Changjun Bai

Grassland development in tropical and subtropical southern China

China’s 79 million ha of tropical and subtropical grasslands represent a significant national forage resource with a potential for further development for sustainable livestock production. The species rich original forest vegetation has been converted through natural and human activities to secondary forest, grassland and agricultural land. The grasslands which include savannah, shrubland, coppice forest and arable land sown with exotic legumes and grasses are expected to become China’s third largest livestock production zone. Despite degradation the grasslands retain a high level of biodiversity which has been preserved in germplasm depositories with on-going collection expeditions throughout south China. Productivity of natural grasses is moderate (<5 t DM/ha) but can be increased significantly by augmenting with Stylosanthes and other introduced legumes adapted to the infertile or acidic soils and seasonal rainfall. Stylosanthes species which is used for grazing, green chop or leaf-meal production, as well as a cover crop in orchards, plantations and forest are successful because they are simple to establish and deliver immediate profits to farmers through improved livestock production or sale of forage for leaf meal manufacture. On-going plant breeding programs are delivering new higher yielding legume and grass cultivars with disease resistance and acid soil tolerance. They are expanding selection priorities to address environmental concerns (e.g. soil acidifying legumes) and to meet the needs of new integrated production systems. Introduced legumes and grasses have provided benefits to the environment through improved soil fertility, reduced soil erosion, increased infiltration rates and reduced weed invasion. Experts believe that the southern tropical and subtropical grasslands still have the capacity to safely increase production and contribute significantly to the improvement of the regional ecosystem. However, this can only be achieved if current programs on germplasm preservation, breeding new cultivars and developing management systems for integrated production systems need to be balanced with work precision livestock management and promotion of monitoring individual animal performance to achieve improved livestock production efficiency.

Genetic Analysis of 430 Chinese Cynodon dactylon Accessions Using Sequence-Related Amplified Polymorphism Markers

Although Cynodon dactylon (C. dactylon) is widely distributed in China, information on its genetic diversity within the germplasm pool is limited. The objective of this study was to reveal the genetic variation and relationships of 430 C. dactylon accessions collected from 22 Chinese provinces using sequence-related amplified polymorphism (SRAP) markers. Fifteen primer pairs were used to amplify specific C. dactylon genomic sequences. A total of 481 SRAP fragments were generated, with fragment sizes ranging from 260–1800 base pairs (bp). Genetic similarity coefficients (GSC) among the 430 accessions averaged 0.72 and ranged from 0.53–0.96. Cluster analysis conducted by two methods, namely the unweighted pair-group method with arithmetic averages (UPGMA) and principle coordinate analysis (PCoA), separated the accessions into eight distinct groups. Our findings verify that Chinese C. dactylon germplasms have rich genetic diversity, which is an excellent basis for C. dactylon breeding for new cultivars.

Carex diaoluoshanica (Carex sect. Lageniformes, Cyperaceae), a new species from Hainan, China.

Carex diaoluoshanica, a new species of Carex sect. Lageniformes from Hainan, China, is described and illustrated. The new species is similar to C. breviscapa but differs in having wider leaves with the leaf base gradually narrowed, 5–10 cm long and petiolelike, culms subfiliform, with only two spikes, the lateral female spikes from near the culm base.

High Salt Tolerance of a Bradyrhizobium Strain and Its Promotion of the Growth of Stylosanthes guianensis

Salinity is a serious limiting factor for the growth of rhizobia. Some rhizobia are tolerant to salt stress and promote plant growth, but the mechanisms underlying these effects are poorly characterized. The growth responses and osmoprotectants in four Bradyrhizobium strains were examined under salt stress in this study. Two-dimensional electrophoresis (2-DE) and mass spectrometry were conducted to investigate protein profiles in rhizobia exposed to salt stress. Subsequently, salt tolerance in stylo (Stylosanthes guianensis) inoculated with rhizobia was further detected in hydroponics. Results showed that the Bradyrhizobium strain RJS9-2 exhibited higher salt tolerance than the other three Bradyrhizobium strains. RJS9-2 was able to grow at 0.35 M NaCl treatment, while the other three Bradyrhizobium strains did not grow at 0.1 M NaCl treatment. Salt stress induced IAA production, and accumulation of proline, betaine, ectoine, and trehalose was observed in RJS9-2 but not in PN13-1. Proteomics analysis identified 14 proteins regulated by salt stress in RJS9-2 that were mainly related to the ABC transporter, stress response, and protein metabolism. Furthermore, under saline conditions, the nodule number, plant dry weight, and N concentration in stylo plants inoculated with RJS9-2 were higher than those in plants inoculated with PN13-1. These results suggest that the tolerance of RJS9-2 to salt stress may be achieved by the coordination of indole-3-acetic acid (IAA) production, osmoprotectant accumulation, and protein expression, thus promoting stylo growth.

Carex jianfengensis (Carex sect. Rhomboidales, Cyperaceae), a New Species from Hainan, China

A new species of Carex sect. Rhomboidales, C. jianfengensis, is described and illustrated from Hainan, China. The new species is similar to C. zunyiensis but differs in having involucral bracts sparsely hispid and with ca.1 cm long sheaths; inflorescence with 4 spikes, terminal spike ca. 2.5 cm long, lateral spikes 2–3.5 × 0.7–1 cm; staminate glumes narrowly ovate, ca. 5 mm; pistillate glumes triangular-lanceolate, 5–7 mm; perigynia 6–8 × 3 mm and pubescent on veins; nutlet 4–5 mm long, rhombic-ovoid, trigonous, base with shortly stipitate, apex abruptly contracted into a erect short beak, and not expanding into an annulate orifice.