| Wildrye is one of the most important forage plants on the Qinghai-Tibet plateau. This paper were studied Elymus from three aspects (1) Genetic diversity of 9 Tibet Elymus populations with 8 control groups was studied by amplified fragment length polymorphism (AFLP) in order to evaluate the genetic diversity, quantity and distribution of germplasm resources of the Tibet wild Elymus L. on molecular level and utilization in the evaluation of the genetic diversity of Elymus L., (2) quantify the seed yield, apparent N recovery efficiency (ANRE), and N utilization efficiency (NUE) in response to the rate of the applied N, and (3) evaluate the rumen degradation characteristics of main nutrients (DM, CP, OM, NDF, ADF) of 15 forages in Tibet using six rumen-cannulated'Pengbo'semi-wool rams. The main results were as follows:1. Genetic Diversity(1) Based on the previous research on AFLP reaction system and reaction procedure, the AFLP silver-staining analysis system suitable for genomic DNA of Elymus L.was established for the first time.(2)AFLP marker: 16 primer combinations were used for polymorphism selection and 3 primer combinations produced specifically polymorphism products. Each primer combination amplified 70-83 loci. A total of 232 sites were observed, among them 206 sites are polymorphism sites. Polymorphism markers generated percentage of 88.79%, the average number of polymorphism site produced by each primer combination was 68.67. Genetic identity ranged from 0.284 to 0.955 among the 17 populations. The cluster analysis with UPGMA showed that when genetic identity is 0.59, the 17 populations could be divided into 4 groups.2. Nitrogen Utilization(1)Variation in total above-ground plant biomass was associated with N treatment, and was increased by N fertilization with a larger N effect (P < 0.01). The best seed yield response was obtained in the 240 kg N ha-1 treatment. Seed yield in plants receiving 320 kg N ha-1 was slightly lower, although straw yield increased significantly.(2)Nitrogen application rate had a significant effect on ANRE (P < 0.05), and a general decrease in ANRE was observed as N fertilization rate increased in both species. In both species ANRE showed a linear response to N fertilization. ES showed a higher mean ANRE than EN, but the difference in ANRE between ES and EN at maturity was not significant (p > 0.05). However, the interaction between N treatment and species on ANRE was significant (P < 0.05).(3)The N treatment significantly affected wildrye NUE (P < 0.01), which tended to decline linearly with increasing N rate. At maturity, both species had a significant effect on NUE (P < 0.01). Variation in NUE existed due to observed differences in plant N concentrations; EN showed a higher NUE (28.47 kg DM kg-1 N) than ES (24.82 kg DM kg-1 N), and the difference between ES and EN at maturity was significant (P < 0.01). There was also a significant interaction (P < 0.01) between N treatment and species on NUE at maturity. Compared with E. nutans (EN), E. sibiricus (ES), achieved higher total biomass, N concentration and N uptake, but a lower NUE, which indicated that E. nutans is an N-efficient species.3. Assessment of feeding value(1) The degradability of DM, OM, CP, NDF and ADF in rumen of the forages increased as incubation time and stabled within 48h.(2)When the k is 0.02, the effective degradation of DM were range from 29.23 to 52.46%, the effective degradation of OM were range from 30.37 to 51.78%, the effective degradation of CP were range from 32.28 to 55.81%, the effective degradation of NDF were range from 27.59 to 52.61%, the effective degradation of ADF were range from 24.51 to 48.65%. From the point of view of the rapidly solube fraction, potential degradable fraction and effective degradable fraction for DM, OM and CP, wildrye performed better than other grass forages.(3)The content of crude protein of Elymus increased as the altitude increasing, while the content of neutral detergent fibre was decreased. Accordingly, the forage with high nutritional value had high degradability in sheep.
|
PDF Full Text Request