The Study On The Second Recurrent Selection For Low Coumarin Content And Detection Technology Of Near-infrared Model For Quality Trait In Melilotus

Melilotus is a widely cultivated legume forage with high feeding,medicinal value and strong adaptability.The main cultivated species in this genus are M.officinalis and M.albus in the world.Reducing the coumarin content in the Melilotus can effectively improve its feeding value.Since 2011,our group has introduced 101 Melilotus germplasm resources all over world and used to select excellent half sib families for genetic improvement.Our group evaluated the yield traits and coumarin of the half sib families and finished the first recurrent selection in 2014-2015.It is necessary to carry out several recurrent selections in order to breed stable new cultivars.In this study,the superior half sib families selected from the first recurrent selection by our team was used as materials to carry out the second recurrent selection.We establish a rapid prediction model for the quality traits and coumarin content of Melilotus using near-infrared spectroscopy.The main results are as follows:1.The second recurrent selection was completed on half sib families of Melilotus.The half sib families obtained from the first recurrent selection,including 25 of M.officinalis and 25 of M.albus,respectively,were evaluated on the traits of yield,quality and coumarin content in 2018-2019 at Yuzhong county and Linze county of Gansu Province,China.Analysis of variance,correlation analysis,principal component analysis and cluster analysis were used to conduct a comprehensive analysis.The results showed that there are significant genotypic variations(P<0.01)on the traits of plant height,dry weight,fiber,and coumarin content among half sib families and there are significant genotype by environment interactions(P<0.01)on the traits of dry weight,plant height,stem diameter.The genetic gain of dry weight and plant height predicted by genotypic variance was higher after the second recurrent selection.The coumarin was negatively correlated with dry weight,plant height,stem diameter and fiber,and positively correlated with crude protein.The dry weight,plant height and yield traits had significant or very significant correlation with the quality traits.Pattern analysis showed the relationship of agronomic traits by image,and summarized the comprehensive performance of half sib families.All half sib families in two Melilotus species were divided into four groups by cluster analysis.The second group was the best group of M.officinalis,which have highest average dry weight and plant height with 138.70g and 129.05cm,respectively.The average coumarin content was 0.44%,which was the lowest among the four groups.The fourth group had the best performance in all group of M.albus,with higher dry weight,crude protein and the lowest coumarin content.These materials with better performance will be used in the breeding of new Melilotus cultivar.2.The NIR prediction model on quality trais and coumarin content were established in Melilotus.A total of 225 inter breeding materials of Melilotus were collected at Yuzhong county and Linze county of Gansu Province,100 each of M.officinalis and M.albus for calibration set and 25 for validation set of the models.Combining the near-infrared spectra of the calibration materials and the chemical values,near infrared prediction models of crude protein(CP),acid detergent fiber(ADF),neutral detergent fiber(NDF),acid detergent lignin(ADL)and coumarin(Cou)were established by using the partial least squares(PLS)and other mathematical measurement methods.The results showed that the chemical values of 200 calibration samples were as follows:CP 7.97%-13.49%,ADF 19.23%-48.19%,NDF 433.11%-54.99%,ADL 3.52%-12.03%,Cou 0.13%-1.1%,which showed a wide distribution range of the traits and suitable conditions.The calibration determination coefficients(R~2)of CP,NDF,ADF,ADL and Cou were 0.88,0.90,0.89,0.78 and 0.87,respectively,and the prediction standard deviations(SEC)were 0.987,1.416,1.264,0.521 and 0.072,respectively.Further validation of external samples showed that the prediction models of Cou and NDF had better prediction effect,and the prediction effect of ADL model needed further optimization compared with other models.The results showed that near infrared spectroscopy technology had great application in Melilotus.It laid a foundation for rapidly determination of quality traits and coumarin content in Melilotus.