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.

The rainy seasons have been becoming irregular and unpredictable under global warming now. This usually makes seedling preparation more difficult to match transplanting. Here applications of plant growth regulators, paclobutrazol (PBZ) and gibberellins (GA₃) were studied with two trials to regulate growth of Betula alnoides Buch. Ham. ex D. Don container seedlings for the purpose of improving their quality when transplanting delayed. In the first trial five treatments (coded as P1 to P5) were laid out with total dosages of 0 mg (control), 2 mg, 6 mg, 10 mg and 20 mg PBZ per seedling to assess inhibitory effects of PBZ on growth of B. alnoides seedlings. After four and a half months, the second trial was carried out on the seedlings from the optimized PBZ treatments to detect growth recover of the seedlings by GA₃, in which four treatments were arranged with GA₃ dosages being 0, 1/10, 1/5 and 1/3 of the optimized paclobutrazol amounts applied. PBZ applications resulted in a significant decrease of height and root collar diameter growth since approximately one and two months after being treated, respectively. Among these treatments, P5 was the best one in controlling seedling growth, and its inhibitory effects lasted more than four and half months. PBZ treatments differed obviously in total seedling biomass from the control at 96 and 132 days after treatment (dat), and allocated more ratio of biomass into roots. Their root/shoot ratios increased and leaf areas decreased considerably with increasing PBZ dosage, while only P5-treated seedlings showed remarkable difference from the control in chlorophyll contents. The GA₃ recovery showed that 15-day height increments of seedlings treated with GA₃ were twice more than that without GA₃ treatment, and did not differ significantly from the control without PBZ and GA₃ treatment. It is concluded that the combined application of PBZ and GA₃ can be recommended as a potential tool for regulating growth of B. alnoides seedlings, making it flexible to growing seedlings in the nursery.

Lithocarpus litseifolius is a medicinal tea plant recognized for its sweet flavor and anti-diabetic properties, but its limited leaf yield under cultivation restricts its economic sustainability. Melatonin (MLT) is a multifunctional plant growth regulator, but its roles in leaf growth under normal conditions remain not fully understood. Herein, we investigated the effects and mechanisms of foliar-applied MLT on L. litseifolius seedlings, including growth indices, phytohormone profiles, photosynthetic characteristics, and transcriptome alterations. The 100 μM MLT treatment significantly enhanced leaf dry weight by 33.8% and leaf dry matter content by 22.2% compared to the control group. MLT decreased both free and bound abscisic acid (ABA), while increasing gibberellins (GAs), 5-deoxystrigol, auxins (e.g., IAM), and cytokinins (e.g., cZ9G). Additionally, exogenous MLT improved photosynthetic rate, stomatal conductance, chlorophyll content, and soluble sugars in leaves. RNA-seq revealed that MLT up-regulated DEGs involved in hormone biosynthesis and signaling (CYP707A, BAK1, D14, CCD1, and IAA6), photosynthesis (PsbC/B, PetH, PsaB, and ATPase β), and sugar metabolism (WAXY, glgC, and otsB). Our results demonstrate that MLT promotes leaf dry matter accumulation through coordinated phytohormone homeostasis, photosynthetic enhancement, and transcriptional regulation, offering a cost-effective strategy to improve leaf yield in L. litseifolius.