Betula alnoides is a valuable timber species with wide ecological adaptability in Southeast Asia and southern China. There are more than 150,000 ha of B. alnoides plantations in China until now. However, heavy differentiation in growth and quality traits with low productivity are usually seen in the practice. Elite germplasm are thus urgently needed for this species. Here growth and quality traits for 199 families of 25 provenances were assessed at four sites when 10–15 years old to estimate genetic parameters and reveal genotype by environment (G × E) interaction, and screen out superior provenances and families for plantation forestry of B. alnoides. The growth and quality performances of provenances varied with sites. Significant site, provenance, family and provenance-site effects were revealed for most growth and quality traits, while significant family-site effects were only observed in crown width (CW) and crown shape (CS), inferring that there existed significant G × E interaction. The provenance repeatability ( $h_p^2$ ) and family heritability ( $h_f^2$ ) of all tested traits ranged from 0.026 to 0.636 and 0.148 to 0.578, respectively. Stem volume showed the highest genetic and phenotypic coefficients of variation (GCV, PCV) among all traits at each site. The diameter at breast height (DBH), tree height (H), height to live crown base (HCB) and CW were strongly correlated with other traits, and were also under relatively higher genetic control and had stronger discriminating ability on genotype differences. Through biplot analyses of main genotypic effect and G × E interaction (GGE) for these traits, five provenances and 20 families were screened out with selection ratio of 20 % and 10% at provenance and family level, respectively. The genetic and realized gains at provenance level ranged from 0.25% to 2.01% and 2.43% to 14.84%, and those at family level ranged from 0.85% to 21.22% and 5.76% to 36.71%, respectively. The findings lay a foundation for subsequent study on genetic improvement and breeding of this species, and application of the superior provenances and families will greatly increase the productivity of its plantations in practice.

Premise of the study: Microsatellite markers were developed for Vatica mangachapoi (Dipterocarpaceae), an endangered species indigenous to Southeast Asia and southern China.Methods and Results: Twenty microsatellite markers, including 12 polymorphic markers, were identified from V. mangachapoi using high‐throughput sequencing. Polymorphism at each marker was evaluated using 87 individuals from three natural populations. The number of alleles per polymorphic locus ranged from six to 15, and the observed and expected heterozygosity varied from 0.000 to 0.926 and from 0.177 to 0.864, respectively. These markers were transferred successfully to the endangered species V. guangxiensis.Conclusions: These markers may be used to investigate the genetic diversity and gene flow of V. mangachapoi and V. guangxiensis.

Betula alnoides is a fast-growing valuable indigenous tree species with multiple uses in the tropical and warm subtropical regions in South-East Asia and southern China. It has been proved to be tetraploid in most parts of its distribution in China. In the present study, next generation sequencing (NGS) technology was applied to develop numerous SSR markers for B. alnoides, and 64,376 contig sequences of 106,452 clean reads containing 164,357 candidate SSR loci were obtained. Among the derived SSR repeats, mono-nucleotide was the main type (77.05%), followed by di- (10.18%), tetra- (6.12%), tri- (3.56%), penta- (2.14%) and hexa-nucleotide (0.95%). The short nucleotide sequence repeats accounted for 90.79%. Among the 291 repeat motifs, AG/CT (46.33%) and AT/AT (44.15%) were the most common di-nucleotide repeats, while AAT/ATT (48.98%) was the most common tri-nucleotide repeats. A total of 2549 primer sets were designed from the identified putative SSR regions of which 900 were randomly selected for evaluation of amplification successfulness and detection of polymorphism if amplified successfully. Three hundred and ten polymorphic markers were obtained through testing with 24 individuals from B. alnoides natural forest in Jingxi County, Guangxi, China. The number of alleles (N_A) of each marker ranged from 2 to 19 with a mean of 5.14. The observed (H_O) and expected (H_E) heterozygosities varied from 0.04 to 1.00 and 0.04 to 0.92 with their means being 0.64 and 0.57, respectively. Shannon-Wiener diversity index (I) ranged from 0.10 to 2.68 with a mean of 1.12. Cross-species transferability was further examined for 96 pairs of SSR primers randomly selected, and it was found that 48.96–84.38% of the primer pairs could successfully amplify each of six related Betula species. The obtained SSR markers can be used to study population genetics and molecular marker assisted breeding, particularly genome-wide association study of these species in the future.

Erythrophleum fordii Oliv. is a valuable rosewood species indigenous to the tropical and warm sub-tropical zones of Vietnam, Laos, and South China. The natural forests have been heavily fragmented mostly due to over-exploitation and over-utilization, and alteration to croplands and fast-growing plantations. Therefore, it has been included in the IUCN Red List of Endangered Species as an endangered species. In the present study, genetic diversity and population genetic structure of 11 populations were estimated by SSR makers in South China. Five high polymorphic loci were studied with a total of 34 alleles, among which, seven were private alleles. The mean number of alleles per locus (A), the mean number of efficient alleles per locus (Ae), the observed (Ho) and expected (He) heterozygosity, and Shannon’s index (I) of the 11 populations were 3.40, 2.31, 0.52, 0.56, and 0.90, respectively. Correlation analysis between genetic parameters and geographical factors showed that He and I were in significant negative correlation with longitude, indicating that genetic diversity of E. fordii reduced gradually from West to East in south China. F_IS of eight populations with above five samples was on average 0.01, most loci conformed to Hardy-Weinberg equilibrium in these populations; their genetic differentiation coefficient (F_ST) was 0.18, indicating that genetic differentiation among populations was relatively low and there existed 18% genetic variation among populations. Gene flow (Nm) between these populations was 1.28. The Mantel test showed that genetic distance was not significantly correlated with geographical distance (p > 0.05). It was concluded that populations with high genetic diversity or private alleles, especially Longmen, Wuming and Pingxiang populations should be a priority for in situ conservations, meanwhile more populations and as many families as possible in each population should be collected for ex situ conservations of germplasm resources of this species in the future.

The diverse topographies of high mountains and deep river valleys in Yunnan, China create geographic and environmental barriers that promote intraspecific genetic differentiation. This study employed amla (Phyllanthus emblica L.) to reveal the effects of geographic and environmental isolation on genetic differentiation of plant species. We sampled 18 natural P. emblica populations from upstream to downstream in the Longchuan, Nu, Lancang, Yuanjiang and Jinsha Rivers valleys (three or four per valley) in 2017. Genetic diversity and structure of P. emblica were assessed across these populations using 16 SSR loci developed, and analyzed with GenAlEx, ATetra, and STRUCTURE software packages. Ecological niche modeling (MaxEnt) estimated its historical and contemporary potential geographic distribution patterns, and redundancy analysis (RDA) identified key environmental factors influencing genetic diversity. P. emblica exhibited high genetic diversity, primarily influenced by mean temperature of the warmest quarter (Bio10) and precipitation of the warmest quarter (Bio18). STRUCTURE analysis revealed a distinct division of these populations into western and eastern groups, closely aligned with the Tanaka-Kaiyong Line. Significant genetic differentiation existed between the western and eastern populations, and suggesting that long-term geographic isolation and environmental heterogeneity promote genetic differentiation and local adaptation of this species. MaxEnt modelling indicated a significant expansion in the potential habitat of P. emblica from the Last Glacial Maximum (LGM) to the present, likely due to climate warming. Our findings provide evidence for genetic differentiation in P. emblica driven by geographical and environmental isolation, and offer critical insights into developing effective conservation and utilization strategies for its genetic resources.