Widely distributed in the alpine sandy grassland in east Qinghai-Tibet Plateau (QTP), Kengyilia melanthera is considered as an ideal pioneer grass for the restoration of degraded and desertification grassland in the region. Under the special ecological and climatic conditions in the northwest Sichuan plateau located in east QTP, it is of great significance to optimize the amount of nitrogen fertilizer for the seed production of this species. The impact of nitrogen (N) fertilizer application on seed yield and quality of K. melanthera ‘Aba’, the only domesticated variety in the Kengyilia genus of Poaceae, was investigated based on two-year field experiments in the northwestern Sichuan plateau. The results showed that with the increase of N fertilizer application, the number of tillers, number of fertile tillers, 1,000-seed weight and seed yield of this species increased likewise. The optimum N fertilizer rate deduced in the present study was 180 kg·hm⁻², where the number of fertile tillers 1,000-seed weight and seed yield reached the peak values. Interestingly, the standard germination rate, germination energy, accelerated aging germination rate, dehydrogenase and acid phosphatase activity of seeds were not affected by the increasing the input of N fertilizer. The comprehensive evaluation of membership function showed that the optimal N fertilizer treatment was 180 kg·hm⁻² both for 2016 and 2017. This study provided a certain practical suggestion for the improvement of seed production of K. melanthera in the northwest Sichuan plateau.

Elymus breviaristatus is a grass species only distributed in the southeast of Qinghai-Tibetan Plateau (QTP), which has suffered from serious habitat fragmentation. Therefore, understanding patterns of genetic diversity within and among natural E. breviaristatus populations could provide insight for future conservation strategies. In this study, sequence-related amplified polymorphism markers were employed to investigate the genetic diversity and hierarchical structure of seven E. breviaristatus populations from QTP, China. Multiple measures of genetic diversity indicated that there is low to moderate genetic variation within E. breviaristatus populations, consistent with its presumed mating system. In spite of its rarity, E. breviaristatus presented high genetic diversity that was equivalent to or even higher than that of widespread species. Bayesian clustering approaches, along with clustering analysis and principal coordinate analysis partitioned the studied populations of E. breviaristatus into five genetic clusters. Differentiation coefficients (F_st, G_ST, etc.) and AMOVA analysis revealed considerable genetic divergence among different populations. BARRIER analyses indicated that there were two potential barriers to gene flow among the E. breviaristatus populations. Despite these patterns of differentiation, genetic distances between populations were independent of geographic distances (r = 0.2197, p = 0.2534), indicating little isolation by distance. Moreover, despite detecting a common outlier by two methods, bioclimatic factors (altitude, annual mean temperature, and annual mean precipitation) were not related to diversity parameters, indicating little evidence for isolation caused by the environment. These patterns of diversity within and between populations are used to propose a conservation strategy for E. breviaristatus.

Erianthus arundinaceus is not only a candidate plant for sugarcane breeding programs, but also a potential bioenergy grass. Genetic variation that is affected by geographic environments and ploidy level is very important for the utilization of Erianthus arundinaceus. In this study, effects of geographic environments and ploidy level on genetic variation were studied through analyzing the genetic diversity, genetic similarity and cluster analysis of 46 E. arundinaceus materials from natural habitats in China by using 7 ISSRs and 15 SSRs. Results showed that: 1) Seven ISSRs generated total 66 bands, of which 77% were polymorphic bands, the Nei's genetic similarity coefficient of tested materials ranged from 0.642 to 0.904 with an average value of 0.765. Fifteen SSRs generated 138 bands, of which 81% were polymorphic bands, the Nei's genetic similarity coefficient of tested materials ranged from 0.634 to 0.963 with an average value of 0.802. The results indicated great genetic diversity existed in the tested materials. 2)The tested materials were clustered into 3 groups and 7 subgroups, which demonstrated a strong geographic effect on variation of the local E. arundinaceus, and weak relationship was found between genetic distance and geographic distance. Five tetraploid materials were not clustered together, and were clustered together with materials from similar geographical location. 3) The genetic variation and cluster results were affected by geographic landforms and environments, the gene flow was blocked by Ocean and mountains, and promoted by river. The effect of ploidy level on genetic variation was little.

Kengyilia melanthera is one of the most important forages, and has received significant attention as a desirable ecological pioneer grass for conserving grasslands and mitigating degradation pressure in a region. It is widely distributed in the alpine sandy meadow zone of the Eastern Qinghai–Tibet Plateau (QTP). Therefore, determining the optimal harvest time of this species is critical. A two-year field experiment (2016–2017) was utilized in this study to evaluate the impact of eight harvest times on the seed yield and quality of K. melanthera ‘Aba’. The results show that the fresh weight (FW), dry weight (DW), seed yield (SY), thousand-grain weight (TGW), accelerated aging germination percentage (AAGP), and dehydrogenase activity (DA) of seeds increased with the extension of harvest time in two trial years, while the water content (WC) of seeds decreased. In both trial years, the germination percentage (GEP), germination potential (GP), and acid phosphatase activity (APA) of seeds increased initially and then decreased with the extension of harvest time. The comprehensive evaluation of the membership function and hierarchical clustering revealed that the 30th day after peak anthesis was the optimal harvest time for both 2016 and 2017. During this time, FW, DW, SY, TGW, AAGP, DA, WC, GEP, GP, and APA reached their optimal value, with 0.815 g, 0.518 g, 1773.67 kg·hm⁻², 143.81%, 66%, 16.23 µg·mL⁻¹, 36.01%, 87%, 85%, and 2.50 nmol·min⁻¹ in 2016 and 0.805 g, 0.515 g, 1847.42 kg·hm⁻², 133.96%, 65%, 16.52 µg·mL⁻¹, 36.04%, 86.5%, 83.5%, and 2.55 nmol·min⁻¹ in 2017, respectively. This study uncovers several high-efficiency and long-term technological solutions for cultivating high yields and quality production of K. melanthera in East QTP.