短枝木麻黄种群苗期表型多样性评价

以来源于大洋洲原生种源区、亚洲原生种源区、亚洲引种次生区以及非洲引种次生区4个区域的20个种源短枝木麻黄种子和当年生幼苗为材料,通过种子千粒重以及幼苗苗高、地径、一级侧枝粗度、一级侧枝长度等7个性状对短枝木麻黄表型多样性进行了研究,以探讨种群苗期表型遗传差异,为短枝木麻黄早期遗传选择和遗传改良提供基本资料。结果表明:(1)短枝木麻黄种子千粒重在区域间和区域内种源间差异极显著,且千粒重具有显著的地理变异模式,随经度的增大而降低。(2)当年生幼苗苗高、地径在不同区域间及区域内种源间均存在极显著差异,其中泰国干东港种源幼苗生长最好(苗高76.6cm,地径4.64mm),而种源汤加的幼苗生长最差(苗高28.3cm,地径2.58mm)。(3)当年生幼苗一级侧枝粗度、一级侧枝长度、二级侧枝长度、每小枝节数和齿叶数在不同区域间及区域内种源间均存在极显著差异,其中齿叶数在区域间的变异系数最大(82.15%)。(4)通径分析表明,一级侧枝长度对苗高具有显著的正向影响作用,而一级侧枝粗度和二级侧枝长度对地径具有显著正向影响作用,它们可作为短枝木麻黄优良新品种筛选的参考因子。     

Improved Tolerance of Teak (Tectona grandis L.f.) Seedlings to Low-Temperature Stress by the Combined Effect of Arbuscular Mycorrhiza and Paclobutrazol

Low-temperature damage is a common problem for tropical and subtropical plants during their early-growth stage. In this study, an experiment with a L₁₈ (2¹?×?3⁷) mixed orthogonal array in a greenhouse was conducted to determine whether arbuscular mycorrhizal fungi (AMF) inoculation and paclobutrazol (PBZ) application through foliar spray would enhance the chilling tolerance of teak seedlings. One-month-old seedlings of clones 8301, 7544, and 7552 from a Myanmar provenance propagated by tissue culture techniques were inoculated with Glomus versiforme and cultivated for 6?months. The foliar surface of both mycorrhizal and nonmycorrhizal treated plants was sprayed with PBZ at concentrations of 0, 50, and 100?mg?l^?1 once a week for 3?weeks prior to exposure to low temperatures of 6, 3, and 0°C for 12?h in an artificial climate chamber, followed by 12?h of recovery at 20°C room temperature. AMF colonization significantly promoted height and RCD growth and dry biomass accumulation of shoot and root. Under low-temperature stress, AM symbiosis increased leaf chlorophyll content by 22.8%, soluble protein content by 19.6%, superoxide dismutase (SOD) activity by 10.6%, and peroxidase (POX) activity by 9.5%, whereas malondialdehyde content was decreased by 14.1%. Both AMF colonization and the foliar spray PBZ at 50 and 100?mg?l^?1 were capable of alleviating the damage caused by low-temperature stress on teak seedlings by increasing the photosynthetic pigments, accumulation of osmotic adjustment compounds, and antioxidant enzyme (SOD and POX) activity, and by decreasing membrane lipid peroxidation. AMF colonization and foliar spraying of PBZ at 50?mg?l^?1 produced a positive interaction and appears to be a good way to enhance chilling tolerance of teak seedlings experiencing stress at 6, 3 and 0°C for 12?h.     

Genetic diversity and genetic relationships of Chukrasia spp. (Meliaceae) as revealed by inter simple sequence repeat (ISSR) markers

Key message

ISSR characterization of Chukrasia populations from the natural range revealed two distinct groups of populations consonant with morphological differentiation. Results suggest the current taxonomic classification of the genus should be reviewed.

Abstract

There are different views as to whether the genus Chukrasia (Meliaceae) consists of one species, C. tabularis, or two species C. tabularis and C. velutina. Despite a clear pattern of variation in many morphological characteristics such as leaves and bark, some authors regard the latter merely an ecotype of the former in seasonal forest. In the present study, we used ISSR markers to determine the genetic diversity and population structure among 23 Chukrasia subpopulations from across the natural range in Asia. Molecular analysis clearly differentiated two distinct groups of subpopulations, corresponding to the putative species, as well as well-defined subpopulations corresponding to geographic regions within the two groups. The molecular results are in concordance with morphological differentiation and corresponded to the two recognized taxa. The present study suggests that current taxonomic classification of the genus Chukrasia should be reviewed.     

Casuarina research and applications in China

Casuarina trees are planted along the coastal area of the South China as windbreaks, and in agroforestry systems and for wood and fuel wood production. At present, casuarina plantations cover about 300,000 hectares. Casuarina equisetifolia, C. cunninghamiana, C. glauca and C. junghuhniana are the most commonly planted species. A simple technique for the mass propagation of casuarina seedlings has been developed using cuttings rooted in water. A series of field trials have been carried with various Casuarina species, provenances and clones to screen for adaptability to biotic and abiotic stresses in different areas of China. Experiments conducted in the nursery, glasshouse and field showed that ectomycorrhizal (ECTM), arbuscular mycorrhizal (AM) fungi or Frankia symbiotic associations play an important role in improved growth of managed casuarina plantations.