K. Pinyopusarerk

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.

Variation in growth of Eucalyptus camaldulensis provenances in Thailand

Variation in the growth of a wide range of Eucalyptus camaldulensis germplasm was evaluated in 2-year-old provenance/progeny trials planted on three different sites in Thailand. The trials compared 315 families, of which 305 families came from 32 provenances representing five regions in northern Australia and ten families from selected trees in the local land race representing Thailand. Significant differences (P < 0.001) in height, diameter and volume per tree were found between regions, provenances within regions and families within provenances. Overall, growth of provenances from Queensland and Thailand was found to be superior to that of sources from the Northern Territory and Western Australia. Provenances from the Petford region, especially the seed source from Petford Bridge, have performed well but so did many other Queensland provenances—Wrotham Park, Lynd Junction and Healeys Yard from the Walsh-Mitchell River catchment; Gilbert River near the Gulf of Carpentaria; Kennedy River and Morehead River on Cape York Peninsula. There was a significant and consistent negative trend west to east in volume growth between provenances within the Petford region; provenances to the western extremes of the region grew more vigorously than those to the east. There is a need for a rigorous specification of the boundaries of Petford provenance when selecting seed sources for Thailand.

Range-wide provenance variation in growth and morphological characteristics of Casuarina equisetifolia grown in northern Australia.

Abstract Variation in 14 growth and morphological characteristics was assessed in a 30-month-old range-wide provenance trial of Casuarina equisetifolia in Weipa, north Queensland, Australia. The trial compared 59 provenances from throughout the species’ occurrence in four broad regions, i.e. natural occurrences in Australia/the Pacific, natural occurrences in South-East Asia, introduced populations in Asia and introduced populations in Africa. The following characteristics were assessed: axis persistence; stem straightness; density, thickness, angle and length of permanent branches; length and thickness of deciduous branchlets; stem and foliage damage; flowering and fruiting; and height and diameter growth. There were significant differences between provenances in most of the characteristics assessed. Principal component analyses suggested a pattern of geographic variation among provenances from the natural distribution, with provenances in Australia and the Pacific Islands forming a separate group from those in South-East Asia. No one provenance showed superior performance for all the characteristics, suggesting that inter-provenance hybridisation may be useful in genetic improvement programs. Most provenances from Malaysia and Thailand grew vigorously but lacked stem straightness while some Kenyan seedlots, though inferior in growth, were superior in stem form. The wide geographic range and extensive cultivation of the species offer great potential for selection of genetic material for tree improvement programs.

Geographic variation in seedling morphology of Chukrasia species

Seed collected from 23 native provenances of Chukrasia A.Juss. and one Australian land race was used to study geographic variation in seedling morphology under temperature-controlled glasshouse conditions. Twenty-four variates were measured for each seedling and the resultant data subjected to univariate and multivariate analyses. The multivariate analyses effectively separated the Chukrasia genus into three different groups or eco-geographical clusters. The most important characteristics that separated the groups were bark structure, leaf type and midrib colour. The first group, provenances from China, Laos, Malaysia, Vietnam and the Australian land race, is characterised by smooth bark, pinnate or intermediate leaves and reddish-green to greenish-red midrib. The second group, provenances from Myanmar and Thailand, is characterised by rough bark, mainly bipinnate leaves and green midrib. The third group, provenances from Sri Lanka, is characterised by rough bark, bipinnate leaves and red midrib. The study clearly shows Chukrasia to be a polymorphic species comprising at least three ecotypes or possibly three ecospecies. A study of allozyme variation may better reveal the systematics within the genus.

Genetic variation and structure of native and introduced Casuarina equisetifolia (L. Johnson) provenances

Abstract Casuarina equisetifolia is an important tree species in tropical/subtropical zones of Asia, the Pacific and Africa. In this study, 220 individuals from seven native provenances and eleven introduced provenances of C. equisetifolia were analyzed to assess the genetic variation and structure using amplified fragment length polymorphism (AFLP) markers. A total of 465 bands were obtained by eight primer pairs, among which 153 were polymorphic. The mean NEI’s gene diversity H = 0.2113 calculated for 18 provenances and the total gene diversity HT = 0.4065 calculated for native provenances suggested abundant variation within provenances and species. High genetic divergence coefficient (GST = 0.4737) and low gene flow (Nm = 0.5555) detected among native provenances suggesting high differentiation of C. equisetifolia. An AMOVA analysis for native provenances revealed a high proportion (46.07%) of the total genetic variation distributed among provenances. The UPGMA clustering (r = 0.8028) and the Mantel test (r = 0.0716) for native provenances showed there was no correlation among genetic relationships and geographical distribution. The genetic information provided important implications for the future conservation and breeding programs of C. equisetifolia.

Reproductive biology and breeding system in Casuarina equisetifolia (Casuarinaceae) – implication for genetic improvement

Understanding the reproductive biology of plant species is essential for successful domestication and genetic improvement programs. Casuarina equisetifolia L. is an important plantation species in China and India but information on reproductive biology is limited. To address this issue, grafted ramets of C. equisetifolia were used to study floral biology, breeding system and progeny performance. The female floral longevity of C. equisetifolia reached 28.4 days under non-pollination conditions, which was significantly longer than that of supplementary pollination (5.5 days) and open pollination (12.2 days), implying successful pollination would accelerate senescence of female flowers. Higher fruit set (88.8%) and seed set (35.7%) under supplementary pollination were obtained, compared with 75.9% and 21.7%, respectively, under open pollination, although there were no fruit set and seed set under non-pollination conditions. Pollen limitation was evident based on pollen limitation index (0.39) in seedling plantations of C. equisetifolia. Selfed seedlings had low height and diameter growth in both nursery and field trials and markedly lower survival in field trial, indicating inbreeding depression. Microsatellite-based estimates of selfing rate of open pollinated, monoecious individuals was 42%, suggesting that monoecious C. equisetifolia individuals are self-compatible, and that the breeding system should be classified as facultative xenogamy.

Geographic variation in seedling morphology of Casuarina equisetifolia subsp. equisetifolia (Casuarinaceae).

Seeds collected from 28 natural provenances and introduced populations of Casuarina equisetifolia subsp. equisetifolia L. from Oceania, Asia and Africa were used to study geographic variation in growth and morphology of nursery-grown seedlings. Ten characteristics related to growth and branching habit were measured for each seedling and the resultant data subjected to univariate and multivariate analyses. In general, seedlings from Oceania grew more slowly, were more densely branched with fine and upright branching, and had fewer teeth per whorl than those from other areas. Cluster analysis effectively separated Oceania from Asian natural provenances, and revealed the probable original sources of introductions to different parts of Asia and Africa. Further investigation into the pattern of variation through molecular characterisation of genetic material from all major regions of distribution is warranted in order to better understand the genetic relationships and enhance more efficient utilisation of this important casuarina species.

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

Key messageISSR characterization ofChukrasiapopulations 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.AbstractThere 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.

A Novel Approach for Controlled Pollination in Casuarina equisetifolia

Abstract Casuarina equisetifolia is an important tree species in the tropical and subtropical zones of Asia, Africa and the Pacific. There is an increasing interest in producing intra- and inter-specific hybrids of casuarina species. Conventional bagging controlled pollination method yielded very low fruit set and poor seed germination. High temperature and humidity in the pollination bags appeared to have instigated unfavorable conditions for pollination and fertilization mechanism. In this study, a novel approach was developed by conducting pollination in closed chambers which functioned like pollination bags. Fruit set and seed germination rate increased from 7.0% to 89.9%, and 8.1% to 51.8% respectively compared with the conventional bagging controlled pollination method. Based on the results, a controlled pollination glasshouse with 10 separated chambers has been designed to produce multiple hybrid combinations in a single pollination procedure.