Exploring the genetic basis of heterosis in eucalypt growth based on transcriptome analysis

Background The fundamental way to solve the problems of single species, poor stress resistance, and low yield in Chinese eucalypt plantations is to scientifically utilize the heterosis of eucalypt and select new varieties with rich genotypes. In order to reveal the genetic mechanism of the formation of heterosis in eucalypt growth, based on previous research on the relationship between eucalypt heterosis and parental combining ability, we selected two artificial hybrids 18H167 (T15 × U3423) and 19H74 (U3423 × U6) with significant differences in birth length and similar parental relationships as the research objects. Results Transcriptome analysis using RNA-seq technology showed that the correlation between gene expression levels indicated that the male parent had a greater impact on the heterosis of eucalypt growth. Based on GO and KEGG annotations, GSEA enrichment and WGCNA analysis identified 8 pathways and 7 Hub genes that may be related to growth differences in eucalypt. These candidate pathways are related to genes and ribosomal subunits, extracellular regulatory mechanisms, and three amino acid synthesis pathways. From their biological functions, the growth differences of eucalypt may be strongly correlated with their ability to adapt to environmental stress. AS analysis showed that the AS events of the two hybrids were significantly higher than those of their parents, with SE events possibly related to growth disadvantage and RI events more likely to be related to growth advantage. Conclusions This study provides a more in-depth exploration of the formation mechanism of heterosis in eucalypt growth, which is expected to guide the selection of parents in eucalypt hybrid breeding. The discovery of candidate genes/pathways provides genetic information for eucalypt genome or molecular marker assisted selection breeding.