| Dioscorea alata L.is an underground tuber crop.Because it is easy to cultivate and manage,its planting area is expanding,but its stem and leaf resources with large biomass have not been utilized.In order to turn the stem and leaf resources of Dioscorea alata L.into treasures,promote the virtuous circulation of resources and improve the comprehensive benefits of Dioscorea alata L.industry,21 cultivars of Dioscorea alata L.were selected in this study to determine the nutrients of stems and leaves and evaluate the feeding value,and the cultivars with the highest feeding value was selected to evaluate the quality of silage fermentation and optimize the silage conditions;the function of silage fermentation was evaluated by the methods of culture and uncultured.The main results are as follows:(1)The nutrient contents of 21 Dioscorea alata L.stems and leaves were dry matter 9.86%-1 7.53%,crude protein 16.26%-23.26%,crude fat 1.78%-4.1 9%,crude fiber 20.98%-30.98%,crude ash 7.60%-1 1.00%,acid detergent fiber 30.78%-39.I I%,neutral detergent fiber 44.32%-56.00%,nitrogen-free extract 37.20%-48.69%,tannin 0.49%-0.78%.It reveals that there are differences in nutritional components among different cultivars.The relative feed value(RFV)and grading index(G1)were used to evaluate the feeding quality of Dioscorea alata L.stems and leaves.The average RFV value was 115.20,which was in grade 2,and the average GI value was 3.37,which indicated that stems and leaves of Dioscorea alata L.have better feeding value.Among them,Cultivars Da128 and Da200 have the highest evaluation values,RFV was 134.03 and 128.08 respectively,which were all in Grade 1 standard,GI was 4.32 and 4.59 respectively,and they were in grade 2 and 2-3 standard,which indicated that they have the best feeding potential.(2)The silage products of stems and leaves of Dioscorea alata L.wcre graded according to sensory evaluation criteria(DLG),and the pH value and amount of lactic acid bacteria were determined.The optimum fermentation conditions were as follows:section length 2-3 cm,water content 65-70%,silage density 350 kg/m3-400 kg/m3.Eighteen strains of functional bacteria were isolated from silage fermentation broth and identified by 16S rRNA analysis.The results show that 10 strains have the highest similarity with Lactobacillusplantarum subsp.plantarum,which is regarded as the main functional bacteria.Six strains have the highest similarity with Lactobacillus pentosus,and the remaining two strains have the highest similarity with Lactobacillus brevis and Enterococcus casseliflavus,respectively.The strain WGX143 with the strongest acid-producing ability was screened as the experimental strain with subsequent silage additives.The optimum culture conditions of strain WGX143 were determined as follows:the optimum culture temp.erature was 37℃,the optimum culture pH was 6.0.the temperature was below 28℃.or above 40℃.and the initial pH was above 7.0.which would have an obvious negative inhibition effect on its growth.(3)After adding strain WGX1 43,the pH value of silage at all stages was significantly lower than that of control group,and the rate of decline of pH value in early stage was accelerated.The number of lactic acid bacteria in each stage of adding microbial agent was significantly higher than that in the control group,and the earlier stage was accelerated.High throughput sequencing was used to analyze the diversity of bacteria in silage fermentation.The results showed that there were 153 strains in the experimental group and the control group,and only 17 strains were different.However,the main functional bacteria.Lactobacillns plantarum subsp.plantarum,were at a high level in each stage of the experimental group,accounting for about 50%,while the control group accounted for a low proportion and grew slowly.This indicated that adding strain WGX143 could speed up the silage of ginseng potato stems and leaves and improve its silage quality.(4)The genomic sketch of strain WGX143 was determined.Its genome length was 3 1 8940bp.The strain WGX143 was identified as Lactobacillus plantarum subsp.plantarum by cluster analysis of 16SrRNA sequence and genomic alignment.The genome was annotated by GO,KEGG and COG through bioinformatics analysis.There are 9749 GO annotated genes,41 73 biological process genes,2848 cell group classified genes and 2728 molecular function genes;1565 KEGG annotated genes,976 metabolic pathway genes.77 cell process pathway genes,173 genetic information processing pathway genes,68 human disease pathway genes,236 environmental information processing pathway genes and 35 biological system pathway genes.There are 2565 COG annotated genes,of which 736 have unknown functions,which can be used as targets for further exploration in the future. |
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