,as well as its impact on other seed related traits,are still unclear.In this study,E.nutans germplasm resources from different geographical sources were selected as the research object,analyzed the awns length phenotype and genetic variation,studied the morphological structure,development dynamics,physiological and biochemical mechanism of awns,and explored the effect of awns on seed yield and germination characteristics.The research results are of great significance to the breeding of high yield varieties of E.nutans and the related research on the grass awns.The main results are as follows:1.To reveal the phenotypic variation of awn length and its relationship with seed related traits in E.nutans germplasm resources from different sources.Taking 200 individual plants from 40 materials as the research object,7 agronomic characters such as awn length,awn shape type and 1000-grain weight were evaluated.The results showed that there were different degrees of variation in each character,and the variation coefficient of awn shape type was the largest,23.44%;The Shannon-Weaver diversity index is also the highest,at 2.17.The cluster results gathered the germplasm with similar awn length and awn shape types of the tested materials.The results of principal component analysis showed that the eigenvalues of the first three principal components could explain 83.63% of the total variation,and the morphological characters of lemma length,1000-grain weight and awn length had higher eigenvector values.These morphological indexes could basically reveal the morphological variation of the tested E.nutans germplasm resources.2.To reveal the anatomical structure and physiological mechanisms of awns in different developmental stages of E.nutans.Three E.nutans germplasm with different awn length were selected to analyze the anatomical structure,enzyme and hormone characteristics of awns at booting,heading,flowering and maturity stage.The results showed that the cross section of E.nutans awn was sharp triangle,similar to the structure of wheat awn.In general,long awns grows faster than short awns from booting stage to heading stage,but there is no significant difference in awn length at heading stage,flowering stage and maturity stage.There was no significant difference in the size of protruding thorns and stomas on the outer surface of awns in the three stages,but in the four stages of development,the number of stomas of long awns was more than that of short awns.Among the 12 hormone and enzyme indexes measured,the contents of cytokinin(CTK),abscisic acid(ABA)and ethylene(ETH)and the activities of superoxide dismutase(SOD)and peroxidase(POD)were significantly related to the development of awn.The study revealed the anatomical and physiological characteristics of awn development of E.nutans,which will provide a research basis for further study of its awn function and molecular mechanism of awn development.3.To reveal the effect of awning on seed related traits of E.nutans,this experiment used 10 E.nutans germplasm as materials to study the effect of awning removal on seed yield and germination characteristics.In general,under the two growth conditions,the awning treatment led to a significant reduction in the 1000-grain weight of seeds and seed yield per plant(P<0.05).Compared with awned plants,awnless plants may have higher BTS value and higher seeds per inflorescence,but the 1000-grain weight of seeds is reduced,which is greater than the increase of seed number,so the seed yield per plant is lower.There was a significant negative correlation between awn length and germination rate and germination index(P<0.05).In addition,this study also found that there was a negative interaction between the measured seed traits and seed germination.