Inefficient evaluation methods for germplasm traits severely hinder the development, utilization, and preservation of germplasm resources. Addressing the current lack of high-throughput measurement techniques for the traits of Caulerpa lentillifera, this study established a nondestructive quantification method for the spherical branchlets count of C. lentillifera based on CT imaging and the PointNet++ model. First, X-CT systems were employed to perform 3D imaging of 196 fronds, enabling rapid and nondestructive acquisition of their three-dimensional structural data. The obtained data were converted into 3D point cloud format, and a dataset was constructed by manually annotating the point cloud data of 196 fronds using the open-source software CloudCompare. The dataset was partitioned into training, validation, and test sets at a ratio of 7∶2∶1. Through model training based on the point cloud segmentation network PointNet++, along with multiple rounds of refined data processing and hyperparameter tuning, an optimal model was successfully developed. This model achieved high-throughput and accurate quantification of spherical branchlets on fronds. Finally, the model was tested on C. lentillifera accessions with densely clustered spherical branchlets, demonstrating high goodness-of-fit, with R², RMSE, and MAPE values of 0.927 6, 4.23, and 6.37%, respectively, confirming the feasibility of this technique. This study provides an effective tool for morphological trait measurement in C. lentillifera.

In order to address the paucity of genetic loci associated with growth traits in the genetic breeding studies of Neopyropia yezoensis, the genome-wide association study (GWAS) was conducted for 4 important growth traits in gametophytes of N. yezoensis. One hundred and thirty thalli of N. yezoensis with single genotype were cultured under the same environment. Four growth-related phenotypic values of thallus length, thallus width, fresh mass and dry mass were measured. Study revealed that the coefficient of variation of different growth traits of thalli ranged from 32.63% to 50.95%, and there were significant correlations among the four traits. The genotype of each individual were obtained by whole genome re-sequencing. After quality inspection of the re-sequencing data, a total of 405 999 high-quality SNPs were obtained, of which 53 077 sites were in the exon region, and the ratio of SNPs transitions to translocations was 1.23. Population structure analysis found that the population in this work could be divided into 4 subgroups, and there were obvious genetic differences between any two different subgroups. The subgroups division were not in accordance with geographical location. The relatively distant phylogenetic relationship among the individuals and the short range of LD decay distance indicated that the genetic variation was relatively rich in the population. The mixed linear model (Q+K) was used to screen the associated loci of traits. A total of 90 significant SNP markers were detected, of which 67 loci were correlated with thallus length, 17 loci were correlated with thallus width, 4 loci were correlated with fresh mass, and 2 loci were correlated with dry mass, which could explain 16.12% to 24.85% of the observed phenotypic variation. A total of 39 candidate genes were identified within a 20 kb range upstream and downstream of the SNP site with significant association. The gene functions involved cell proliferation, control of cell metabolic pathways, and regulation of plant growth and development. This study furnishes a set of candidate genetic markers and crucial evidence for molecular breeding of N. yezoensis.