Rubber tree Transcriptome. Hevea brasiliensis

Heterosis refers to the phenomenon that the F1 hybrid exhibits greater biomass, speed of development, and fertility than both parents. Although heterosis has been widely exploited in plant breeding, the molecular mechanisms underlying it are not well understood. The hybridization parents, PR 107 and RRIM 600, generate a growth heterotic F1 hybrid (BT 3410) and a growth weakness F1 hybrid (WC 11). Here we analyzed the characterization of >23 thousand single nucleotide polymorphisms (SNPs) identified in this study. We found that growth heterosis in F1 hybrid indicated significantly higher SNP heterozygosity in contrast to its parents and the other hybrid. The transcriptome-wide gene expression patterns were analyzed in two hybrid-parent triads. In growth heterotic hybrid, 1092 (49.95%) and 1094 (50.05%) genes indicated clear underdominance or overdominance, respectively. As for growth weakness hybrid, 160 genes (17.35%) exhibited additive model. A large proportion of genes (78.2%, 721 of 992) showed low- or high-parent dominance models. In addition, 8 (0.87%) genes showed clear overdominance and 33 (3.58%) showed clear underdominance. The altered expression patterns of differently expressed genes involved in response to stimulus and metabolic process GO terms as well as carbohydrate metabolism pathway may contribute to rubber tree seedlings heterosis and weakness. It is the first time that heterosis is systematically reported in rubber tree. Our findings bring new insights into our understanding of growth heterosis of rubber tree and may benefit rubber tree breeding.